The surgical approach to congenital heart disease

The surgical approach to congenital heart disease

is Assistant Professor of Surgery in the Department of Cardiac and Thoracic Surgery of Vanderbilt University School of Medicine and Chief of the Cardi...

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is Assistant Professor of Surgery in the Department of Cardiac and Thoracic Surgery of Vanderbilt University School of Medicine and Chief of the Cardiothoracic Surgical Service at the Nashville Veteran’s Administration Medical Center. He received his medical education at The Johns Hopkins University School of Medicine, and his residency in general and thoracic surgery was at The Johns Hopkins Hospital. He spent two years as a Clinical Associate in The Clinic of Surgery, National Heart, Lung, and Blood Institute, National Institutes of Health. Following completion of his training Dr. Merrill spent one year as a Senior Registrar on the Thoracic Unit, The Hospital for Sick Children, Great Ormond Street, London. His principal clinical and research interests are in thoracic and pediatric cardiac surgery.

is Professor and Chairman of the Department of Cardiac and Thoracic Surgery of Vanderbilt University School of Medicine. After graduating from Baylor College of Medicine he obtained his residency training at The Johns Hopkins Hospital and at The Clinic of Surgery, National Heart, Lung, and Blood Institute, National Institutes of Health. Prior to his present position Dr. Bender was a member of the Department of Surgery at The Johns Hopkins Hospital. Thoracic and cardiovascular surgery are his principal clinical and research interests.

IT IS GENERALLY for the correction

agreed that the era of surgical intervention or amelioration

of congenital

heart defects be-

gan when Dr. Robert Gross performed the first successful closure This achievement set the stage of a patent ductus arteriosus.’ for subsequent

advances, beginning

of the aorta and repair

with resection

by direct end-to-end

of coarctation

reanastomosis

and

the use of systemic to pulmonary artery shunts to increase pulmonary blood flow in patients with cyanotic heart disease and

pulmonary valvotomy2

oligemia. led the

proaches to intracardiac 4

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Brock’s pioneering work on pulmonary way toward increasingly aggressive apdefects. This was soon followed by Bla-

lock and Hanlon’s atria1 septectomy3 and by Gross’ well technique for closure of atria1 septal defect.4 The early 1950s were characterized by a tremendous volume of work in developing techniques to allow intracardiac repair, including hypothermic circulatory arrest, cross circulation, and the cardiopulmonary bypass apparatus, first successfully employed by Gibbon5 and Warden et al6 The gradual development and improvement in the bypass apparatus led to increased patient protection during the performance of intracardiac repairs. More and more patients with acquired and congenital heart defects presented for operative intervention. Another major step occurred with the combination of cardiopulmonary bypass and profound hypothermic circulatory arrest. This led to increasingly aggressive approaches in neonates and small infants, whose defects were previously repaired with great difficulty or were palliated. In ensuing years there has been a great deal of progress and improvement in the surgical approach to congenital heart disease. There is now an improved understanding of the natural history of various congenital defects. Coupled with increased information about the results of surgical treatment, this knowledge has helped to establish criteria for the optimal timing of surgical intervention. Both simple and complex malformations have undergone further careful anatomical scrutiny, leading to more precise information regarding the relationships between morphology and function. Preoperative diagnosis has been greatly improved with the development and refinement of techniques of biplane cineangiography.72 * Multiple views taken with different orientations provide surgically important details of intracardiac and great vessel anatomy. The noninvasive technique of echocardiography has been established as a major tool of investigation and has provided accurate information on cardiac chamber dimension, patency of atria1 and ventricular septa, ventricular performance, and valvular abnormalities.g

NEONATAL

CIRCULATION

As the thrust in the management of congenital heart disease in children has progressed to evaluation, investigation, and intervention at increasingly younger ages, it is imperative that those who care for such children have some understanding of fetal circulation, neonatal circulation, and the profound changes in neonatal circulation that occur immediately following birth. The fetus receives oxygen and nutrition via the placental circulation. The foramen ovale allows blood to flow from the right atrium to the left atrium. The ductus arteriosus enables blood in the pulmonary circuit to enter the aorta and bypass the lungs. The ductus venosus shunts blood returning from the placenta in SEPTEMBER CPS

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the umbilical cord through the liver to the inferior vena cava. During delivery, asphyxia and the cold environment are strong respiratory stimuli. As a result of crying and vigorous respirations, the lungs expand and resistance to pulmonary blood flow falls rapidly. As the lung expands, it no longer compresses the pulmonary blood vessels, and there is a marked decrease in vasoconstriction of the pulmonary vessels. Clamping of the umbilical cord leads to a rise in systemic arterial resistance and prevents further blood return from the placenta. The inferior vena cava and right atria1 pressures fall, and the left atria1 pressure rises subsequent to the increase in systemic arterial resistance. The foramen ovale becomes functionally closed as the septum rimum closes the foramen and prevents interatrial shunting. P’ Many factors apparently influence closure of the ductus arteriosus following birth, but the major factor seems to be the contraction of the muscle within the ductus as it is exposed to increased oxygen tension in the arterial blood. The ability of ductal musculature to respond to increased oxygen tensions seems to be related to fetal age. More mature infants have a stronger response, and one that occurs at lower oxygen tension.ll Functional closure of the ductus arteriosus may begin soon after birth, but complete anatomical obliteration of the ductus does not occur until several months of age in the majority of infants. Initially there is persistent elevation of the pulmonary vascular resistance. There is a reduced volume of the pulmonary vascular bed due to the presence of persistent hyperplasia of the medial layer of the pulmonary arteries.12 Subsequent involutionary changes in the muscular media of the small pulmonary arteries over the first several weeks of life lead to a further fall in pulmonary artery pressure and resistance. In the newborn period, the hemoglobin level is usually 17 to 22 gm/dl, and by age 3 months the usual level is 10.5 to 11.5 gm/dl. This fall in hemoglobin level results in lower viscosity of the blood, and this contributes to the fall in pulmonary artery resistance. The hyperplastic medial layer of the pulmonary arteries regresses, and the pulmonary arterial walls become thinner. If there is an anatomical lesion that causes a left-to-right shunt, then the amount of shunting will increase remarkably as the pulmonary vascular resistance falls. For example, children with large ventricular septal defects and atrioventricular canal commonly do well until 6 to 10 weeks of age, when they present with pulmonary congestion and congestive heart failure due to the increasing left-to-right shunt. DUCTAL-DEPENDENT

LESIONS

IN THE NEONATE

Normally, pulmonary blood flow diminishes toward levels in the first week of life as the ductus arteriosus 6

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normal closes.

Neonates with pulmonary atresia or pulmonary atresia plus ventricular septal defect may present with severely diminished flow in the pulmonary circulation. Profound hypoxemia and acidosis may occur if there is insufficient pulmonary blood flow. The distal systemic circulation in neonates with severe preductal coarctation of the aorta or with interrupted aortic arch is dependent upon the patency of the ductus arteriosus, and they may experience circulatory collapse as the ductus closes. Effective temporary palliation, which allows time for improvement in the infants’ overall condition, may be achieved with the use of intravenous prostaglandin to keep open the ductus arterioin systemic or pulmonary blood flow sus. 13, l4 Improvement should occur, thereby allowing time for correction of metabolic abnormalities. As a result, the children come to the operating room in improved condition, and palliative or corrective procedures can then be carried out semielectively with a greater chance of success.15 INTRODUCTION

TO LESIONS

As the discussion continues, an attempt will be made to place the more commonly encountered congenital heart malformations with similar physiology into groups. It is hoped that this will facilitate an understanding of the physiologic burden imposed by the defects and the steps that are necessary to palliate or repair defects in the patients who fall into each group. The groups to be considered are those characterized by (1) increased pulmonary blood flow, (2) obstruction to flow, (3) decreased pulmonary blood flow, and (4) admixture.

INWEASEDPULMONARYBLOOD

FLOW

Communications between systemic and pulmonary circuits with predominant left-to-right shunts commonly cause congestive heart failure and increased pulmonary blood flow. Congestive heart failure is most commonly seen between 1 and 3 months of age as pulmonary vascular resistance falls and the left-to-right shunt increases, but it may be seen earlier in lesions such as aortopulmonary window and in newborns with a large patent ductus arteriosus. The noteworthy historical features in infancy typically are poor feeding, delayed growth and weight gain, and excessive sweating, especially with feeding. Physical examination usually reveals tachypnea, prolonged expiration, intercostal retraction, and inspiratory and expiratory wheezes or rales. There may be peripheral edema, seen most prominently in the eyelids and the dorsum of the feet and hands. Tachycardia and cardiomegaly are commonly noted. There may be an accentuated pulmonary closure sound, a gallop rhythm, SEPTEMBER CPS

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and a pulsus alternans. The extremities tend to be cool with weakly palpable pulses and peripheral mottling. The chest roentgenogram demonstrates an increased cardiothoracic ratio, which is due to ventricular dilatation and/or hyper-trophy. Also, signs of increased pulmonary blood flow are present, The electrocardiogram (ECG) characteristically shows tachycardia, P waves (suggesting atria1 hypertension), and prominent left ventricular forces. Right-sided failure may be identified by the presence of increased systemic venous pressure, enlargement and tenderness of the liver, edema, hydrothorax, and ascites. Patent Ductus Arteriosus The magnitude of the shunt through a patent ductus arteriosus is determined by the diameter of the ductus, the aortic and pulmonary artery pressures, and by the systemic and pulmonary vascular resistances. The systemic vascular resistance following birth is high and does not change significantly, so the major determinant that controls the amount of left-to-right shunt is the pulmonary vascular resistance, especially in the first few months of life as the pulmonary resistance falls. Left ventricular output is increased by the amount of blood shunted left to right through the lungs. A very large shunt will lead to left-sided heart failure with associated left atria1 hypertension and pulmonary congestion. An increase in sympathetic nervous system activity may lead to tachycardia and sweating. Persistent pulmonary hypertension due to a large left-to-right shunt may lead to increased pulmonary vascular resistance. True pulmonary vascular obstructive disease may result if a large shunt is allowed to persist for a prolonged period of time. In that case, the left-to-right shunt gradually diminishes, and eventually a rightto-left shunt will occur as pulmonary vascular resistance exceeds the systemic vascular resistance. Patients with a patent ductus arteriosus may present in four different manners. 1. Premature or full-term neonates with a large ductus develop excessive pulmonary blood flow and congestive heart failure. They are irritable and feed poorly. Many of the premature infants have associated respiratory distress syndrome and may require ventilatory assistance. Usually the diagnosis can be made on the basis of the clinical features, chest roentgenogram, and ECG. There is a hyperactive precordium and a murmur in the left second or third intercostal space. Classically the murmur has a continuous machinery quality, but it may be primarily systolic with prolongation into diastole. The pulses are bounding. The chest roentgenogram documents cardiomegaly and pulmonary plethora. The ECG may show evidence of left atria1 and left ventricular hypertrophy. The echocardiogram will help to confirm the diagnosis and to exclude aortopulmonary window or truncus arteriosus. 8 SEPTEMBER CPS

Medical management consists of digoxin, diuretics, and careful maintenance of adequate hematocrit and hemoglobin level, fluids, electrolytes, glucose, and nutrition requirements. Mechanical ventilatory support may be necessary. If the ductus fails to close with standard medical therapy and a large shunt with associated heart failure persists, the ductus must be closed. The proper timing of ductal closure and the method to be employed remain subjects of controversy and are under investigation. In recent years some infants have received indomethacin in an attempt to achieve nonoperative closure of a symptomatic ductus arteriosus.16 This treatment apparently works best in those infants younger than IO days of age and in less mature therapy should not be considered in ininfants.17 Indomethacin fants with renal dysfunction, bleeding, shock, necrotizing enterocolitis, or myocardial ischemia.i8 Operative closure of the ductus results in significant early benefits in the small preterm infant with a symptomatic patent ductus and a requirement for mechanical ventilation at one week of age. As compared to aggressive medical management, operation leads to a reduced duration of ventilator support and hospital stay, and an overall lower morbidity.lg It has been our practice to transport all patients to the operating room for closure of a patent ductus arteriosus. During transport, seriously ill neonates have to be monitored and ventilated with the utmost care. Very good results have been obtained elsewhere by operating on premature infants in newborn intensive care units,” but we have preferred to bring the patients to the operating room rather than vice versa. 2. In some children a large patent ductus will persist well past the newborn period, and there will be a significant left-to-right shunt with increased pulmonary blood flow. In most cases this is well tolerated, and congestive heart failure usually does not develop. In the past, cardiac catheterization was routinely performed in such patients to document the presence or absence of a patent ductus arteriosus and to quantify the size of the left-toright shunt. More recently it has been shown that two-dimensional echocardiography is an accurate noninvasive technique in the assessment of patent ductus arteriosus.21 Currently, if the clinical examination, chest roentgenogram, and echocardiogram are all consistent with patent ductus and do not suggest other lesions, then operative intervention may be undertaken without catheterization. Later closure of the ductus is not expected in patients in this group so it should be closed at a relatively early age. 3. The third clinical presentation is that of a relatively small ductus with a small shunt and a low risk of failure or eventual elevation of pulmonary vascular resistance. The major risk in this situation is the possible development of endarteritis. As SEPTEMBER CPS

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ductal closure is quite unlikely after age 4 or 5 years, the ductus should be closed operatively. 4. Occasionally an adult will present with aneurysm formation or calcification of the ductus. The usual surgical method of ligation or division of the ductus cannot be employed. In this circumstance, operative closure will require the utilization of cardiopulmonary bypass with suturing or patching of the ductus from within the pulmonary artery or the aorta. In good-risk patients with isolated g;tent ductus arteriosus the risk of operation is less than 0.5%. Complications of operations on the ductus arteriosus include bleeding, recurrent or residual patency of the ductus arteriosus, and injury to the recurrent laryngeal nerve. Aortopulmonary

Window

Failure of proper development of the aortic septum, which divides the truncus arteriosus into the aorta and pulmonary artery, may result in the formation of an aortopulmonary window. Typically there is a single communication, located just above the aortic valve, with a diameter varying from several millimeters to a centimeter or more. The relationship of the right pulmonary artery to the window is variable, and the right pulmonary artery may arise from the aorta or at the site of the window.23 The physiologic effects of this defect are similar to those of a patent ductus arteriosus. The size of the defect and the ratio of the systemic and pulmonary vascular resistances determine the amount of left-to-right shunting. As the pulmonary vascular resistance falls following birth there is increased shunting, which results in the early onset of significant congestive heart failure. The physical signs are virtually indistinguishable from those of patients with a patent ductus arteriosus except that the murmur is best heard lower and more medially. Chest roentgenograms document cardiomegaly and increased pulmonary blood flow. The ECG demonstrates prominent left-sided forces. Usually this defect leads to profound heart failure in infancy, and operative intervention is required as soon as the diagnosis is established. Multiple surgical approaches to the repair of aortopulmonary window have been utilized in the past. These include ligation, clamping and division of the window, division and suture of the aorta and pulmonary artery during caval occlusion or during cardiopulmonarzbbypass, transaortic repair utilizing cardiopulmonary bypass, or closure of the defect through an anterior incision in the front wall of the communication and repair with a patch.25 We have preferred the latter approach, as it provides excellent visualization of the communication between aorta and pulmonary artery and the relationship between the communication and the origin of the right pulmonary artery. Currently, operative correction is most often carried out on cardiopulmo10 SEPTEMBER CPS

nary bypass or under Operative mortality 25%. If correction is opment of pulmonary long-term outlook is sual. Ventricular

deep hypothermia with circulatory arrest. in various series has ranged from 0% to successfully undertaken prior to the develvascular obstructive disease, then the excellent and late complications are unu-

Septal Defects

Clinical assessment of ventricular septal defect includes an analysis of its size and position, of the hemodynamics of shunting, and the status of the pulmonary vascular resistance. The most common type of ventricular septal defect is the perimembranous or infracristal defect, which is found in about 80% of cases. It lies in the outflow tract of the left ventricle adjacent to the aortic valve. Outlet defects are located in the right ventricular outflow tract beneath the pulmonary valve. Isolated defects located posterior and inferior to the perimembranous location are termed posterior defects. Defects in the muscular septum may be single or multiple and most frequently occur at the apex. The magnitude of the shunt through a ventricular septal defect depends on the size of the defect and the ratio of pulmonary to systemic vascular resistance. In patients with a small or medium-sized defect, the major determinant of shunting is the size of the defect. With a very large or nonrestrictive defect, the relative resistance of the pulmonary and systemic circuits determines the magnitude of the shunt. At birth there is a relatively high pulmonary vascular resistance, so there is only a small left-to-right shunt, even in the presence of a large defect. During the first several months of life, with the gradual decline in pulmonary vascular resistance, the amount of shunting increases markedly. Left ventricular failure may occur as a result of the tremendously increased pulmonary blood flow. This is manifested by enlargement and hypertrophy of the left atrium and ventricle, tachypnea, sweating, poor feeding, and delayed growth and development. Often the large shunt and congestive heart failure will persist, and the pulmonary vascular resistance will remain stable. However, in some patients, pulmonary vascular obstructive disease develops within the first year of life. This leads to diminished shunting and alleviation of congestive heart failure. If this condition progresses there will eventually be right-to-left shunting across the defect, and the patient’s condition will become inoperable by reason of fixed pulmonary vascular obstruction. Symptomatic infants usually present at 6 to 10 weeks of age with severe congestive heart failure, failure to thrive, and/or chest infections. They are treated with digoxin and diuretics in an attempt to control heart failure. Afterload reduction is theoretically attractive, but this has not been performed in conSEPTEMBER CPS

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trolled clinical trials. Short-term studies with intravenous hydralazine have shown that systemic flow may be increased without change in pulmonary flow, resulting in a decrease in left-toright shunting. Further trials of hydralazine in symptomatic infants with large left-to-right shunts may be indicated.26 Operative intervention is undertaken in infants with a large left-to-right shunt and profound congestive heart failure despite maximum medical management. Without closure of the defect, these children face the hazards of repeated pulmonary infections, poor growth and weight gain, and the possibility of developing advanced pulmonary vascular obstructive disease. The preferred operative technique is early primary closure rather than banding of the pulmonary artery.27 Symptomatic infants with multiple defects or with an apical ventricular septal defect sometimes still undergo pulmonary artery banding due to the difficulty in obtaining satisfactory closure in infancy and because of the necessity for a left ventriculotomy, respectively. Some children with a somewhat smaller ventricular septal defect have a significant left-to-right shunt but do not develop congestive heart failure, and some of those who do develop failure respond well to medical management. These children must be followed closely, paying special attention to signs of increased pulmonary resistance. These children are operated on electively, usually between ages 2 and 3 years, or earlier if increased pulmonary vascular resistance develops. Severely elevated pulmonary arteriolar resistance of approximately 10 unit&q m is usually considered to signify an inoperable condition. Patients with a small or only moderate-sized ventricular septal defect and normal pulmonary vascular resistance may be followed because of the natural tendency of these defects to become smaller or to close spontaneously. If the patient develops an episode of endocarditis, strong consideration should be given to closing the defect as that lowers the risk of subsequent episodes of endocarditis. Approximately 5% of patients with ventricular septal defect will experience aortic valvular insufficiency. Usually the right or noncoronary cusp protrudes into the ventricular septal defect. Valvular insufficiency is usually progressive, and operative closure of the ventricular septal defect and repair of the aortic valve, if necessary, are indicated to prevent progressive regurgitation. In children older than 3 months, repair of a ventricular septal defect is usually carried out under conventional hypothermic cardiopulmonary bypass and cardioplegia. In younger and smaller children the defect is usually repaired with deep hypothermia and circulatory arrest. Commonly, the repair of a ventricular septal defect is undertaken through the right atrium. This approach affords excellent exposure in the majority of 12

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cases, and it obviates the necessity for a right ventriculotomy with its associated adverse effect on right ventricular function. If exposure is limited and the defect or defects cannot be clearly visualized, a right ventriculotomy may become necessary. In cases of multiple ventricular septal defects or an apical septal defect, a left ventriculotomy with patch closure may be necessary.2s Repair of an isolated uncomplicated ventricular septal defect in good-risk patients should be accomplished with a mortality rate of approximately 5% or less.” Primary repair of ventricular septal defect in infancy has a lower mortality and morbidity than initial pulmonary artery banding followed by subsequent closure of the defect and debanding.27, ’ The risk of operation is even less, approximately 1% to 2%, in children older than 2 years with normal or only slightly increased pulmonary vascular resistance.31 There are limited data on longer-term evaluation of patients following closure of a ventricular septal defect with a moderate to large left-to-right shunt. Most patients have normal growth, development, and activity, but there may be residual increased left ventricular end-diastolic volume, left ventricular wall mass, depressed left ventricular ejection fraction,32 or abnormal reseptal desponse to upright exercise.33 Closure of a ventricular fect in infancy may be associated with better left ventricular function, a smaller left ventricular end-diastolic volume, and less left ventricular mass, than operation later in childhood.34V 35 Complex cardiac defects associated with high pulmonary flow due to a large left-to-right shunt sometimes result in congestive heart failure in infancy. These lesions include high-flow tricuspid atresia, univentricular heart, double-outlet right ventricle, corrected transposition of the great arteries with associated ventricular septal defect, and transposition of the great arteries with associated ventricular septal defect. If congestive heart failure is not easily controlled with anticongestive measures, palliative pulmonary artery banding is performed. Complications of pulmonary artery banding are multiple. The band may be placed too loosely or too tightly. Too tight a placement of a band will result in unsatisfactory pulmonary blood flow, and a band that is too loose will result in residual pulmonary hypertension and pulmonary vascular obstructive disease. The band may cut through the pulmonary artery either acutely or gradually. The band may migrate distally toward the bifurcation of the pulmonary arteries, resulting in distortion or narrowing of one or both pulmonary arteries, which may complicate subsequent attempts at complete repair. At the time of pulmonary artery debanding it may be necessary to reconstruct the pulmonary artery. Sometimes removal of the band is all that is necessary. In other circumstances a pulmonary angioplasty can be carried out using a longitudinal pulSEPTEMBER CPS

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monary artery incision with transverse closure, or a patch angioplasty of the pulmonary artery, or resection of the banded segment of pulmonary artery and repair with end-to-end anastomosis. Atrioventricular

Septal

Defects

The spectrum of cardiac malformations included under the general heading of atrioventricular septal defects includes varying degrees of maldevelopment of the atrioventricular valves, atria1 septum, and the inflow portion of the ventricular septum. In the partial form of this defect there is usually a large ostium primum atria1 septal defect. There is typically a cleft in the midportion of the anterior leaflet of the mitral valve. In some patients there will be a coexisting ventricular septal defect. The complete form of the atrioventricular septal defect includes an ostium primum type of atria1 septal defect and a ventricular septal defect, in conjunction with a single atrioventricular valve. Rastelli et al. 36 classified these defects into types A, B, and C, based on the variable anatomy and relationships between the anterior bridging leaflet, chordae, and the underlying ventricular septum. There may be domination by the right ventricle or left ventricle, but commonly there is bilateral enlargement of the right and left ventricles and a central position of the common atrioventricular valve. In the intermediate form of the atrioventricular septal defect there is an ostium primum-type atria1 septal defect with fusion of the anterior and posterior bridging leaflets on top of the ventricular septum. The mitral and tricuspid portions of the atrioventricular valve are still unified, and there are not separate left and right atrioventricular valves. The symptomatology associated with atrioventricular septal defects depends on the magnitude and direction of the associated shunt, which is determined by the size of the atria1 defect, the size of a ventricular septal defect, and the ratio of pulmonary to systemic vascular resistance. In the presence of elevated pulmonary vascular resistance there may be only a small left-toright shunt. Consequently, there will be no symptoms of congestive heart failure. If the pulmonary vascular resistance is greatly elevated there may be cyanosis due to right-to-left shunting. Definitive diagnosis is obtained by cardiac catheterization and angiocardiography. An alternative technique utilized more recently is two-dimensional echoeardiography. The partial atrioventricular septal defect occurs approximately one fourth as frequently as the secundum-type atria1 defect. As a general rule, these patients have more severe symptoms than patients with secundum atria1 septal defect, and the symptoms occur at an earlier age. Most patients have mild to moderate mitral valve regurgitation. Ordinarily, operation is undertaken electively during the preschool years, unless signif14 SEPTEMBER CPS

icant growth failure or heart failure mandate earlier operation. A small proportion of these patients present with severe symptoms in infancy and may require urgent operation at an early age. Operative repair of a partial atrioventricular septal defect is usually safe and straightforward. If significant mitral regurgitation is present, the edges of the mitral cleft are reapproximated with fine interrupted sutures, and the primum atria1 septal defect is closed with a patch of pericardium or dacron. Extreme care must be taken not to injure the conduction system, and some authors recommend placing the patch so as to end up with the coronary sinus on the left atria1 side of the patch.37 We leave the coronary sinus within the right atrium. The patch is sutured to the crest of the ventricular septum or into the mitral valve anulus in the region of the conduction system. Heart block as a complication of operation occurs in less than 1% of the patients. Operative mortality is approximately 5% or less in those patients without major associated anomalies.38 Late follow-up data document an actuarial survival of 94%. Most patients are asymptomatic, but subsequent mitral valve repair or replacement due to progressive mitral regurgitation is necessary in the late postoperative period in approximately 5% of patients.3g Children with complete atrioventricular septal defects typically present in moderate to severe congestive heart failure. Symptoms usually occur early in infancy as the hematocrit falls and the pulmonary resistance drops. This leads to a huge leftto-right shunt, which occurs both in systole and diastole. Severe cardiac failure results, manifested by tachypnea, sweating, poor feeding, delayed growth, and repeated respiratory infections. The primary hemodynamic abnormality that causes heart failure and high mortality in infants appears to be a large left-toright shunt at both the ventricular and the atria1 leve14’ Patients not operated on have a mortality of 65% by age 12 months and 96% by age 5 years.41 If severe elevation of pulmonary arteriolar resistance has developed, operation is contraindicated. Otherwise, operative intervention is recommended in all infants presenting with intractable heart failure. Pulmonary artery banding gives unpredictable results, and it has had a high operative mortality.42 More recently, complete repair in infancy using profound hypothermia and circulatory arrest has provided good results with an operative mortality as low as 8% and infrequent late deatbs4’ Repair may be undertaken with either a single Dacron patch to close both the atria1 and the ventricular defects or, with two separate patches. Integrity of the valves is accomplished by resuspension of the right- and left-sided portions of the atrioventricular valve to the patch (Fig 1). In the University of Alabama series, the major predictive risk factors for operation included increasing severity of the incompetence of the atrioventricular valve, poor preoperative functional class, and the presence of an SEPTEMBER CPS

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Fig 1.-A, operation for complete atrioventricular canal. A right atriotomy has been performed. Interrupted sutures approximate the anterior and posterior components of the anterior leaflet of the mitral valve. Broken line indicates line of incision in posterior common leaflet. VSD, ventricular septal defect; WC, inferior vena cava; WV, right pulmonary veins; Ao, aorta; SVC, superior vena cava; WA, right pulmonary artery. B, the inferior portion of a single patch is sutured to the right side of the interventricular septum. All sutures are placed prior to lowering the patch into position. C, the mitral and tricuspid margins of the divided or incised anterior and posterior common leaflets are sutured to the patch as necessary with interrupted horizontal mattress sutures corresponding to the plane of the normal mitral or tricuspid annulus. D, the repair is completed by suturing the most cephalad portion of the patch to the rim of the atrial septum. (From McMullan M.H., et al.: Surgical treatment of complete atrioventricular canal. Surgery 72:905, 1972. Used by permission of the C.V. Mosby Company.)

accessory valve orifice.38 In the experience at this institution, the results of operation have been related to the complexity of the repair, the pulmonary vascular resistance, and the preoperative nutritional status of the patient. Late death following complete repair of atrioventricular septal defect is uncommon, and late reoperation for residual or recurrent mitral valve incompetence is unusual. Complete heart block results in approximately 1% of the patients. Secundum Atria1 Septal Defects

Secundum atria1 septal defects are one of the most common congenital heart lesions. They are usually not associated with other intracardiac defects, but are sometimes associated with mitral valve stenosis or prolapse. The defect in the septum may consist of one large opening or several small openings. The de16 SEPTEMBER CPS

feet results from failure of the septum secundum to cover completely the foramen secundum. The size of the defect may vary from less than 1 cm in diameter to virtual absence of the interatria1 septum. Usually atria1 septal defects are so large that they do not restrict the flow of blood across them, and the relative resistance to filling of the right and left ventricles determines the amount and direction of the shunt. The left ventricle pumps into the high-resistance systemic circulation, so it is thicker and less distensible than the right ventricle, which pumps into the low-resistance pulmonary circulation. The pressures in the right and left atria are virtually the same in the presence of a large defect, and the right ventricle is filled more easily than the left. Consequently, there is usually a large left-to-right shunt. Commonly, pulmonary blood flow is two to four times normal, but the pulmonary artery pressure is almost always normal. There may be a mild pressure gradient across the pulmonary valve as a result of the large pulmonary flow passing through a normal-sized valve. Pulmonary vascular obstructive disease is quite rare in children, but is found occasionally in adult patients with a long-standing shunt due to an atria1 septal defect. The great majority of patients with secundum atria1 septal defect are asymptomatic, and the defect is usually diagnosed on the basis of typical physical findings in an asymptomatic child after age 2 years. Symptoms, if present, usually consist of mild shortness of breath or dyspnea on exertion. Frank congestive heart failure occasionally occurs. Rarely, infants will present with severe congestive heart failure and require early operative closure of the defects.43 Operative intervention is usually recommended if cardiac catheterization documents an increase in pulmonary blood flow which is at least 1% times greater than the systemic blood flow. Previous natural history studies have suggested that patients with atria1 septal defect and significant left-to-right shunt slowly develop an increase in pulmonary resistance with concomitant development of symptoms. With increasing development of pulmonary resistance a right-to-left shunt may appear. For this reason significant atria1 septal defects should be closed electively prior to the development of pulmonary hypertension. Occasionally a patient with atria1 septal defect will present in the fourth to sixth decade of life. Typical findings may include dyspnea, intermittent cyanosis, supraventricular arrhythmias, and polycythemia. At cardiac catheterization, pulmonary hypertension, increased pulmonary vascular resistance, and bidirectional shunting are frequently found. A very careful study is necessary to determine whether the net shunt is left to right or right to left. If the net shunt is left to right, patients generally do well and achieve significant clinical and hemodynamic benefit following closure of the defect.& SEPTEMBER CPS

17

Currently, operative correction of atria1 septal defect is performed on cardiopulmonary bypass. The median sternotomy approach is favored, although the procedure can also be undertaken through a right thoracotomy. An alternative approach is a submammary incision with elevation of flaps and midline sternotomy.45 Usually the defect is closed with a pericardial or prosthetic material; small defects can be occasionally closed by direct suture without tension. In good-risk patients, operative mortality is 1% to 2%. In symptomatic infants or those presenting in the older age group, the presence of congestive heart failure and increased pulmonary arteriolar resistance increase the risk of operation. Postoperative studies in children undergoing closure of atria1 septal defect between ages 2 and 17 years showed persistent right ventricular enlargement by M-mode echocardiography in 80% of the patients. The functional significance of this is not known.46 Significant arrhythmias and sinus node dysfunction may occur postoperatively as a result of operative trauma to the conduction system. However, careful preoperative assessment of patients with noninvasive and invasive electrophysiologic techniques has documented abnormal corrected sinus node recovery time and atrioventricular nodal dysfunction in a significant proportion of patients.47 As a general rule, postoperative rhythm disturbances are transitory and can be managed with digoxin and other antiarrhythmic medication. Patients with significant preoperative arrhythmias often have no change in arrhythmia status following operation. Truncus Arteriosus Truncus arteriosus consists of a single arterial trunk arising from both ventricles by way of a single semilunar valve, a high ventricular septal defect, and pulmonary arteries originating from the truncus. Patients are categorized into various types depending on the origin of the pulmonary artery or arteries from the truncus.48 Patients occasionally survive to adulthood without operation, but this is unusual, and survival beyond the first year of life is uncommon. Neonates with this condition generally become severely ill with congestive heart failure as the pulmonary vascular resistance falls and the left-to-right shunt increases. The median age at death varies from several weeks to 6 months4’ Death after infancy may be due to congestive heart failure, but more frequently results from the complications of severe pulmonary vascular disease. Preoperative investigation involves cardiac catheterization with measurement of the pressure and oxygen content in both pulmonary arteries. Angiocardiography defines the great artery anatomy and assesses the truncal valve. Injection into the truncal root is utilized to assess possible truncal valve incompetence. Cardiac failure is managed with intensive digoxin and di18

SEPTEMBER

CPS

uretic therapy. Neonates in intractable congestive heart failure are operated on regardless of age or size. In recent years pulmonary artery banding has not been performed due to the high mortality and poor results with this technique,50 and in any case, pulmonary artery banding may not prove effective in preventing the development of severe pulmonary vascular disease. Severe distortion of one or both pulmonary arteries by banding may seriously compromise subsequent operative options. Most centers have abandoned pulmonary artery bandin and have performed total correction in symptomatic children. 55 Operative outcome depends primarily on the pulmonary vascular resistance. If the pulmonary vascular resistance exceeds 10 units sq m, the prognosis is better with medical treatment than with operation. The essential steps of repair of truncus arteriosus include detachment of the main pulmonary artery or the individual pulmonary arteries from the truncus and repair of the aorta with direct suture or a patch, closure of the ventricular septal defect, and connection of the right ventricle to the pulmonary artery or arteries with an extracardiac conduit (Fig 2). Aortic homograft conduits are preferred and are used when available. Heterograft conduits containing a bioprosthetic valve are used if homografts are not available. In general, it is possible to insert a larger homograft than a heterograft, and late obstruction is not commonly seen. There have been a few successful cases of early repair using a nonvalved conduit. Fairly

commonly

regurgitation. the truncal

there will be mild to moderate

Usually

this is best handled

valve in view

of incompletely

sults of valve replacement tally significant

dication

truncal

for replacement approximately

commonly

satisfactory

However,

valve

of

late re-

hemodynami-

valve stenosis or regurgitation

is an in-

of the valve.53

The usual extracardiac

small,

in children.

truncal

by conservation

conduit

placed in an infant

12 to 16 mm in diameter.

is quite

This conduit

must be replaced after three to five years because of

growth of the child, and sometimes because of progressive stenosis of the conduit. Fortunately, conduit replacement can be carried out at a risk of approximately 5%. Operative mortality for repair of this defect has ranged from 10% to 30%. Poor preoperative

condition

and pulmonary

vascu-

lar obstructive disease are two of the major determinants of outcome.51 Late mortality seems to be related primarily to the degree of pulmonary vascular obstructive disease present at the time of the initial

operation.54

OBSTRUCTIVE LESIONS The major obstructive

obstruction

congenital

to left ventricular

cardiovascular

output

lesions cause

(coarctation

of the aorta,

SEPTEMBER CPS

19

Fig 2.-Operation for Type I truncus arteriosus. A, an incision is made in the truncus at the base of the insertion of the pulmonary arteries. B, after detaching the pulmonary artery, the defect in the aorta is closed by sutures (a), or with a patch (b/. C, a vertical right ventriculotomy is performed. D, the ventricular septal defect is closed with a patch to direct the left ventricular flow to the aorta. E, the extracardiac valved conduit is anastomosed to the pulmonary artery (a and bl. F, the proximal anastomosis (with the ventricle) is made as wide as possible. Aortic homografts are preferred, but when these are not available, heterograft conduits are employed, as shown. G, the completed rep lair. (From de Leval M.: Persistent truncus arteriosus, in Stark J., de Leval M. (eds.): : Surgery for Congenital Heart Defects. New York, Grune & Stratton, Inc., 1983, pp. 41 7-425. Used by permission.)

interrupted aortic arch, left ventricular outflow tract obstruction), obstruction to left ventricular inflow (mitral stenosis, car triatriatum), or obstruction to the right ventricular outflow tract (pulmonary valve stenosis, right ventricular infundibular stenosis, double-chambered right ventricle). The clinical features of the various lesions all derive from the difficulty in forcing blood past an obstructing point in the cardiovascular circuit. Coarctation of the Aorta Coarctation of the aorta may occur as a long tubular narrowing proximal to the ductus arteriosus, or as a discrete obstruction in a juxtaductal position. Sometimes both obstructive components are present. Coarctation may occur as an isolated lesion or in association with a patent ductus arteriosus, ventricular septal defect, bicuspid aortic valve, or other lesions. Patients with coarctation of the aorta present either as asymptomatic older children or with severe congestive heart failure in infancy. Occasionally an older child may complain of 20 SEPTEMBER CPS

exercise-related tension in the ished pressure femoral pulses. the left sternal

pain in the legs. The typical features are hyperright (and sometimes the left) arm and diminin the legs associated with absent or decreased

There is usually

a short systolic murmur

border with radiation

along

to the neck and back. Typ-

ically there is a loud systolic murmur in the left paraspinal region, and a continuous murmur may be heard over the left chest if there are well-developed collaterals. The symptomatic neonate presents with heart failure and failure to thrive. There is a history of irritability, poor feeding, and breathlessness. The babies are tachypneic and dyspneic and have an ashen color. There is a systolic murmur along the left upper sternal border, with radiation to the back. There is hypertension

in one or both arms and diminished

pulses and pressure

in the legs. Frequently

there is severe congestive heart failure

and low cardiac output

due to the systemic afterload

the obstructing fusion

coarctation.

of the lower body is severely

profound

metabolic

caused by

If the ductus arteriosus

closes, per-

compromised,

resulting

in

acidosis.

In those neonates whose distal aortic perfusion is dependent on the ductus arteriosus, prostaglandin El is given intrave-

nously to maintain patency of the ductus arteriosus or to restore patency if the ductus closes. Given as a resuscitative measure, this allows catheterization to be carried out with greater ease, safety, and thoroughness.

be performed

lay for improvement

restoration erative

Critically

operation

basis but allowing

in the patient’s

of the distal perfusion.

intervention

paratively

In most instances

still on an urgent

overall

may then

sufficient

condition

General anesthesia

can then be carried

de-

following

and op-

out in a patient

in com-

good condition.15 ill infants

should be operated

with

profound

congestive

on as soon as their condition

heart

failure

has been maxi-

mally stabilized with the prostaglandin infusion. Older, asymptomatic patients are operated on electively in view of the poor long-term prognosis of untreated patients with hemodynami-

tally significant coarctation. The appropriate timing of elective surgical intervention in older children with coarctation of the aorta is influenced by concerns regarding growth and long-term fate of the anastomotic site. One long-term

study of patients

during adolescence cular complications

or young adulthood showed late cardiovasin a significant proportion of cases.55 An-

other report showed a lower incidence

sion in those patients than in those operated

who underwent of postoperative

who were operated

operation hyperten-

on before age 5 years

on later.56 These data indicate

that elec-

tive repair of coarctation of the aorta early in childhood might prove to be an important factor in preventing late hypertension, left ventricular hypertrophy and dysfunction, and endarteritis. Blalock and Park57 reported an experimental operation for SEPTEMBER CPS

21

coarctation of the aorta. Their procedure involved anastomosis of the left subclavian artery to the aorta distal to the coarctation. Coarctation of the aorta was first repaired bg, ;zsection of the involved area and end-to-end reanastomosis. For many years this technique was used exclusively. In recent years there has been great interest in the development of other methods of repair in infants due to the relatively high rate of recurrence following end-to-end repair.60-62 The E;osthetic patch aortoplasty63 and subclavian artery flap repair have been used more frequently over the past few years as increasing experience with these procedures and good long-term results have accumulated (Fig 3.)65P66 In one report a more effective relief of aortic obstruction in infants was found when the repair was carried out with prosthetic patch aortoplasty rather than resection and end-to-end anastomosis.67 Unfortunately, some patients who undergo prosthetic patch graft aortoplasty may later have aneurysm formation in the aortic wall opposite the patch.68 Fig 3.-Subclavian flap repair of coarctation in a neonate. A, through a left lateral thoracotomy the mediastinal pleura is dissected and retracted, the ductus arteriosus and subclavian artery are ligated, and aortic clamps are applied proximally and distally. The aorta is incised below the level of the ductus, and the along the lateral wall of the subclavian artery. B, the coarctaincision is carried helf is carefully



22 SEPTEMBER CPS

coarctation. (From Moulton A.L., vian repair of coarctation of the nates. Realization of growth Thorac. Cardiovasc. Surg. 87:220, ..-- L.. L, ..^.-:^^:^^ ^‘a.^

et al.: Subclaaorta in neopotential? J. 1984. Used rr-----.. \

Recent reports suggest that the subclavian flap procedure may result in a low incidence of persistent stenosis or recoarctation.66. 6g Waldhausen et al. 7o have reported nine infants younger than 1 year who underwent the subclavian flap procedure and were followed up for a mean of 17.8 months without evidence of significant residual or recurrent obstruction. The postoperative catheterization and angiography results of Hamilton and co-workers66 in five children who underwent subclavian artery flap aortoplasty repair at less than 6 months of age and who were reinvestigated three to seven years following repair showed absence of a pressure gradient across the reconstructed area, and aortograms documented that the reconstructed area had grown in girth and had attained adequate caliber for the age of the child. Erath et a1.71 performed subclavian artery flap aortoplasty in normal puppies that were restudied 12 months later. The flap segment grew 74% in length and over 100% in width.71 The left subclavian flap aortoplasty is currently our technique of choice for repair of coarctation of the aorta in symptomatic infants. It is a relatively simple operation, and the morbidity and mortality rates are at least as good as those with other types of repair. Excellent short- and medium-term results have been obtained by us and others, and it is hoped that this procedure will lead to a lower incidence of recurrent coarctation over more prolonged follow-up. Thus far only 12% of our infant patients who underwent coarctation repair utilizing the subclavian artery flap technique have required reoperation for recurrent coarctation. This is in contrast to a 35% recurrence rate in infants previously repaired with the end-to-end technique. Usually no morbidity results from sacrifice of the left subclavian artery in small children. Reports of left arm ischemia followirrg sacrifice of the left subclavian artery are extremely rare. Other reports have documented the absence of left upper limb ischemia of children surviving flap repair of coarctation of the aorta, but some patients did develop significant shortening of the left upper arm.73 Another report has documented that transection of the left subclavian artery in children undergoing various procedures results in significantly decreased left arm blood pressure. However, exercise resulted in a significant increase in the brachial artery pressure in both arms. By one week following operation there was no significant difference in temperature of the two limbs, but there was a significant decrease in limb growth on the side operated on.74 The maximum safe age for sacrifice of the subclavian artery is not known. The subclavian artery flap aortoplasty is not appropriate for all patients with coarctation of the aorta. If the subclavian artery is quite small the resulting flap may not have sufficient diameter to relieve the obstruction. In addition, if the coarctaSEPTEMBER

CPS 23

tion is located quite distally on the descending thoracic aorta then the subclavian flap may not have sufficient length. In that circumstance either the subclavian flap may be lengthened with a synthetic patch or the repair could be carried out entirely with a synthetic patch. If the coarctation occurs between the left carotid and left subclavian vessels then a reversed subclavian flap angioplasty may be attempted75 or a synthetic patch may be inserted. In this circumstance the subclavian artery may not be of adequate size. It is not located proximal to the obstruction, therefore it has not been exposed to the proximal aortic hypertension, and it has probably not functioned as an important collateral as it does in the case of the usually situated juxtaductal coarctation. Two important technical factors deserve mention. The subclavian flap and the aortotomy should be brought down well distal to the point of maximal narrowing. In this way the suture line will not be carried transversely across the aorta at the point of the maximal narrowing. In addition, the posterior shelf should be resected as completely as possible to relieve the obstruction acutely and to help prevent recurrent obstruction. The most devastating complication of coarctation repair is spinal cord ischemia and paraplegia. Maintenance of an adequate distal aortic pressure may be important in preventing spinal cord ischemia during aortic clamping.76 It is important to assess the collateral arteries preoperatively and in the operating room to ensure adequate flow in the distal aorta. Distal aortic perfusion can be improved by utilizing a temporary shunt from the left ventricular apex, ascending aorta, or left subclavian artery to the descending aorta. Alternatively, the patient could be placed on cardiopulmonary bypass in order to supply distal aortic perfusion via the femoral artery or distal thoracic aorta. These adjunctive maneuvers are only rarely necessary, as collateral flow is almost always sufficient to achieve adequate perfusion of the distal aorta during the repair. Another risk factor in the development of spinal cord ischemia is bleeding following the removal of the aortic clamps. Significant hypotension may occur due to hypovolemia and reactive hyperemia of the lower body, and there is a washout of acid metabolites from the lower body once distal perfusion is restored. It is important to control the blood loss with digital pressure and to restore the circulating blood volume and correct the pH prior to reapplication of the aortic clamps. The appropriate management of patients with coarctation and ventricular septal defect remains controversial. The majority of infants with coarctation and a small ventricular septal defect can be managed with initial repair of the coarctation. Usually there is an adequate response to the operation and continued medical management. The ventricular septal defect can be repaired on an elective basis subsequently if a large left-to-right 24 SEPTEMBER CPS

shunt persists. However, if there is a large ventricular septal defect with a large left-to-right shunt, we believe pulmonary artery banding should be carried out at the same time as the coarctation repair. Those children who have a large persistent shunt following coarctation repair alone remain in severe congestive heart failure and are poor candidates for subsequent operation. Usually these quite sick children respond dramatically to early coarctation repair and pulmonary artery banding, and they can be operated on again electively at age 3 to 6 months when they are in good condition. At that time they undergo pulmonary artery debanding and ventricular septal defect repair with excellent results.77 If there are multiple ventricular septal defects or a large apical muscular defect then strong consideration should be given to pulmonary artery banding at the time of coarctation repair, as repair of these defects in young children. is often difficult and may well require a left ventriculotomy tl, achieve a satisfactory closure. Pulmonary artery banding should also be strongly considered as an accompanying procedure in patients with associated single ventricle or other complex lesions that require long-term palliation. Paradoxical hypertension, which may occur following operation 78 should be controlled with an intravenous infusion of sodium nitroprusside. Additional control can be obtained with propranolol. Occasionally patients will experience mild abdominal pain and prolonged ileus. In recent years, with better control of postoperative hypertension, mesenteric vasculitis associated with severe intestinal ischemia has become quite rare.

Interruption

of the Aortic Arch Interrupted aortic arch is a severe cardiovascular abnormality that usually causes severe congestive heart failure in the newborn. The three anatomical variants of this defect were classified by Celoria and Patton in 1959. 7g In the type A defect, the interruption of the aortic arch is distal to the left subclavian artery. In the type B defect, the interruption is between the left carotid and left subclavian artery, and in the type C, the interruption is between the innominate or right carotid artery and the left carotid artery. A ventricular septal defect is commonly associated with all types of interrupted aortic arch. There may be other associated defects, such as aortopulmonary window, or left ventricular outflow tract obstruction. Some of these neonates will also have DiGeorge’s syndrome, or absence of the parathyroids, which may cause profound hypocalcemia. Repeated determinations of the serum calcium level must be performed along with the administration of supplemental calcium as necessary. Patients with interruption of the aortic arch usually present shortly after birth with severe symptoms. The clinical manifestations are variable and depend on the presence or absence of associated defects, the pulmonary vascular resistance, and the size of the shunt through the ductus arteriosus. Lower body perSEPTEMBER CPS 25

fusion is dependent on reversal of flow through the ductus arteriosus, and restriction of flow leads to hypoperfusion of the legs, oliguria, and metabolic acidosis. The diagnosis is established with cardiac catheterization, angiocardiography, and echocardiography. Patients are treated with prostaglandin El to maintain patency of the ductus arteriosus in an attempt to provide adequate blood flow to the lower portions of the body. The metabolic status is corrected as much as possible, and the child is stabilized and prepared for operative intervention without delay. In recent years, there has been increasing success in total correction of this anomaly, under deep hypothermia and circulatory arrest. Repair of the type A interruption can be carried out by dividing the ductus arteriosus from the pulmonary artery, closing the defect in the pulmonary artery, resecting the ductus arteriosus from the descending aorta, extensively mobilizing the descending aorta, and directly anastomosing the descending aorta to the transverse aorta. Rarely, it is not possible to mobilize the aorta sufficiently for a direct anastomosis. In this situation, continuity may be obtained by turning the left subclavian artery down onto the descending aorta or by using a prosthetic interposition graft. The ventricular septal defect may be closed with a patch. If the ventricular septal defect is not going to be closed in a type A interruption the aortic repair may be carried out through a left thoracotomy. The pulmonary artery may be banded as an associated procedure. Complete repair using profound hypothermia and total circulatory arrest is the procedure of choice for types A, B, and C. If there is significant left ventricular outflow tract obstruction, the operation is likely to be unsuccessful. Usually the left ventricular outflow tract obstruction cannot be repaired in the neonate, and some form of palliative operation has to be undertaken. Litwin et al.*’ have suggested interposition of a prosthetic graft between the proximal main pulmonary artery and the upper descending aorta. Both anastomoses are carried out end to side. The ductus arteriosus is ligated, and the main pulmonary artery is banded distal to the graft and proximal to the pulmonary artery bifurcation. Left Ventricular Outflow Tract Obstruction Left ventricular outflow tract obstruction may be due to narrowing of the subvalvar region, a malformed aortic valve, a small aortic anulus, or supravalvar stenosis. These lesions may exist singly or in combination. Subaortic stenosis may occur as a discrete membrane located immediately below the aortic valve with an otherwise normal left ventricular outflow tract. The lesion in discrete membraneous subaortic stenosis consists of a diaphragm-like fibrous ring encircling the left ventricular outflow tract immediately beneath the aortic valve. A mild degree of aortic valve insufficiency is commonly observed with this con26 SEPTEMBER CPS

dition. Operative repair consists of excision of the obstructing membrane or fibrous ridge beneath the aortic valve. The fibromuscular type of subaortic stenosis is associated with hypertrophy of the musculature of the left ventricular outflow tract and narrowing of the outflow tract, which may form a fibromuscular tunnel.” Operative correction of a tunnel subaortic stenosis may be extremely complicated due to the difficulty in relieving obstruction in a long, narrow tunnel. It may be necessary to replace the aortic valve, enlarge the aortic anulus and proximal aorta, and enlarge the left ventricular outflow tract. Various techni ues have been devised for treatment of this condition.8253 Alternatively, a prosthetic conduit bearing a valve may be inserted from the apex of the left ventricle to the aorta.84 Asymmetric septal !rpertrophy may be repaired utilizing the approach of Morrow. The results of operative relief of discrete subvalvar aortic stenosis are quite good, with a mortality of approximately 5%. Almost all patients experience significant hemodynamic improvement, and most patients achieve a good long-term result. There is the potential of late morbidity due to recurrent or residual left ventricular outflow tract obstruction and to the development of aortic regurgitation. Relief of the diffuse forms of subaortic stenosis is much more difficult to achieve, and has a correspondingly higher operative mortality. Insufficient time has elapsed to provide sufficient data regarding the long-term outlook of these patients. Stenosis at the level of the aortic valve occurs due to deformity of the valve cusps. There may be associated narrowing of the aortic ring. The stenosis may occur in the form of a unicuspid, bicuspid, or tricuspid valve, or a thickened and deformed membranous valve without definable commissures. Infants who present with aortic stenosis associated with congestive heart failure are difficult to manage. Anticongestive therapy is rarely of significant benefit. Cardiac catheterization with measurement of left ventricular and aortic pressures and left ventricular cineangiography to assess left ventricular size and performance are usually carried out. With the development of two-dimensional echocardiography, there is some evidence that a thorough and accurate evaluation of these neonates is possible with noninvasive methods.86 Left ventricular function is ordinarily markedly reduced, and the left ventricle is small in a significant proportion of patients. Operation is indicated in the infants with congestive heart failure. A low ejection fraction is not a specific contraindication to valvotomy, as left ventricular function will improve in many of these infants following opening of the valve. Valvotomy may be performed on cardiopulmonary bypass or under inflow occlusion. The relatively poor overall results in this group may be explained on the basis of poor myocardial performance, which results from endocardial fibroelastoSEPTEMBER

CPS 27

sis, subendocardial ischemia, poor left ventricular compliance, and inadequate relief of obstruction. The hemodynamic status may be compromised further if aortic insufficiency is produced. Hypoplasia of the left ventricle is probably the most significant risk factor, and is associated with especially poor results.87 Older children with aortic valve stenosis have a much lower operative risk, and generally do quite well following valvotomy. Careful incision of the commissures usually enlarges the valve orifice and does not result in significant aortic insufficiency.88 Long-term studies indicate that aortic valvotomy is safe and effective, and gives excellent relief of symptoms.” Progressive aortic insufficiency or recurrent stenosis will develop occasionally and patients will require repeated valvotomy or valve replacement. Management of a small anulus at the time of aortic valve replacement can be accomplished by accepting a small to moderate gradient across a small-sized aortic prosthesis, or by performing the Konno procedure83; the Manouguian technique can also be used, in which case an incision is made in the posterior aspect of the aorta through the anulus at the commissure between the left and noncoronary sinus extending into the anterior mitral leaflet, and is widened with a Dacron patch.g0 Alternatively, the apical-aortic conduit may be considered.84 Supravalvar aortic stenosis may occur in either a localized or diffuse pattern. The commissures of the aortic valve are drawn into the supravalvar stenosing ring. The coronary ostia may be narrowed by the stenosing ring, or they may be obstructed due to adherence of a cusp to the aortic wall. Supravalvar stenosis may be repaired by partial excision of the stenosing ring plus widening of the aortotomy incision into the noncoronary sinus.g1 A more radical procedure involves an inverted Y-shaped incision, which enlarges the aortic narrowing by incising into the right and noncoronary sinuses with an inverted Y-shaped patch to close the aorta. This technique usually provides more predictable relief of aortic obstruction and subsequent improved function of the aortic valve.” Congenital Mitral Valve Malformations Inflow of the Left Ventricle

Causing

Obstruction

to

Functional obstruction of the mitral apparatus reduces pulmonary venous return to the left ventricle, which results in reduced left ventricular volume and elevated left atrial, pulmonary venous, and pulmonary artery pressures. Obstruction of the mitral valve is apparently well tolerated in fetal life. Symptoms and signs appear shortly after birth if the obstruction is severe. There will be evidence of poor cardiac output and respiratory distress. If obstruction is less severe, the children present beyond the neonatal period with a history of poor feeding, sweating, tachypnea, cough, and repeated pulmonary infections. 28

SEPTEMBER

CPS

There may be evidence of diminished peripheral perfusion on examination. Pulmonary hypertension causes an accentuated pulmonic component of the second heart sound. Usually there is a diastolic murmur heard best at the apex. One form of congenital mitral obstruction is the supravalvar ring. It may occur as an isolated condition or in conjunction with other mitral valve abnormalities. Resection of the ring usually provides adequate relief of the obstruction. There may be absent chordae tendineae or only short, thickened chordae associated with commissural thickening and fusion. This condition requires commissurotomy, fenestration of papillary muscles, and removal of secondary chordae. Abnormal excessive valvar tissue may obstruct the interchorda1 spaces. The anterior and posterior leaflets may also be joined by a large bridge of valvar tissue, thereby creating an accessory orifice. Resection of the bridge and removal of excessive obliterating interchordal tissue are necessary. One of the most frequent lesions causing mitral valve stenosis is the parachute mitral valve. All the chordae are attached to a single papillary muscle, and the interchordal spaces are obliterated. This condition is repaired by fenestrating the interchordal spaces and splitting the papillary muscle. In hypoplasia of the mitral valve, all components of the apparatus are small but normally formed. This is associated with a hypoplastic left ventricle and left ventricular outflow tract obstruction. In general, survival is dependent on left ventricular size. The majority of neonates with a left ventricle size 70% of normal will survive.g3 Medical management of children with congenital mitral stenosis consists principally of administration of digoxin and diuretics. Cardiac failure unresponsive to medical management requires relief of obstruction by reconstructive techniques or valve replacement. The major factor influencing immediate and longer-term results seems to be the degree of pulmonary vascular disease present preoperatively. Mitral valve reconstruction has been associated with a lower mortality than valve replacement. Valve replacement has about a 30% operative mortality and an actuarial five-year survival of 50%.‘* Right Ventricular Outflow Obstruction Potential areas of obstruction to right ventricular outflow include lesions of the right ventricle, the outflow tract of the right ventricle, the pulmonary valve and/or anulus, and the pulmonary arteries. Obstructive lesions may occur singly or in combination and be of varying severity. Associated cardiac lesions are common, especially ventricular septal defects. Patients with right ventricular outflow obstruction usually present with hypoxemia and cyanosis from inadequate pulmonary blood flow and a right-to-left shunt across an atria1 septal SEPTEMBER

CPS 29

defect or a patent foramen ovale. Severe obstruction may result in a right ventricular pressure higher than systemic pressure, often poorly tolerated and leading to arrhythmias or right ventricular failure. The aim of operative intervention is to increase pulmonary blood flow and to relieve obstruction of the right ventricle. Successful relief of right ventricular hypertension maximizes the chance for right ventricular growth and minimizes the development of subendocardial fibrosis and progressive hypertrophy of the right ventricle. Most commonly right ventricular outflow obstruction is due to pulmonary valve stenosis associated with an intact ventricular septum. There may be associated infundibular stenosis due to right ventricular hypertrophy. Usually the valvular lesion consists of three normal leaflets that are fused, resulting in a small central opening. The central opening is variable in diameter and may be only microscopic in size. The commissures are usually normally formed but are fused, and often adherent to the adjacent wall of the pulmonary artery. An associated atria1 septal defect or patent foramen ovale is common, and with complete occlusions is required for viability of a newborn. Neonates with critical pulmonary stenosis usually present in the first few days of life with severe right ventricular obstruction and a right-to-left shunt through an atria1 septal defect or patent foramen ovale. An infusion of prostaglandin is required to maintain patency of the ductus arteriosus, which should result in satisfactory pulmonary blood flow. As soon as the diagnosis has been established and the child’s condition has stabilized with administration of prostaglandins, a valvotomy is performed. Our preference in the newborn is the closed transventricular technique pioneered by Brock.’ A midline sternotomy provides optimal exposure for this procedure. An alternative is a retrograde transpulmonary valvotomy performed via a left thoracotomy. If this technique is chosen, special care must be exercised not to compromise flow through the ductus prior to the completion of the valvotomy. Studies of the natural history of the disorder have shown that minor pulmonary valve stenosis with a gradient less than 25 mm Hg rarely progresses. Patients with moderate pulmonary valve stenosis with a gradient between 25 to 50 mm Hg can be operated on or followed up and operated on if there is evidence of progressive stenosis. Valvotomy is recommended in children with a gradient greater than 50 mm Hg.s5 Operation is indicated whenever the patient becomes symptomatic and even in the absence of symptoms if the right ventricular pressure is above systemic. Open valvotomy performed under direct vision on cardiopulmonary bypass is the recommended technique except for critically ill neonates. In recent years, pulmonary valvotomy by balloon angioplasty has been performed with increasing frequency. 30

SEPTEMBER

CPS

The initial results have been quite satisfactory, but more longterm follow-up will be required to fully assess this procedure. In pulmonary valve dysplasia there are malformed, thickened leaflets with markedly decreased mobility. There may be associated hypoplasia of the pulmonary artery and a small pulmonary valve anulus. A simple valvotomy may well not relieve the pressure gradient. Adequate relief of obstruction usually requires complete excision of the dysplastic valve.g6 There may be an isolated infundibular stenosis of the right ventricle, which is possibly related to a ventricular septal defect that has subsequently closed. This lesion may present with varying degrees of dynamic and fixed obstruction. Surgical correction involves resection of obstructing muscle tissue with or without an associated outflow patch. Prominent anomalous muscle bands within the right ventricle may result in a double-chambered right ventricle. If obstruction is significant it may be relieved, on cardiopulmonary bypass, by a right ventriculotomy and resection of obstructing muscles. There may be stenosis of the main pulmonary artery, right or left pulmonary arteries (including their origin from the main pulmonary artery), and peripheral pulmonary arteries. Significant stenosis is relieved by incision and patch. Multiple peripheral pulmonary artery stenoses may occur in some patients. These stenoses are so numerous and so peripheral that successful repair is unlikely, and the condition is usually considered inoperable. Anomalous Pulmonary Venous Connection The four types of total anomalous pulmonary venous connection include the supracardiac, in which the pulmonary veins drain to the innominate vein through a vertical vein or directly to the superior vena cava; the cardiac, in which there is direct drainage into the right atrium or coronary sinus; the infracardisc, in which the vertical vein drains into the portal vein or inferior vena cava; and the mixed, which is a combination of two or more of the preceding types. Partial anomalous pulmonary venous drainage represents an incomplete form of this defect. Ordinarily, if only one pulmonary lobe drains into the systemic venous system in an anomalous fashion, no operative intervention is required. When more than one lobe drains into the systemic venous system, the resultant shunt is physiologically significant. In cases of total anomalous pulmonary venous connection there may be significant obstruction in the anomalous venous connection or at the level of the interatrial communication. In total anomalous venous connection, all venous blood from the pulmonary and systemic circuits enters the right atrium. If there is a small interatrial communication there will be only minimal right-to-left shunting, and the cardiac output will be reduced. A large inter-atria1 communication allows unobstructed SEPTEMBER CPS 31

distribution of mixed venous blood. That distribution will be determined by the relative compliances of the two ventricles and by the relative resistances in the systemic and pulmonary circulations. In neonates, the principal factor is the status of the pulmonary vascular bed, which is in turn largely determined by the presence or absence of pulmonary venous obstruction. In the absence of pulmonary venous obstruction, the pulmonary vascular bed will begin to mature after several days of life, the pulmonary resistance will fall, and the pulmonary flow will increase to three times or greater than the systemic flow. Congestive heart failure, manifested by tachypnea, tachycardia, dyspnea, poor feeding, and repeated respiratory infections will develop, usually beginning at about 1 month of age. Cardiac catheterization documents the site of anomalous connection by the step-up in oxygen saturation. Selective pulmonary arteriography is performed to document the presence and course of the anomalous connection. If pulmonary venous obstruction is present either at the interatria1 communication or due to extrinsic or intrinsic narrowing of the connecting vein, the high venous pressure is transmitted to the pulmonary capillary bed, often resulting in pulmonary edema. Reflex pulmonary arteriolar constriction results in worsening of pulmonary hypertension and diminished pulmonary blood flow. Cyanosis and tachypnea are usually present at or shortly after birth, and dyspnea and feeding difficulties develop early. Cardiac catheterization documents the site of oxygen step-up, a normal left atria1 pressure, a pulmonary artery pressure that is equal to the systemic pressure or higher, and an elevated pulmonary wedge pressure. Angiocardiographically, there is markedly delayed passage of dye through the pulmonary vasculature, and the anomalous venous connection is outlined. In recent years, the diagnosis of total anomalous pulmonary venous connection has been established definitely by cross-sectional echocardiography.” In some centers if the clinical, roentgenographic, and echocardiographic features are typical, the diagnosis and definitive plans for therapy are made without an accompanying cardiac catheterization. We have preferred to continue our policy of preoperative catheterization in order to carry out a complete hemodynamic assessment and angiographic visualization of the course of the anomalous connection. Usually, neonates and infants with symptomatic total anomalous pulmonary venous drainage present with severe failure and/or cyanosis and require urgent operative intervention. Intensive failure treatment usually provides only minimal temporary benefit, and most patients who are not operated on will die by 6 months of age. Occasionally, a patient with a wide interatria1 communication, no pulmonary venous obstruction, and just the right amount of pulmonary arteriolar constriction to 32 SEPTEMBER CPS

prevent excessive pulmonary flow can be operated on electively after 1 year of age. The first attempt at operative intervention in anomalous pulmonary venous connection was an anastomosis between the common pulmonary vein and the left atrium performed by Muller in 1951.” A successful repair of this condition using cardiopulmonary bypass was first reported by Cooley and Ochsner in 1957.” Typically, operative correction of this defect is carried out on severely symptomatic neonates utilizing the technique of deep hypothermia and circulatory arrest. As wide a communication as possible is created between the pulmonary veins and the left atrium. Despite recent improvements in early noninvasive diagnosis, preoperative preparation of desperately ill children, and improved myocardial preservation, the mortality rate in critically ill neonates remains 25% or greater.l”* lo1 Operative mortality is highest when there is obstruction to the anomalous pulmonary venous connection. This is most commonly the case in the infradiaphragmatic type. Generally, these patients are severely sick neonates with pulmonary edema, low cardiac output, and elevated pulmonary vascular resistance. Those patients who are operated on electively at several months of age or older are in much better condition prior to operation and do not have elevated pulmonary vascular resistance. In these cases the operative mortality is 10% or less. Long-term results in operative survivors are excellent, and late deaths due to pulmonary vascular disease or other complications are uncommon. Late anastomotic stricture or stenosis of the ostia of the pulmonary veins may occur.1oo DECREASEDPULMONARYBLOOD

FLOW

Decreased pulmonary blood flow is a prominent feature of a variety of congenital cardiac defects, the most common of which is tetralogy of Fallot. Other cyanotic conditions that the cardiac surgeon is called on to treat fairly commonly include pulmonary atresia with intact ventricular septum or with ventricular septal defect, tricuspid atresia, and Ebstein’s anomaly. The size of the right-to-left shunt in each lesion depends on the size of the inter-ventricular and/or interatrial connection and on the ratio of the resistances in the pulmonary and systemic circuits. Patients with these lesions will exhibit variable degrees of cyanosis, dyspnea on exertion, and exercise limitation. Tetralogy of Fallot The classic tetralogy of Fallot lesion consists of a ventricular septal defect, obstruction to pulmonary blood flow, right ventricular hypertrophy, and dextroposition of the aorta. The right and left ventricular pressures are equal, and the pulmonary artery SEPTEMBER

CPS 33

pressure may be normal or decreased, depending on the amount of obstruction to pulmonary blood flow. Patients with tetralogy of Fallot may present in one of the following ways: as newborns if the pulmonary stenosis is severe; as older infants, usually about 6 months of age, who have cyanotic spells with increasing activity; or later in childhood or young adult life. In all patients, the ventricular septal defect is virtually the same size relative to the size of the heart. The obstruction to pulmonary blood flow, usually caused by stenosis at the level of the pulmonary valve and by right ventricular outflow tract obstruction, is the principal determinant of the patient’s physiologic derangement and clinical presentation. Operative indications include resting systemic oxygen saturation less than or equal to 70%, hypercyanotic spells, or increasing cyanosis with polycythemia (hematocrit of 60% or greater). Preoperative cardiac catheterization is undertaken to visualize the right ventricular outflow tract and pulmonary artery. The diameters of the outflow tract, pulmonary valve anulus, and pulmonary arteries are vital factors in determining whether or not to proceed with primary correction or an initial palliative shunt. Angiocardiography is also carried out to define the presence or absence of multiple ventricular septal defects and the coronary artery anatomy. The left anterior descending coronary artery may originate from the right coronary artery. There may be a single coronary artery originating from the right sinus of Valsalva, and this coronary artery may give off a branch on the left side of the heart that passes anterior to the pulmonary outflow tract. These and other coronary artery anomalies may be difficult to define in the operating room because the anomalous coronary artery may run out of sight intramyocardially. The angiocardiogram is also helpful in documenting left and right ventricular size. A small ventricle is unusual, but can be present when associated with an overriding or straddling tricuspid valve. A small left ventricle may occur in older children who have had decreased pulmonary blood flow for several years. Left ventricular failure following total correction should not occur if the left ventricle has a volume greater than 60% of normal.102 The place of a palliative shunt procedure in children with tetralogy of Fallot is the subject of much investigation and discussion. Castaneda and co-workers have obtained excellent results with a policy of primary repair.lo3 In his series the incidence of residual ventricular septal defect is quite low, left ventricular function has been satisfactory, and there has been no evidence of recurrent obstruction to right ventricular outflow.‘04, lo5 The University of Alabama experience showed that young age, small size, high hematocrit reading, and the use of a transannular patch were incremental risk factors.lo6 As a general rule, if the combined diameter of the right and left pulmonary 34 SEPTEMBER CPS

arteries is less than one third the diameter of the ascending aorta, the initial procedure should probably be a shunt.io7 Our experience supports primary intracardiac repair in the majority of symptomatic patients with tetralogy of Fallot. However, age younger than 1 year and the requirement for a transannular patch are independent incremental risk factors for total repair. A preliminary palliative classical Blalock-Taussig shunt is performed in symptomatic infants younger than 1 year if a transannular patch would be required.“* The presence of a coronary artery anomaly that would compromise an incision in the right ventricular outflow tract is an indication for an initial palliative shunt. Intracardiac repair may be postponed until later, at which time it might be necessary to interpose an extracardiac conduit to restore right ventricle to pulmonary artery continuity, to avoid interruption of a hemodynamically significant source of coronary blood flow to the left ventricle. A preliminary shunt may allow the pulmonary artery a period of growth prior to total repair, and a shunt will help alleviate hypoxemia and polycythemia in the interim. Alternatively, the right ventricular outflow tract may be enlarged without closing the ventricular septal defect.log Complete repair usually involves a right ventriculotomy with closure of the ventricular septal defect with a prosthetic patch, relief of infundibular stenosis by excision of obstructing muscle bundles in the right ventricular outflow tract, and closure of the right ventricular outflow tract, commonly with a patch eFig 4). In some instances, it may be possible to close the ventricular septal defect from the right atria1 approach and to resect obstructing right ventricular outflow tract muscle through a combination of approaches from the right atrium and the pulmonary artery. If necessary, pulmonary valvotomy may be performed, and if there is a small pulmonary anulus a transannular patch using pericardium or prosthetic material is performed to enlarge the outflow tract. This may be extended on the main pulmonary artery if necessary. Hospital mortality for total repair in good risk patients is approximately 5% or less. Postoperative complications include excessive bleeding, low cardiac output, and heart block. Early postoperative heart failure occurs transiently in many patients. This seems to be especially true in those with an outflow patch and pulmonic valvular insufficiency. Long-term results following repair of tetralogy of Fallot have been quite good. Late deaths occur in approximately 2% of the operative survivors. Reoperation is necessary in approximately 2% for recurrent or residual ventricular septal defect and right ventricular outflow obstruction. A few patients will experience late postoperative heart fai1ure.i” This may be due to shunting from a ventricular septal defect, pulmonary regurgitation, or poor ventricular function. SEPTEMBER CPS

35

Fallot’s tetralogy, fects. New York,

Fig 4.-Total correction of tetralogy of Fallot. A, vertical right ventriculotomy. If the pulmonary valve annulus is hypoplastic the incision is carried out on to the main pulmonary artery. B, interrupted horizontal mattress sutures with pledgets are placed around the edges of the ventricular septal defect, carefully avoiding the conduction system. The sutures are then passed through a patch that is lowered into place and the sutures tied. C, if necessary, a transannular patch is utilized to close the right ventricular outflow tract once the obstructing muscle bundles have been resected. (From Castaneda AR., et al.: in Stark J., de Leval M. (eds.): Surgery for Congenital Heart DeGrune & Stratton, Inc., 1983, pp. 321-329. Used by permission.)

In one study, patients were evaluated for serious arrhythmias more than five years after surgical correction of tetralogy of Fallot. Forty-two percent manifested serious ventricular arrhythmias during treadmill exercise or 24-hour ambulatory ECG monitoring. Patients with ventricular arrhythmias were older than patients without arrhythmias both at the time of operation and subsequent evaluation. Residual elevation of right ventricular systolic and diastolic pressures did not appear to influence the incidence of arrhythmias.“’ Another study showed that phenytoin was successful in supressing significant ventricular arrhythmias in patients in the late period after operation. Arrhythmias were decreased in all patients and completely suppressed in the majority.“” Pulmonary

Atresiu

With Intact

Ventricular

Septum

Complete atresia of the pulmonary valve may be associated with an intact ventricular septum and varying degrees of hypoplasia of the right ventricle. In this anomaly, the pulmonary cusps fuse and form a diaphragm-like membrane. The pulmonary valve anulus and main pulmonary trunk are generally hy36 SEPTEMBER CPS

poplastic as well. There is great variation in the size and degree of development of the right ventricle. Any or all of the three portions

of the right

ventricle

may be underdeveloped.‘i3

soidal channels often arise from the right ventricular and connect

with

the coronary

arteries.

Sinu-

trabeculae

These channels

allow

egress of blood during ventricular systole from the obstructed right ventricle to the systemic circulation via the coronary arteries.114 Most of these neonates present in severe respiratory distress with deep cyanosis and require treatment with oxygen, correction of acid-base disturbance, and improvement of pulmonary blood flow with

the use of prostaglandin

El. After

have stabilized,

operation

to improve

is undertaken

blood flow. If there is a patent

ventricle, prefer

then a pulmonary

infundibular

valvotomy

the closed transventricular

versy persists as to whether combined

with

some form

the children

portion

pulmonary of the right

may be performed.

technique

of Brock.

or not this procedure of a systemic

We

Contro-

needs to be

to pulmonary

artery

shunt. Alternatively, an infusion of prostaglandin El may be maintained postoperatively in an attempt to provide pulmonary blood flow via a patent ductus arteriosus until the right ventricle is able to provide more effective forward pulmonary blood flow.107 A successful pulmonary valvotomy may result in some growth in the size of the right ventricle, Elevated right ventricular end-diastolic

but short of normal.‘15 pressure and right-to-

left shunt across an atria1 septal defect or patent usually

persist postoperatively

ful in relieving Subsequent

the pulmonary reparative

foramen

even if the valvotomy

ovale

is success-

stenosis.

procedures

are necessary

in many

of

the children who undergo an initial valvotomy with or without an associated shunt. Usually a subsequent valvotomy is performed and/or the right ventricular outflow tract is widened with

a patch

struction. reasonably

to relieve

residual

If the right ventricle good contractile

right

attains

function

ventricular

an adequate

outflow

ob-

size and has

then closure of a previous

shunt and closure of the residual atria1 septal defect or patent foramen ovale are undertaken. Infants with extremely hypoplastic right ventricles may not show adequate growth of the ventricle even after a successful valvotomy with or without a shunt. Children

who survive

palliative

procedures

and subsequently

have an inadequately sized right ventricle and adequate pulmona arteries may be candidates for a Fontan-type procedure.’ 7 6 Pulmonary Atresiu With Ventricular Septal Defect This lesion can be considered an extreme example of tetralogy of Fallot. The unique feature of this lesion is the existence of some bronchopulmonary segments that are connected to central pulmonary arteries and/or to segmental aortopulmonary collateral arteries. Usually, patients with this defect present as neoSEPTEMBER CPS

37

nates with severe cyanosis and decreased perfusion of the lung fields. Occasionally, a patient will present in congestive heart failure due to excessive pulmonary blood flow through the systemic to pulmonary collateral arteries. Detailed investigation, including precise definition of the intracardiac anatomy, especially the presence or absence of a ventricular septum and a right ventricular outflow tract, are required. The variable blood supply to the lungs should be defined as carefully as possible. It is necessary to define the central pulmonary arteries, the connections between the central pulmonary arteries and the right ventricle, and the destination and distribution of these central arteries within the lungs. A complete evaluation of all systemic to pulmonary collateral arteries must be undertaken. Sometimes pulmonary vein wedge angiography is necessary to visualize the central pulmonary arteries. Usually, the right and left pulmonary arteries are confluent and form a characteristic Y-shaped vessel suggestive of a seagull. Detailed anatomical and hemodynamic studies are necessary to plan the best method of operative repair. Ideally, the right ventricle will eventually be connected to a centrally joined pulmonary circulation.r17 Some patients have confluent pulmonary arteries that perfuse most if not all of the bronchopulmonary segments. In these patients, the size of the right and left pulmonary arteries determines whether or not a total corrective procedure may be undertaken safely.“’ The sizes of the right and left pulmonary arteries and the aorta at the level of the diaphragm are determined by angiography. A combined cross-sectional area of the right and left pulmonary arteries that is at least half the crosssectional area of the aorta means that the pulmonary arteries are adequate to receive the cardiac output and prevent excessive right ventricular hypertension following repair. This method of assessing operability has been defined further by others.‘lg Neonates usually present with ductus-dependent pulmonary circulation and extreme cyanosis. This can be effectively palliated temporarily with prostaglandin El to keep the ductus open until such time as a shunt can be performed. Infants who require improved pulmonary blood flow and those older children in whom the predicted postoperative right ventricular pressure is excessive should undergo a palliative shunt, usually a classical Blalock-Taussig shunt or modified Blalock-Taussig shunt using polytetrafluoroethylene. An alternative to the shunt is enlargement of the right ventricular outflow tract with a y;tch utilizing cardiopulmonary bypassr2’ or a closed technique. In either case, the ventricular septal defect is left open. Occasionally, a patient with pulmonary atresia and ventricular septal defect will present with severe congestive heart failure due to excessive pulmonary blood flow resulting from large aortopulmonary collateral arteries or a patent ductus arteriosus. The collateral arteries or the ductus arteriosus may be ligated if there 38 SEPTEMBER CPS

is an adequate source of pulmonary blood flow through the central pulmonary arteries. Otherwise, the source of collateral flow should be banded and not completely ligated, or the source of collateral flow should be connected to the central pulmonary arteries utilizing a shunt procedure. Palliative procedures in this group carry a significant mortality, and even if palliation is successful the pulmonary anatomy may not prove to be amenable to eventual total correction. A complete repair of this lesion, including closure of the ventricular septal defect and connection of the right ventricle to the central pulmonary arteries, ordinarily is not undertaken until age 4 or 5 because an extracardiac conduit is required. A child this age is usually large enough for insertion of a conduit that will not be rapidly outgrown. The definitive procedure carries a mortality of 10% to 15%.11g, lz2 Pronounced right ventricular hypertension early after repair is the primary determinant of mortality, which is in turn determined by the size of the pulmonary arteries and the pulmonary vascular resistance. Tricuspid Atresia In tricuspid atresia there is complete agenesis of the tricuspid valve, and no direct communication between the right atrium and the right ventricle. Other typical findings include an interatria1 septal defect, varying degrees of hypoplasia of the right ventricle, and some communication between the systemic and pulmonary circulations. Normal ventriculoarterial connection is present in the majority of cases, but there may be transposition in which the aorta arises from the small outlet chamber. Pulmonary atresia or stenosis is seen in the majority of cases with transposition and in about one third of the cases without transposition.123 The pulmonary blood flow is determined by the specific anatomical findings in each case. It is decreased in the presence of pulmonary stenosis and/or a small ventricular septal defect. If there is no pulmonary stenosis present and the ventricular septal defect is large, the pulmonary blood flow will be excessive and the child will present in congestive heart failure due to a large left-to-right shunt. Treatment of patients with tricuspid atresia requires operative intervention. Palliative procedures are designed to improve pulmonary blood flow with a shunt if pulmonary flow is diminished, and to reduce pulmonary blood flow with a pulmonary artery band if it is excessive. Prostaglandin El infusion intravenously may be utilized in neonates with severe hypoxemia due to poor pulmonary blood flow dependent on the ductus arteriosus. Patency of the ductus is maintained until the shunt has been completed. Most patients with tricuspid atresia will require some operative intervention during the first year of life. The most common indication for operation is cyanosis due to decreased pulmonary blood flow. Infants who require a shunt usually undergo a clasSEPTEMBER CPS

39

sical Blalock-Taussig anastomosis or a modified Blalock-Taussig shunt with a polytetrafluoroethylene prosthesis. Results with the Glenn shunt are unsatisfactory in children younger than 6 months because at this age the pulmonary arteries are small and there is increased pulmonary vascular resistance.124 In older children, the Glenn shunt is preferred, as it does not lead to an increased volume load on the left side of the heart, and will deliver approximately one third of the total systemic venous blood directly into the pulmonary artery at low pressure. In addition, it may serve as a first-stage procedure for a subsequent right atria1 to pulmonary artery anastomosis. Infants who are in congestive heart failure and do not respond to maximal medical management may have to undergo pulmonary artery banding. Usually, children’s conditions are greatly improved following an initial shunt procedure, but subsequently they may develop recurrent cyanosis and falling exercise tolerance as the shunt fails, or they outgrow the shunt. Additional causes for the subsequent development of poor pulmonary flow include an increase in the degree of pulmonary stenosis or a decrease in the size of the ventricular septal defect. A second surgical procedure is then indicated, either another palliative shunt or a Fontan-type procedure. The Fontan procedure, a physiologic corrective operation for tricuspid atresia,125 or one of its modifications, is currently the technique of choice in appropriate candidates. The best results of operation are obtained in those patients who meet the following criteriai2! 1. Minimum age of 4 years 2. Normal sinus rhythm 3. Normal right superior and inferior vena cava 4. Normal volume right atrium 5. Mean pulmonary artery pressure of 15 mm Hg or less 6. Pulmonary arteriolar resistance less than 4 unit&q m 7. Pulmonary artery to aorta diameter ratio of 0.75 or greater 8. Normal right and left ventricular function 9. Competent left atrioventricular valve 10. No distortion of pulmonary arteries by a previous shunt. Satisfactory results may be obtained in patients who do not fall within the Fontan criteria,127 although the risk of operation is higher and the long-term outlook not as good. The operation includes closure of the atria1 septal defect and ligation of the main pulmonary artery just above the pulmonary valve. The right atrium is connected to the pulmonary artery either via a direct anastomosis or with a conduit, generally one that contains a valve. Alternatively, a right atria1 to right ventricular anastomosis, with or without a valve, may be performed.12’ If the right ventricle is included in the pulmonary circuit, the bulboventricular for-amen must be closed, and the 40 SEPTEMBER

CPS

patient must have a nonobstructed pathway for flow to reach the pulmonary artery. Some authors prefer to incorporate a heterograft or homograft valve between the right atrium and the outlet chamber. Bjork et al. 12’ have described a direct connection of the right atria1 appendage to the outlet chamber supplemented anteriorly with a pericardial patch. The latter technique has the theoretical advantage of utilizing only autogenous material and the avoidance of possible subsequent conduit and/or valve stenosis. It has the disadvantage of the absence of a one-way valve interposed between the right atrium and right ventricle. This may result in significant regurgitation into the right atrium. Operative mortality for this procedure ranges from 10% to 15%. To maintain an adequate cardiac output postoperatively, in most patients a high right atria1 filling pressure is required. Pleural effusions and ascites are common. Late problems related to obstruction of conduits include narrowing at the anastomosis between the conduit and the heart or pulmonary artery, increasing buildup of a fibrous peel on Dacron tube grafts, and calcification with eventual stenosis of heterograft tissue valves. Normal sinus rhythm is important, as atria1 systole rovides the major pulsatile support of pulmonary blood flow. Ro Howevy;{ some patients tolerate nodal rhythm and atria1 fibrillation. This ability to tolerate arrhythmias in the face of a Fontan procedure has been documented experimentally.132 Most patients who survive operation have experienced marked and long-lasting symptomatic improvement. If a subpulmonary ventricular chamber is utilized in the Fontan circulation, this chamber may grow sufficiently in the postoperative period to provide a right ventricle-dependent pulmonary circulation with a right atria1 pressure lower than the mean pulmonary artery pressure.133 Early postoperative studies have shown little benefit of incorporating a subpulmonary ventricular chamber, but its use may provide a more normal circulation in the long term. This may lead to better late results following Fontan-type operations. The majority of late survivors are greatly improved and in functional class 1 or 2.134 However, significant hemodynamic abnormalities may be found in late survivors of the Fontan procedure when valved conduits are utilized to connect the right atrium and pulmonary artery. In one study the mean right atria1 pressure at rest was approximately 15 mm Hg, but with exercise this rose to 25 mm Hg.135 Ebsteids

Anomaly

The primary unifying feature of Ebstein’s anomaly is the abnormal downward displacement of the tricuspid valve orifice into the right ventricle. The septal and posterior leaflet attachments are displaced, whereas the anterior leaflet attachment is normally placed. There is redundancy of valve tissue and adherence of variable portions of the septal and posterior leaflets to SEPTEMBER CPS

41

the right ventricular wall. Redundancy involves all valve leaflets, but the anterior cusp is usually less affected. The right ventricle is divided into two parts by the displaced tricuspid valve. That portion of the right ventricIe between the atrioventricular junction and the downward displaced atrioventricular valve forms a common chamber with the right atrium and is said to be “atrialized.” Right ventricular functional impairment depends on the extent of atrialization of the right ventricular inflow portion and on the intimacy of adherence of the valve to the right ventricular wall. The trabecular and infundibular portions of the right ventricle constitute that portion that is functional. The atrialized portion of the right ventricle usually is thinwalled and shows a varying amount of dilatation. Associated anomalies are common, including atria1 septal defect, pulmonary stenosis or atresia, and ventricular septal defect. The functional abnormalities caused by this anomaly are highly variable and may include tricuspid valve incompetence, relative tricuspid stenosis due to obstruction of inflow into the functioning right ventricle, a small functional right ventricle, paradoxical motion of the atrialized portion of the right ventricle, right-to-left shunt at the atrial level, and arrhythmias. Operative intervention in patients with Ebstein’s anomaly is indicated when there is severe cyanosis, or congestive heart failure, or severe arrhythmia. Recurrent supraventricular tachycardia is a sufficiently frequent complicating feature to warrant intraoperative mapping studies or at least a preoperative electrophysiologic study in virtually all patients. Ablation of a Kent bundle is an effective means of controlling reentrant supraventricular tachycardia. 136 If there is cyanosis, the atria1 septal defect can be closed and obstruction of flow into the right ventricle must be relieved, usually with a tricuspid valve replacement. Patients may present with congestive heart failure due to regurgitation into the right atrium. If there is primarily tricuspid insufficiency accompanied by a large, functioning right ventricle then the patient may be a suitable candidate for a reparative procedure. Repair consists of plication of the atrialized portion of the right ventricle plus a tricuspid annuloplasty.137 The major disadvantage of this technique is that suture plication cannot be accomplished along the septal leaflet because the septum cannot be plicated and because of the danger of injury to the conduction system. In those patients who present predominantly with obstruction to flow between the right atrium and right ventricle, tricuspid valve replacement is necessary. A prosthetic or tissue valve is inserted at the site of the normal tricuspid valve anulus. Some authors have recommended suturing of the valve cephalad to the coronary sinus orifice in order to place the coronary sinus orifice in a subvalvular position and to avoid the conduction system.138 Tricuspid valve replacement may be 42

SEPTEMBER

CPS

accompanied by plication of the atrialized portion of the right ventricle. Previously, the mortality rate for surgical intervention in Ebstein’s anomaly was quite high, approximating 40% to 60%. Recent experiences have shown much improved mortality figures, ranging from 7% to 17%.13’, 14’ These recent reports also show marked symptomatic improvement in most patients at late follow-up. Late deaths, which are infrequent, occurred in patients with large hearts and major preoperative ventricular arrhythmias. Late deaths were principally due to arrhythmias and to persistent tricuspid regurgitation in patients who had not undergone valve replacement. If there is severe hypoplasia of the right ventricle associated with this condition then the proper operative correction might include the creation of a Fontan-type circulation. This would entail closure of the atria1 septal defect and tricuspid valve orifice with appropriate patches and connection of the right atrium to the pulmonary arteries either by direct anastomosis or with a conduit. ADMIXTURE

In transposition of the great arteries, the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. In this disorder the systemic and pulmonary circuits function in parallel, with nonoxygenated systemic venous blood being circulated through the aorta, and oxygenated pulmonary venous blood being circulated through the pulmonary artery to the lungs. Obviously, to support life, an interchange must be present between the two circuits at the atrial, ventricular, or great arterial level. The sum total of the shunting back and forth between the two circuits must be equal, otherwise one limb of the circulation would drain completely into the other. Transportation of the great arteries results in a deficient oxygen supply to the body tissues due to the inability to transfer a sufficient quantity of oxygenated pulmonary venous blood to the systemic circuit. The cardiac output in the pulmonary circuit is independent, and is usually excessive. As a consequence, pulmonary vascular obstructive disease is virtually inevitable and will lead to the early death of many infants unless surgical intervention is undertaken. Transposition

of the Great Arteries

Intense cyanosis in the first few days of life is the usual presentation of infants who have transposition of the great arteries without an associated ventricular septal defect or patent ductus arteriosus. Usually, these infants require emergency cardiac catheterization and balloon atria1 septostomy. In almost all SEPTEMBER CPS

43

cases this results in an adequate interatrial communication, satisfactory mixing between the pulmonary and systemic circuits, and improvement in systemic oxygenation and acid-base status. In most centers, right and left ventricular cineangiocardiography are performed along with measurements of intracardiac pressures. If possible, one assesses the presence or absence of pulmonary stenosis. Most infants who have simple transposition and an adequate balloon atria1 septostomy do well; there still is a significant mortality and morbidity during the first year of life following this procedure,141 so that it cannot be considered definitive. If considerable clinical improvement is not achieved by balloon septostomy, the patient’s condition is reassessed with twodimensional echocardiography to determine the size of the interatria1 communication. If it seems to be too small, a Blalock-Hanlon septectomy is performed to enlarge the interatrial communication.3 This almost always results in adequate mixing and symptomatic improvement. The usual policy is to restudy these children at approximately 6 months of age to assess pulmonary flow, pressure, and resistance. Right and left ventricular function can be assessed with cineangiocardiography. Elective operation in patients with simple transposition is performed within the first year of life. Progressive cyanosis and polcythemia with a hematocrit of 60% or greater, or a resting systemic oxygen saturation less than 60% are indications for earlier operation. Symptomatic children usually undergo intra-atria1 repair, but if there is an associated relative hypoplasia of one of the ventricles, or left ventricular outflow obstruction, with or without a ventricular septal defect, definitive repair is deferred and the child undergoes a BlalockHanlon surgical septectomy as an initial palliative procedure.3 In 1964, Mustard reported the use of a pericardial patch to separate the systemic and pulmonary circulation.142 In the Mustard procedure, most of the atria1 septum is excised, and a baffle is made using pericardium or prosthetic patch material to direct pulmonary venous return to the tricuspid valve orifice, and to direct the systemic venous return to the mitral valve orifice. Hospital mortality in children operated on during the first year of life is between 2% and 5%. The advantages of an early definitive repair vs. a delayed two-stage correction following a preliminary Blalock-Hanlon procedure have been well documented. The procedure is easier in patients who are at least four to six months of age because the heart is sufficiently large to allow the creation of unobstructed channels for the pulmonary and systemic venous blood. Some infants have undergone intraatria1 correction during the first few of weeks of life. The results of these early interventions have generally been good with a low operative mortality. However, in the placement of the intraatria1 baffle, care must be taken to avoid systemic venous or pulmonary venous obstruction. 44 SEPTEMBER

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Despite the overall good long-term results following the Mustard procedure, there is some late mortality and morbidity. Asymptomatic patients who undergo exercise testing show diminished exercise performance.144 Significant right ventricular dysfunction may occur following this procedure.145 Late right ventricular dysfunction may be due to several factors: inadequate intraoperative protection of the myocardium, preoperative hypoxemia (which may lead to subsequent myocardial fibrosis), or the right ventricle being utilized as the systemic ventricle. In addition, there may be significant troublesome postoperative arrhythmias. The Senning procedure, an alternative form of intra-atria1 correction, is now generally preferred (Fig 5).16 This procedure has been the focus of increasing interest in recent years because it requires none or only a very small amount of nonviable material in the repair. All pathways are created with intrinsic cardiac tissue, and this allows the potential for future growth of critical areas in the systemic venous and pulmonary venous pathways. It is possible that this procedure also provides better preservation of atria1 function. Revival of interest in this procedure has been stimulated by technical modifications.147 The use of intrinsic cardiac tissues to form the pathways allows the surgeon to perform this procedure in patients at any age rather than wait for four to six months as in the Mustard procedure, and the results are comparable. Collected results show a hospital mortality of approximately 3% to 4%. Late results following this procedure have been good, and there have been relatively few difficulties associated with obstruction of either venous pathway. The majority of patients remain in sinus rhythm, but there is a small incidence of troublesome arrhythmias. In those patients with transposition of the great arteries associated with a ventricular septal defect, usually there is adequate oxygenation early in life. Cyanosis is mild to moderate, and the usual presentation is that of congestive heart failure within the first two months of life. Heart failure is managed medically, and the children are catheterized to determine the size and location of the ventricular septal defect, pulmonary vascular resistance, the presence or absence of obstruction to the left ventricular outflow tract, and the presence or absence of abnormal position of the atrioventricular valve. If congestive heart failure cannot be controlled medically then pulmonary artery banding or definitive repair must be undertaken. In general, pulmonary artery banding is not performed, and the anomaly is corrected by a one-stage procedure. The corrective options include closure of the ventricular septal defect with associated intra-atria1 repair or an arterial switch procedure. If there is an associated left ventricular outflow tract obstruction, the children usually are given initial palliation and undergo a Rastelli procedure at 4 to 5 years of age.14’ Early and late results of this SEPTEMBER CPS 45

Fig 5.-Senning operation for transposition of great arteries. A, the right atrium is opened, and a flap of interatrial septum is developed. It remains attached at the interatrial groove. If necessary, the flap may be supplemented with dacron or pericardium. B, the septal flap is sutured in the lefl atrium between the left atrial appendage &AA) and the left pulmonary veins (LP V). The inferior and superior borders of the flap are then sutured. C, the caval pathways are created by suturing the right side of the incised free right atrial wall to the rim of the atrial septal defect. A previous incision has been made just anterior to the right pulmonary veins. D, the lefthand side of the incised free right atrial wall is sutured over the caval pathways and to the right of the left atriotomy to complete the pulmonary venous pathway. (From Pacific0 A.D.: Concordant transposition-Senning operation, in Stark J., de Leval M. (eds.): Surgery for Congenital Heart Defects. New York, Grune & Stratton, Inc., 1983, pp. 345-352. Used by permission.)

procedure have been quite satisfactory.14’ Operative mortality is approximately 10% and late complications associated with residual ventricular septal defect, conduit infection, or conduit obstruction occur in lo%-20% of these patients. Jatene and colleagues reported the first successful results with an arterial switch procedure (Fig 6).15’ The primary determinant of success of this procedure is the capability of the left ventricle to support the systemic circulation. Satisfactory left ventricular function is possible only if there is preexisting increased resistance to left ventricular output or a preexisting volume load 46 SEPTEMBER CPS

Fig 6.-Transposition of the great arteries-arterial switch operation. A, after closure of the ventricular septal defect through a right atrfotomy, the ascending aorta (Ao) and pulmonary artery (PA) are transected. Marking sutures are placed on the pulmonary artery externally to identify the commissures. B, the distal segment of aorta is brought behind the pulmonary artery bifurcation and anastomosed to the proximal segment of the pulmonary artery. A significant discrepancy in the diameters of the great arteries may be compensated for by incising the distal aortic segment anteriorly (inset). C, the ostium of each coronary artery with a surrounding cuff of aortic tissue is excised from its sinus. Each coronary artery is mobilized to permit relocation to the new systemic great vessel, the former pulmonary artery. LAD, left anterior descending. D, buttons are cut out of the new “aorta,” and the coronary arteries are inserted in their respective sites. E, the distal main pulmonary artery is tailored and anastomosed to the proximal aorta, coming from the right ventricle, thus completing the arterial switch. RCA, right coronary artery. (From Pacific0 A.D., et al.: Repair of transposition of the great arteries with ventricular septal defect by an arterial switch operation. Circulation 68 [suppl. 2]:1 l-49, 1983. Used by permission of the American Heart Association, Inc.)

on the left ventricle. In patients with simple transposition and none of these features, Yacoub et al. have prepared the left ventricle for an arterial switch procedure by a prior pulmonary artery banding.151 A small number of children with simple transposition have undergone the arterial switch procedure in the neonatal period. During this time the pulmonary vascular resistance remains relatively high, and the left ventricle has been “conditioned” by this increased work load. The preliminary results of this management scheme have been satisfactory, but they are inconclusive. Currently, in patients with simple transposition, a Mustard or Senning procedure with an operative mortality of 5% or less is the operative treatment of choice. However, improving results with pulmonary artery banding in the neonatal period followed by arterial switching may eventually lead to a change in operative treatment. Postoperative studies in patients who have undergone the arterial switch procedure have shown normal left and right ventricular function as assessed by ejection fraction and pressure measurements. The SEPTEMBER

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great arterial anastomoses appear intact and appear to grow, and arrhythmias are uncommon. Concern remains regarding the possibility of future development of coronary ostial stenosis and aortic insufficiency. Patients with transposition of the great arteries and ventricular septal defect have a particular tendency to develop elevated pulmonary vascular resistance. If this occurs, closure of the ventricular septal defect is contraindicated. A palliative Mustard operation without closure of the ventricular septal defect has been accomplished with low risk and impressive long-term hemodynamic and clinical improvement.152, ’ 3 CONCLUSION Over the past five decades, great advances have been made in the surgical treatment of congenital heart disease. We now possess a tremendous body of knowledge regarding the relationship between cardiovascular morphology and function, the natural history of the various lesions, and the results of surgical intervention. However, there is much that remains to be learned. Future progress will derive from continued aggressive attempts at palliation or correction of the various malformations encountered in these patients, careful follow-up and scrutiny of the results of surgical intervention, and basic research in the areas of myocardial protection of the immature and hypertrophied heart, reperfusion injury, and the physiology of cardiopulmonary bypass. REFERENCES 1. Gross R.E., Hubbard J.P.: Surgical ligation of patent ductus arteriosus: Report of first successful case. J.A.Md. 112:729, 1939. 2. Brock R.C.: Pulmonary valvulotomy for the relief of congenital pulmonary stenosis: Report of three cases. Br. MecE. J. 1:1121, 1948. 3. Blalock A., Hanlon C.R.: The surgical treatment of complete transposition of the aorta and pulmonary artery. Surg. Gynecol. Obstet. 90:1, 1950. 4. Gross R.E., Watkins E. Jr.: Surgical closure of atria1 septal defects. Arch. Surg. 67:670, 1953. 5. Gibbon J.H., Jr.: Application of a mechanical heart and lung apparatus to cardiac surgery. Minn. Med. 37:171, 1954. 6. Warden H.E., Cohen M., Read R.C., et al.: Controlled cross circulation for open intracardiac surgery; physiologic studies and results of creation and closure of ventricular septal defects. J. Thorac. Sum. 28:331, 1954. I. Bargeron L.M., Elliot L.P., Soto B., et al.: Axial cineangiography in congenital heart disease: I. Concept, technical and anatomic considerations. Circulation 56:1075, 1977. 8 Elliott L.P., Bargeron L.M., Bream P.R., et al.: Axial cineangiography in congenital heart disease: II. Specific lesions. Circulation 56:1084, 1977. 9. Tajik A.J., Seward J.B., Hagler D.J., et al.: Two-dimensional real-time ultrasonic imaging of the heart and great vessels: Technique, image orientation, structure identification, and validation. Mayo Clin. Proc. 53:271, 1978. 10. Adams F.H.: Fetal and neonatal circulations, in Adams F.H., Emmanouilides G.C. (eds.): Heart Disease in Infants, Children, and Adolescents. Baltimore, Williams & Wilkins, 1983, p. 13. 48 SEPTEMBER CPS

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ment of patients with ventricular septal defect and pulmonary hvpertension: Response to intense upright exercise. Circulation 48:864, i97$.34. Cordell D.. Graham T.P. Jr., Atwood G.F.. et al.: Left heart volume characteristics following ventricular septal defect closure in infancy. Circulation 54:294, 1976. 35. Graham T.P. Jr., Cordell G.D., Bender H.W. Jr.: Ventricular function following surgery, in Rowe R.D., Kidd B.S.L. (eds.): The Child With Congenital Heart Disease After Surgery. Mount Kisco, N.Y., Futura, 1976, p. 277. 36. Rastelli G.C., Kirklin J.W., Titus J.L.: Anatomic observations on complete form of persistent common atrioventricular canal with special reference to atrioventricular valves. Mayo Clin. Proc. 41:296, 1966. 37. Pacific0 A.D.: Atrioventricular septal defects, in Stark J.S., de Leval M. (eds.): Surgery for Congenital Heart Defects. London, Grune & Stratton, 1983, p. 289. 38. Studer M., Blackstone E.H., Kirklin J.W., et al.: Determinants of early and late results of repair of atrioventricular septal (canal) defects. J. Thoroc. Cardiovasc. Surg. 84:523, 1982. 39. McMullan M.H., McGoon D.C., Wallace R.B., et al.: Surgical treatment of partial atrioventricular canal. Arch. Surg. 107:705, 1973. 40. Bender H.W. Jr., Hammon J.W. Jr., Hubbard S.G., et al.: Repair of atrioventricular canal malformation in the first year of life. J. Thorac. Cardiovast. Surg. 84515, 1982. 41. Berger T.J., Black&one E.H., Kirklin J.W., et al.: Survival and probability of cure without and with operation in complete atrioventricular canal. Ann. Thorac. Surg. 27:104, 1979. 42. Berger T.J., Kirklin J.W., Blackstone E.H., et al.: Primary repair of complete atrioventricular canal in patients less than 2 years old. Am. J. Cardial. 41:906, 1978. 43. Bull C., Deanfield J., de Leval M., et al.: Correction of isolated secundum atria1 septal defect in infancy. Arch. Dis. Child. 56:184, 1981. 44. Di Sesa V.J., Cohn L.A., Grossman W.: Management of adults with congenital bidirectional cardiac shunts, cyanosis, and pulmonary vascular obstruction: successful operative repair in three patients. Am. J. Cardiol. 51:1495, 1983. 45. Brute1 de la Riviere A., Brom G.H.M., Brom A.G.: Horizontal submammary skin incision for median sternotomy. Ann. Thorac. Surg. 32:101, 1981. 46. Meyer R.A., Karfhagen J.C., Covitz W., et al.: Long-term followup study after closure of secundum atrial septal defect in children: An echocardiographic study. Am. J. Cardiol. 50:143, 1982. 47. Clark E.B., Kugler J.D.: Preoperative secundum atria1 septal defect with coexisiting sinus node and atrioventricular node dysfunction. Circulation 65:976, 1982. 48. Collett R.W., Edwards J.E.: Persistent truncus arteriosus: A classification according to anatomic types. Surg. Clin. North Am. 293245, 1949. 49. Marcelletti C., McGoon D.C., Mair D.: The natural history of truncus arteriosus. Circulation 54108, 1976. 50. Singh A.K., de Leval M.R., Pincott J.R., et al.: Pulmonary artery banding for truncus arteriosus in the first year of life. Circulation 54(suppl. 3):17, 1976. 51. Stark J., Gandhi D., de Leval M., et al.: Surgical treatment of persistent truncus arteriosus in the first year of life. Br. Heart J. 40:1280, 1978. 52. Mair D.D., Ritter D.G., Davis G.D., et al.: Selection of patients with truncus arteriosus for surgical correction: Anatomic and hemodynamic considerations. Circulation 49:144, 1974. 53. De Leval M., McGoon D.C., Wallace R.B., et al.: Management of truncal valvular regurgitation. Ann. Surg. 180:427, 1974. 54. Marcelletti C., McGoon D.C., Danielson G.K., et al.: Early and late results of surgical repair of truncus arteriosus. Circulation 55:636, 1977. 55. Maron B.J., Humphries J.O., Rowe R.D., et al.: Prognosis of surgically cor50 SEPTEMBER CPS

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perience with surgical repair of coarctation of the aorta. J. Thorac. Cardiovase. Surg. 771217, 1979. Celoria G.C., Patton R.B.: Congenital absence of the aortic arch. Am. Heart .I. .58:407. 1959. Litwin S.B., Van Praagh R., Bernhard W.F.: A palliative operation for certain infants with aortic arch interruption. Ann. Thorac. Surg. 14:369, 1972. Spencer F., Neil1 C., Sank L., et al.: Anatomical variations in 46 patients with congenital aortic stenosis. Ann. Surg. 26:204, 1960. Bjornstad P.G., Rastan H., Keutel J., et al.: Aortoventriculoplasty for tunnel subaortic stenosis and other obstructions of the left ventricular outflow tract: Clinical and hemodynamic results. Circulation 6059, 1979. Konno S., Imal Y., Iida Y., et al.: A new method for prosthetic valve replacement in congenital aortic stenosis associated with hypoplasia of the aortic valve ring. J. Thoruc. Cardiovasc. Surg. 70:909, 1975. Norman J.C.. Nihill M.R.. Coolev D.A.: Valved anico-aortic comnosite conduits for left ventricular ‘outflow tract obstructions: A 4 year ‘experience with 27 patients. Am. J. Cardiol. 45:1265, 1980. Morrow A.G.: Hypertrophic subaortic stenosis: Operative methods utilized to relieve left ventricular outflow obstruction. J. Thorac. Cardiovasc. Surg. 761423, 1978. Sink J.D.. Smallhorn J.F., Macartnev F.J.. et al.: Management of critical stenosis in infancy. J. Thorac. Card&asc. Surg. 87:82, 1984. Hammon J.W. Jr., Parrish M.D.. Graham T.P. Jr., et al.: Risk factors for infants undergoing aortic valvotomy for critical aortic stenosis in infancy. J. Am. Coil. Cardiol. 3:585, 1984. Fisher R.D., Mason D.T., Morrow A.G.: Results of operative treatment in congenital aortic stenosis. J. Thorac. Cardiovasc. Surg. 59218, 1970. Conkle D.M., Jones M., Morrow A.G.: Treatment of congenital aortic stenosis: An evaluation of the late results of aortic valvotomy. Arch. Surg. 107:649, 1973. Manouguian S., Seybold-Epting W.: Patch enlargement of the aortic valve ring by extending the aortic incision into the anterior mitral leaflet: New operative technique. J. Thorac. Cardiovasc. Surg. 78:402, 1979. Rastelli G.C., McGoon D.C., Ongley P.A., et al.: Surgical treatment of supravalvular aortic stenosis: Report of 16 cases and review of literature. J. Thorac. Cardiovasc. Surg. 51:873, 1966. Doty D.B., Polansky D.B., Jenson C.B.: Supravalvular aortic stenosis: Repair by extended aortoplasty. J. Thorac. Cardiovasc. Surg. 74:362, 1977. Ruckman R.N., Van Praagh P.: Anatomic types of congenital mitral stenosis: Report of 49 autopsy cases with consideration of diagnosis and surgical implications. Am. J. Cardiol. 42:592, 1978. Williams W.G., Pollock J.C., Geiss D.M., et al.: Experience with aortic and mitral valve replacement in children. J. Thoruc. Cardiovasc. Surg. 81:326. 1981. Nugent W.E., Freedom R.M., Nora J.J., et al.: Clinical course in pulmonary stenosis. Circulation 56(suppl. I):l-38, 1977. Watkins L.. Donahoo J.S., Harrinaton D., et al.: Surgical management of congenital pulmonary valve dysplasia. Ann. Thorac. &rg. 24498, 1977. Smallhorn J.F.. Sutherland G.R.. Tommasini G.. et al.: Assessment of total anomalous pulmonary venous connection by two-dimensional echocardiography. Br. Heart J. 46:613, 1981. Muller W.H.: The surgical treatment of transposition of the pulmonary veins. Ann. Surg. 134:683, 1951. Cooley D.A., Ochsner A.: Correction of total anomalous pulmonary venous drainage: Technical considerations. Surgery 42:1014, 1957. Katz N.M., Kirklin J.W., Pacific0 A.D.: Concepts and practices in surgery for total anomalous pulmonary venous connection. Ann. Thorac. Surg. 25:479, 1978. Stark J., de Leval M., Macartney F., et al.: Open heart surgery in the first SEPTEMBER

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