HRO~03OSIS RESEARCH Printed in the United States
VASCULAR INJURY AND THROMBOSIS :
e_oamon Press, T--c .
A SCANNING ELECTRON MICROSCOPIC STUDY
G .E . Stoner, and G .M . Chisolm, Department of Material Sciences, University of Virginia, Charlottesville, Va . 22901 S . Srinivasan, T .R . Lucas, and P .N . Sawyer Electrochemical and Biophysical Laboratories, Department of Surgery, State University of New York Downstate Medical Center, Brooklyn, New York 11203
(Received 16 .11 .1973 ; in revised form Accepted by Editor A .L . Copley)
ABSTRACT Injury to the blood vessel wall and atherosclerosis enhance the possibility of thrombus depostion . A knowledge of the changes in vascular morphology and the extent of thrombus deposition produced by injury is essential in elucidating the mechanism of this reaction . In the present work, scanning electron microscopic technique was used to examine the canine blood vessel wall at or near a site of injury caused by vascular clamping . Proximal to the clamping, the endothelial folds in normal vessels are clearly visible . The intima is completely severed at the site of clamping . At a distance of lmm distal to the injury, the vascular wall is completely covered with a layer of thrombi, composed mainly of platelets, fibrin and trapped erythrocytes . Thus, injury to the blood vessel wall destroys the endothelial structure and triggers thrombus deposition .
INTRODUCTION A knowledge of the three dimensional structure of the blood vessel wall under normal and abnormal conditions is essential in characterizing changes in vascular morphology and understanding the extent and nature of thrombosis brought about by injury and disease . The ability of the healthy intima to prevent thrombus deposition is a poorly understood process
1-3 , which is
disrupted by injury and vascular diseases like atherosclerosis . The purpose of this initial study, is to examine the endothelium near a limited vascular injury using a scanning electron microscope (SEM) . 699
VASCULAR INJURY e, Tim0~LFOSIg
METHODOFPROCEDURE A young 7 Kg dog was anesthetized with an intravenous dose of sodium pentabarbital (approximately 25 mg/kilogram body weight) . Approximately 6cm of the left femoral artery was exposed and clamped with a hemostat for sixty seconds . The clamp was released allowing normal blood flow . The chest of the animal was opened and the pericardial membrane was cut . About 200 ml of isotonic saline was then injected slowly into the left heart and the right heart was pierced to allow blood to flow out . In this manner, the vascular tree was hemodiluted to clear most of the blood . Following this, the left heart was similarly perfused with diluted formalin to initiate tissue fixation in vivo .
Following death the 6cm segment of the left femoral artery, 3 cm
proximal and 3 cm distal to the hemostat injured area, was removed and placed in 10% formalin-in-saline for 24 hours final fixation . The vessel was then removed, dried, mounted and coated with gold for SEM observation in a manner described elsewhere 4,5 . RESULTS AND DISCUSSION
Proximal to the clamping of the artery the normal . femoral endothelium is seen in Figure 1 .
Fig . 1 : Endothelial folds of left femoral artery at a distance of 1 millimeter proximal to injury (850X) .
NJCRY & _1- OQ,,BO :SIS
ridges first observed in SEM and labeled "endothelial
folds" 7-13 are characteristic of by Shimamoto 6 and later corroborated by others arteries and vena cava of all mammalian species observed to date (rabbits, monkeys, humans, dogs, rats, and guinea pigs) . It is also interesting to note that the width and length of those folds (approximately 15-17M) was found to be approximately the same among the species . The site of clamping with the hemostat is shown in Figures 2a and b .
Left femoral artery at site of hemostat-induced injury (130X) .
As can be seen, the intima is completely severed along both outer edges of the clamp exposing subendothelial tissue . Figure 2(b) shows that the extent of the injury is probably restricted to the intima endothelium . Figures 3(a) and (b) show the wall at a distance of one millimeter distal to the injury (as compared to Figure 1 which is one millimeter proximal) . Here, the wall is almost_ completely covered with a layer of thrombus composed mainly of platelet, fibrin strands and RBCs aggregates adhering to the vessel wall . It is
VASCULAR INJURY & TFUROMCBOSIS
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Fig . 2(b) :
Left femoral artery at site of hemostat-induced injury (850X) .
Fig . 3(a) :
Platelet thrombi adhering to endothelium at a distance of one millimeter distal to injury (700X) .
V_a 3 CCLAR INJURY THRO [BOSI3
adhering to endothelium at a distance of one
millimeter distal to injury (2800x) .
of particular interest to observe the one "clean" portion in the figure . This little "island" of endothelium was the only such area in the vicinity of 0-1 centimeter distal to the injury . (In Figure 4, at 2 cm, distal, the entire vessel is again completely normal) . This seems to indicate that alteration in vascular homeostasis which allows platelets to adhere to the wall, did not take place in this little isolated area near the injury . The fact that this area is exposed to the same tissue-activated platelets and the same blood flow patterns as the surrounding platelet-covered area indicates, perhaps, that there is still normal homeostasis . That is, the interfacial process during homeostasis are still occurring in this region . In similar experiments, the effect of more severe injury on the surface charge of the vessel wall was determined using streaming potential techniques . When injury was induced (again by hemostat clamping) the amount of charge of the blood vessel wall became less negative as the extent of injury was increased . This experiment, therefore, is consistent with the hypothesis that negative surface charge and vascular homeostasis are directly related and that injury and/or vascular disease destroy the processes necessary to maintain this charge 14-19
Fig . 4 :
VASCULAR INJURY & THROMBOSIS
Normal endothelial folds two centimeters distal
to injury (750X) .
It is proposed to continue these studies in essentially two directions . The first will be to measure the effects of anticoagulant, vasoactive and antiatherosclerotic drugs, on the healing of vessels which have been injured and/or endarterectomized . Secondly, it would seem meaningful to work on an improved procedure (and/or device) for vascular clamping to minimize injury to the blood vessel wall during surgery . ACKNOWLEDGEMENTS The authors would like to thank Drs . F . Attinger and A . Navarro, Department of Biomedical Engineering, University of Virginia, for surgical assistance in this study . REFERENCES 1 .
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VASCULAR INJURY & THROMBOSIS
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VASCULAR INJURY & THROMBOSIS
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Vo1 .4,No .5
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