Fantom Bioresorbable Scaffold

Fantom Bioresorbable Scaffold


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VOL. 10, NO. 18, 2017


ISSN 1936-8798/$36.00


Fantom Bioresorbable Scaffold Verse, But Not Yet Chorus (An Incomplete Composition)* Stephen G. Ellis, MD


ith great excitement nearly a decade ago,

a current DES. Amplifying this problem is that the

a number of interventional thought and

scaffold also has a rectangular shape and excessive

industry leaders embraced the concept

height when compared with current DES, thus pro-

of a bioresorbable scaffold (BRS) in an attempt to

truding from the vessel wall and engendering blood

attenuate the truly long-term consequences of drug-

flow turbulence, with the result being a 2 risk of

eluting stent (DES) placement in coronary arteries,

device thrombosis versus DES during the first 6 to 12

namely an approximately 2% per year rate of target

months after implantation seen consistently in early

lesion failure extending beyond year 1, perhaps

studies. Post hoc analysis suggest that this problem

forever. This late risk was attributed to the perma-

can be ameliorated by high pressure and somewhat

nent presence of a metallic and often polymer “irri-

oversized balloon (1.1 to 1.25:1) post-dilation, but this

tant,” hence the thinking that if the device went

needs prospective confirmation (3,4).

away, so would the problem. Both polymer and

As the device begins to lose its structural rigidly

metallic devices were designed and tested, initially

after 6 to 12 months, the late risk phase ensues. Here,

limited by inflammation and poor vessel support,

if the device has not been well apposed to the vessel

but eventually evolving into devices that gained

wall at implantation (sometimes not so easy to tell

nearly world-wide regulatory approval.

with routine angiography), then without having been

However, close inspection of the results of current-

embraced by and healed into the vessel wall, it can

generation devices has raised legitimate concerns

collapse and draw endothelial and wall fragments

about their propensity toward thrombosis (1). Current

into the lumen (“dismantling”)—another stimulus for

thinking attributes this risk in the best studied device

thrombosis. Presumably, a better implantation tech-

by far, the Abbott Vascular Absorb scaffold (BVS)

nique will alleviate this problem, too, but the only

(Abbott Vascular, Santa Clara, California), to both the

studies for which we have long-term follow-up in

device itself and how it has been implanted (2).

sizable numbers of patients were performed before

There appear to be 2 phases of risk: early in small

these implantation issues were understood.

vessels and later in large vessels. Due to its sizeable

Beyond this, of course, is the fact that the “value

strut width (2 strut size compared with metallic

proposition” of the entire concept—that patients will

stents in order to match their radial strength), the

see better outcomes after the device resorbs (w3

scaffold acts more like a snowshoe than a cross

years for the Absorb scaffold)—has really yet to be

country ski on soft snow and typically poorly “scores”

tested, because so few patients have been followed in

and embeds into the vessel wall when implanted like

controlled comparative studies beyond 3 years. SEE PAGE 1832

In this issue of JACC: Cardiovascular Interventions, *Editorials published in JACC: Cardiovascular Interventions reflect the

we now have a report of a carefully performed study

views of the authors and do not necessarily represent the views of JACC:

with a newer BRS, the Fantom device (REVA Medical,

Cardiovascular Interventions or the American College of Cardiology. From the Department of Cardiovascular Medicine, Cleveland Clinic, Cleveland, Ohio. Dr. Ellis has been a consultant for Abbott Vascular,

San Diego, California), from Cohort A of the Fantom II (Safety & Performance Study of the FANTOM Siroli-

Boston Scientific, and Medtronic; and has received research funding from

mus-Eluting Bioresorbable Coronary Scaffold) study

Abbott Vascular and Boston Scientific.

(5). This device is made from a different polymer than




Fantom BRS: Verse, But Not Yet Chorus

the Absorb BVS (a polycarbonate copolymer of tyro-

reassuring. Recall that provision of mean and SD of

sine analogs vs. PLLA), has somewhat thinner but still

late loss really doesn’t tell the whole story, how-

rectangular struts (125 m m vs. 157 m m), reabsorbs over

ever, because clinical restenosis only occurs at the

1.5 to 2 years and elutes sirolimus instead of ever-

far “tail” of the late loss cumulative distribution

olimus. Unlike some BRS, it does not require refrig-

curve, when late loss exceeds about 1 mm. No such

eration, and unlike the Absorb BVS, it can be

curve was provided. However, the binary restenosis

expanded above nominal size by 0.75 to 1.0 mm

rate of 2% suggests this should not be a problem, at

without risk of fracture. In the Fantom I study, 7 pa-

least in the type of patients studied. Regarding the

tients underwent device delivery and were followed

failure to deliver patients, 4 of 121 sounds a bit

with intravascular ultrasound and optical coherence

high, but without provision of details, it’s hard to

tomography for 4 months with satisfactory results (6).

know what to conclude.

The Fantom II study’s focus was principally on effi-

Of course, given the history of BRS before it, the

cacy at 6 months as assessed by quantitative coronary

real question is one of safety over time. The thinner

angiography–determined late loss in 117 patients with

struts than the Absorb device, fairly aggressive use of

relatively simple anatomy and clinical presentation

post-dilatation, frequent use of intravascular imaging

(typical for early DES studies.) The rate of major

and reabsorption within 2 years provides hope that

adverse cardiovascular events was also evaluated,

the risk of device thrombosis may be acceptable. With

but the study really wasn’t well-powered to assess

9-month follow-up, Cohort B will provide some

this unless the results were awful.

information, but will hardly be definitive.

From this study, Abizaid et al. (5) report apparently

In short, these results should provide impetus for a

encouraging results: using a technique characterized

larger and more definitive study. In the meanwhile,

by relatively frequent post-dilatation (76%, with a 10%

the 1 year ABSORB IV study results will likely either

oversized balloon at a mean pressure of 16.6 atm) and

provide a death knell or new life for that device,

nearly uniform use of intravascular imaging, in-device

and perhaps the long term findings from earlier

late loss of 0.25  0.40 mm with 85% angiographic

ABSORB trials (II, III, Japan, and China) will tell us if

follow-up, major adverse cardiovascular events in

the long-term value proposition of BRS remains worth

2.9% and scaffold thrombosis in 0.9% of patients.


There were also 4 device delivery failures (3.3%). What should we make of these results?


Sirolimus has proven to be an effective anti-

Ellis, Cleveland Clinic, Department of Cardiovascular

restenosis agent when given in an appropriate

Medicine, Desk J2-3, 9500 Euclid Avenue, Cleveland, Ohio

dose, so the efficacy results are as expected, but

44195-0001. E-mail: [email protected]

REFERENCES 1. Stone GW, Gao R, Kimura T, et al. 1-year outcomes with the absorb bioresorbable scaffold in patients with coronary artery disease: A patientlevel, pooled meta-analysis. Lancet 2016;387: 1277–89. 2. Colombo A, Ruparelia N. Who is thrombogenic: the scaffold or the doctor? Back to the future! J Am Coll Cardiol Intv 2016;9:25–7. 3. Arroyo D, Cook S, Puricel S. Mechanisms of late and very late bioresorbable vascular scaffold

thrombosis: is it only about flow? J Am Coll Cardiol 2016;67:1259–60.

the FANTOM II study. J Am Coll Cardiol Intv 2017;10: 1832–8.

4. Ellis SG, Gori T, Steffenino G, et al. Clinical, angiographic and procedural correlates of Absorb scaffold thrombosis: a matched multicenter registry analysis (abstr). J Am Coll Cardiol 2017;69

6. de Ribamar Costa J, Abizaid A, Chamie D, Lansky A, Kochman J, Koltowski L. Initial results of the FANTOM 1 trial: a first-in-man evaluation of a novel, radiopaque sirolimus-eluting bioresorbable vascular


scaffold (abstr). J Am Coll Cardiol 2016;67 Suppl:232.

5. Abizaid A, Carrié D, Frey N, et al. 6-month clinical and angiographic outcomes of a novel radiopaque sirolimus-eluting bioresorbable vascular scaffold:

KEY WORDS bioresorbable stent(s), scaffold, stent, thrombosis