Bioresorbable vascular scaffolds represent the next revolution in stent technology. They serve the dual purpose of antiproliferative drug delivery to vascular lumen like a drug-eluting stents (DES) as well as phased strut resorption over time leading to virtual elimination of stent thrombosis. The ABSORB GT-1 stent was the prototype bioresrbable vascular scaffold with maximum clinical experience and initial promising results. However, reports of stent thrombosis emerged with ABSORB too. Although the use of intracoronary imaging and proper implantation technique has the potential to reduce stent thrombosis rates, the device has been withdrawn from the market for now. We report a case of late stent thrombosis with ABSORB which was managed with DES-supported intracoronary imaging.
How to cite this article: Pradhan A, Vishwakarma P, Vankar S, Sethi R. “The unpredictable ABSORB” – very late stent thrombosis of bioresorbable vascular scaffold. Heart Views 2019;20:65-9
How to cite this URL: Pradhan A, Vishwakarma P, Vankar S, Sethi R. “The unpredictable ABSORB” – very late stent thrombosis of bioresorbable vascular scaffold. Heart Views [serial online] 2019 [cited 2023 Mar 29];20:65-9. Available from: https://www.heartviews.org/text.asp?2019/20/2/65/263847
Bioresorbable vascular scaffolds (BRS) represent a significant evolution in stent technology. They offer a multitude potential advantages over their metallic congeners including full restoration of vessel vasomotion, obviation of the need for prolonged dual antiplatelet therapy (DAPT), prevention of potentially deleterious effects of long-term metals' presence, and possibility of future graft insertion to name a few.,,
ABSORB (polymer-based BRS) is the most widely implanted BRS to date with the largest clinical data and experience. After initial enthusiasm from the success of ABSORB I and II studies, reports of late scaffold thrombosis in ABSORB III study have given way to circumspect and suspicion over long-term advantages of ABSORB as well as bioresorbable stent technology.,
We report a case of late stent thrombosis (ST) of ABSORB presenting as ST segment elevation myocardial infarction.
A 30-year-male was admitted in the coronary care unit with a history of acute onset of severe chest pain lasting for 3 h. His electrocardiogram revealed normal sinus rhythm and ST segment elevation in anterior precordial chest leads with maximum elevation of 7 mm seen in lead V3. He was an active smoker and chewed tobacco. He had suffered from anterior wall myocardial infarction (MI) 1½ year ago and had underwent percutaneous coronary intervention (PCI) with stenting to left anterior descending (LAD) with BRS-ABSORB (Abbot Vascular Inc.,) with size of 3.5 mm × 23 mm.
The patient received DAPT (aspirin 150 mg and clopidogrel 75 mg) which he took regularly for 1 year. After 1 year of DAPT, the patient was continued with aspirin 150 mg only. Along with this, he was also prescribed beta-blocker, angiotensin-converting enzyme inhibitor, spironolactone, and low-dose diuretic. However, he had defaulted on all the medications for the past 4 months.
The patient was thrombolysed with intravenous streptokinase within the window period of 3 h. He was taken for routine angiograpghy within 24 h, as a part of pharmacoinvasive therapy.
The coronary angiogram revealed severe in-stent disease in the mid portion of LAD coronary artery [Figure 1] and [Video 1]. The two radiopaque markers of ABSORB were clearly delineated [Figure 2].
Figure 1: Coronary angiogram in posteroanterior view with cranial angulation showing discrete lesion in mid part of the left anterior descending artery (arrow)
The left main coronary artery was engaged with Extra Back Up guide catheter (Medtronic Inc., Minneapolis, MN, USA) and LAD was wired with Runthrough NS (Terumo Inc., Somerset, NJ, USA) wire. Intravascular ultrasound (IVUS) was performed with Eagle eye catheter, 6F (Volcano Inc., North Ryde, NSW, NZ). The malapposed and undersized ABSORB stent was visible with the presence of intraluminal thrombus [Figure 3] and [Video 2]. Plaque extending proximal to stent was also visualized in IVUS run indicating probably a geographical miss. The lesion was predilated with a 2.5 mm × 12 mm semicompliant balloon. A 3.5 mm × 28 mm metallic drug-eluting stent (DES) (Xience Prime, Abbot Vascular Inc., Santa Clara, CA, USA) was implanted in the LAD. The stent was postdilated with a 3.5 mm × 12 mm noncomplaint balloon at high pressures, and a final IVUS run revealed a fully apposed stent without any plaque prolapse, edge dissection, or residual thrombus [Figure 4] and [Video 3]. Two layers of stent were visible, the outer one being previously implanted ABSORB and the inner one being metallic DES [Figure 5] and [Video 4]. Prasugrel and aspirin were initiated, and the importance of drug compliance was reemphasized. He was discharged the next day and was asymptomatic as of 3-month follow-up.
Figure 3: Left panel - gray scale intravascular ultrasound image in the left anterior descending demonstrating the malapposed and undersized ABSORB bioresorbable vascular scaffolds (arrow) with intraluminal thrombus (*)- Right panel - gray scale intravascular ultrasound image proximal to ABSORB showing plaque burden indicating geographical miss
Figure 5: Final intravascular ultrasound image of left anterior descending showing two layers of stent in the left anterior descending - the inner circle depicting apposed and expanded metallic drug-eluting stents (red arrow) and the outer circleb representing unresorbed bioresorbable vascular scaffolds (9 o'clock to 12 o'clock, white arrow)
Contemporary DES have shown improved outcomes following PCI owing to diminished rate of both ST and restenosis. However, the long-term persistence of metal in the coronary vasculature has the potential for inflammation, restenosis, and neoatherosclerosis. BRS were introduced to overcome many of the limitations of a metallic drug eluting stent (DES). BRS serves the dual purpose of drug elution like a DES as well as late benefits of dissolution of stent. There are a multitude of advantages of disappearance of a stent including the potential for reintervention, restoration of vasomotion, better imaging of stented segment, obviation of side branch occlusion by stent struts, future vessel growth, and of course, alleviating the need for long-term antiplatelet therapy., Because of the potential for complete disappearance of stent material, there was associated anticipation of complete alleviation of risk for ST.
The ABSORB GT-1 remains the prototype BVS with maximal clinical experience. It consists of a fully resorbable poly–L-lactide scaffold with fully resorbable poly D, L-lactide-based coating of everolimus. The BRS resorption by remodelling is complete by 3 years and can continue up to 5 years.
The initial positive results of ABSORB cohort A and B led to randomized ABSORB II and III randomized trials. Both the studies met their primary end points and established that ABSORB is noninferior to metallic DES with respect to target lesion failure. BVS-EXAMINATION and ABSORB-TROFI II studies also demonstrated safety and feasibility of ABSORB in acute MI while the later study demonstrated better healing in the ABSORB arm on follow-up by intracoronary imaging.,
However, despite the anticipation and initial enthusiasm, reports of scaffold thrombosis emerged with ABSORB too. The rate of subacute or probable scaffold thrombosis was higher with ABSORB vis-à-vis metallic DES. The incidence was from 0.42% to 1.37% with the highest rates seen in patients of ACS (1.42%).
The various causes of early scaffold thrombosis included malapposition, underdeployment of scaffold, incomplete coverage of lesions, acute disruption, and overlap. On the other hand, malapposition, peri-strut low-intensity area, late discontinuity, underdeployed stent, uncovered struts, and neoatherosclerosis were responsible for late scaffold thrombosis. More recently, a “PSP” (predilatation, correct scaffold sizing, and postdilatation) algorithm for scaffold deployment has been proposed to improve outcomes after BRS implantation.
The thicker struts (150–160 μm with ABSORB vs. 50–60 μm with new generation metallic DES) of ABSORB may have led to flow disturbances and delayed neointimal coverage leading to scaffold thrombosis. At present, Abbott Vascular has withdrawn ABSORB from commercial use due to low demand but follow-ups would continue.
With regard to ST, there is always the rhetorical question, who is at fault – the patient, the stent, or the operator?, In our case, probably all three. The patient erred by virtue of his discontinuation of his antiplatelet medications. The operator probably not only by lack optimization of the ABSORB by imaging guidance but also by failure of application of “PSP” technique as discussed above. The device by its inherent bulky design and slow rate of dissolution was also in cahoots with other factors. Compared with metallic DES, the risk of ST with ABSORB has shown to be increased by two times. Moreover, the risk continues to remain high at all time points – early, late, and very late.
The lessons learnt with ABSORB BRS can be utilized to guide and modify evolving BRS technologies like MAGMARIS (Biotronik Inc., Switzerland) and MeRES-100 (Meril Life Sciences, India).
BVS represented a remarkable evolution in stent technology with a multitude of potential benefits. ABSORB GT-1 was the prototype and clinically approved BVS with maximum clinical data. However, despite a host of potential benefits late ST has remained its bane. Proper implantation technique under intracoronary imaging guidance and appropriate sizing of device has been postulated to ameliorate some of the adverse outcomes. The experiences with ABSORB BRS will have potential implication for future BRS technology.
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