PARIS, FRANCE — Although unlikely to quell the continuing controversy, extended follow-up from two trials shows just one case of late scaffold thrombosis between 2 and 3 years in select patients implanted with the Absorb bioresorbable vascular scaffold (BVS) (Abbott Vascular)[1,2].
The single case occurred in ABSORB JAPAN on day 810 in a patient who had severe restenosis even after thrombectomy and ballooning and was not on dual antiplatelet therapy (DAPT) at the time of the event, only aspirin, Dr Ken Kozuma (Teikyo University Hospital, Tokyo, Japan) said.
No events occurred between 2 and 3 years in patients treated with the metallic everolimus-eluting stent (Xience, Abbott Vascular), resulting in an overall rate of definite/probable scaffold thrombosis at 3 years of 3.6% for Absorb BVS and 1.6% for Xience.
The 3-year rate of definite/probable scaffold thrombosis was exceedingly low in the second study, ABSORB CHINA, at 0.8% (two events) with Absorb BVS and 0% with Xience, with no new events between 2 and 3 years with either device.
The findings were reported here at a late-breaking trials session at EuroPCR 2017 along with less flattering 12-month data from several European registries, including the Swedish SCAAR and German-Austrian GABI registries showing increased stent thrombosis with the BVS.
Abbott recently advised physicians in Europe that starting May 31, the Absorb and Absorb GT1 BVS systems can be used only in the clinical registry setting at select sites/institutions that will be monitoring the technology until summer 2018.
Based on surprising 2-year results from ABSORB 3 trial showing a significant increase in target lesion failure with the BVS, the FDA announced in March it was investigating the Absorb device and cautioned physicians regarding its use in smaller coronary vessels. Recent data have shown that scaffold thrombosis is reduced with the use of the preparation, sizing, and postdilation (PSP) protocol.
Following the presentation of the new Absorb data, panelist Dr Vinay Bahl (All India Institute of Medical Sciences, New Delhi) said, “It’s good to have long-term data from as many studies as possible because of the concerns raised, but I don’t think we have yet to figure out why there is a difference between the studies from China and Japan as compared with the Absorb studies from the US.”
He said in addition to implantation technique, the “other factor I personally think is important is the continuation of DAPT, because in this part of the world, like in India, most of the patients continue to have clopidogrel because it’s really cheap and the patients are relatively younger, so the bleeding risks are not that high. In both of these studies, 50% of patients were on DAPT as compared with the US studies where it was stopped after 12 months.”
When session chair Dr Ron Waksman (MedStart Heart and Vascular Institute, Washington, DC) polled the audience as to how many would prescribe clopidogrel for 3 years in an Absorb patient, however, less than half raised their hands.
The ABSORB JAPAN protocol called for 1 year of DAPT, but Kozuma said they currently recommend DAPT for 3 or 4 years. He suggested that several factors played a role in scaffold thrombosis, most notably a sizing mismatch, which occurred in three patients with large vessels implanted with smaller scaffolds.
Between 2 and 3 years, the rate of target lesion failure, a composite end point of cardiac death, target vessel MI, and ischemia-driven target lesion revascularization, was 1.6% in both arms. The 3-year target lesion failure rate was 8.9% for Absorb and 5.5% for Xience.
Angiographic late lumen loss at 3 years was within a clinically acceptable range (<0.4 mm) and consistent with that observed in the ABSORB Cohort B study, Kozuma said.
ABSORB CHINA
In ABSORB CHINA, the rate of target lesion failure was 1.3% with Absorb and 0% with Xience between 2 and 3 years, and 5.5% vs 4.7% at 3 years.
Rates were not statistically different between the Absorb and Xience arms for target vessel MI (2.5% vs 0.9%) or ischemia-driven target lesion revascularization (4.2% vs 2.6%).
Dr Davide Capodanno (University of Catania, Italy), who chaired a press conference highlighting the studies, pointed out that ABSORB CHINA has always been an outlier compared with other BVS trials and questioned what may have contributed to the positive findings.
ABSORB CHINA study author Dr Runlin Gao (Fu Wai Hospital, Beijing, China) responded that less than 10% of implantations were in vessels smaller than 2.25 mm.
“The ABSORB CHINA trial selected relatively larger vessels; the mean reference vessel diameter was 2.81 mm, and in other trials such as ABSORB Japan, ABSORB II, or ABSORB 3, the reference vessel diameter was around 2.6 mm or 2.7 mm,” he said. “Another thing is that only 9.2% of patients who received BVS had a vessel diameter less than 2.25 mm” compared with about 15% of patients in other trials.
Given that the Absorb BVS has a relatively thick strut, about 157 µm, implanting in too small a vessel “would result in some problems,” he added.
Gao also noted that almost all patients underwent predilation, postdilation was performed in 63% of BVS patients, and 20% of patients remained on DAPT at 3 years.
Dr Robert de Winter (Academic Medical Center, Amsterdam, the Netherlands), who recently published 2-year data from the AIDA trial showing an increased risk of scaffold thrombosis and target vessel MI with Absorb BVS, commented during the press conference that appropriate sizing may be the most important factor in the PSP protocol.
“We’ve done a preliminary PSP analysis as well, and I tend to agree that sizing may be more important than postdilation,” he said.
ABSORB CHINA and ABSORB JAPAN were sponsored by Abbott Vascular. Gao reported no relevant financial relationships. Kozuma reports honoraria from Abbott Vascular and Terumo and institutional grant/research support from Abbott Vascular and Boston Scientific.
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