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The Absorb bioresorbable vascular scaffold (BVS) continues to be dogged by stubbornly high rates of device thrombosis at 2 years, both a meta-analysis and a European registry showed.

In the meta-analysis, the BVS was associated with a greater risk of target lesion failure (9.6% versus 7.2%, RR 1.32, 95% CI 1.10-1.59) and stent thrombosis (2.4% versus 0.7%, RR 3.15, 95% CI 1.87-5.30) when compared with metallic everolimus-eluting stents (EES).

In particular, , even in the very late period beyond 1 year of device placement (RR 3.96, 95% CI 1.47-10.66), according to George D. Dangas, MD, PhD, of Icahn School of Medicine at Mount Sinai in New York City, and colleagues.

There was no difference in all-cause or cardiovascular deaths between groups, they wrote in the Journal of the American College of Cardiology (JACC).

The pooled analysis by Dangas' group included seven trials that randomized patients to BVS (n=3,261) or metallic EES (n=2,322). The Xience stent constituted 96.6% of EES devices used, with the remaining few being the Promus Element. Median follow-up was 2 years.

Notably, Dangas' group included the recent AIDA trial that pushed out early preliminary results on the recommendation of its Data Safety Monitoring Board due to safety concerns. In this trial, most patients got pre-dilation and post-dilation, putting pressure on the idea that bad implantation technique was to blame for stent thrombosis.

Even experienced German operators that stuck to best practices also observed higher-than-expected adverse event rates after BVS implantation, a separate study found.

Combined death, MI, and target lesion revascularization rates in the ISAR-ABSORB Registry, according to Robert A. Byrne, MB BCh, PhD, of Deutsches Herzzentrum München in Germany, and colleagues. In JACC: Cardiovascular Interventions, the authors broke this down by individual endpoint:

• Death: 6.3%
• MI: 3.9%
• Target lesion revascularization: 16.0%

There was a 4.2% rate of definite or probable scaffold thrombosis at the 2-year mark (3.8% when only counting definite cases).

"Despite a high rate of pre-dilatation (97.7%), a rate of post-dilatation comparable with or higher than those in randomized trials, and good acute procedural results, rates of adverse events are numerically higher in our report," the authors noted.

Of the four patients who had definite stent thrombosis between years 1 and 2, " only 1 was on dual antiplatelet therapy (DAPT), 1 patient had post-dilatation, and interestingly all 4 had 3.0-mm or 3.5-mm stents," E. Murat Tuzcu, MD, and Samir Kapadia, MD, both of the Cleveland Clinic, pointed out in an accompanying editorial.

"The present study is the first report of long-term clinical outcomes among patients undergoing [BVS] implantation during routine clinical practice. Event rates were higher than expected, possibly explained in part by a less favorable cardiovascular risk profile and lesion characteristics, in addition to the effect of very early clinical experience with the device," Byrne's group concluded.

They cited a patient population (419 consecutive participants enrolled at two high-volume Germany centers) with 31.5% diabetes and 38.9% acute coronary syndrome in the registry. Half of lesions treated were complex, they added.

"Considering the facts that there is no proven benefit, the theoretical advantages are promissory, and safety concerns raised by recent reports, the most prudent approach appears to be using the Absorb BVS only within the context of research studies with careful follow-up and data collection," Tuzcu and Kapadia maintained.

This is certainly the case in Europe, where regulators have restricted the use of Absorb to centers participating in registries. In the U.S., the device was the subject of a FDA safety alert earlier this year on the basis of high 2-year event rates observed in the ABSORB III trial.

"Hospitals, physicians, and patients should carefully weigh whether the increased procedural duration, complexity, and cost of the BVS, with likely a need for prolonged DAPT, are worth the theoretical, though appealing, long-term potential of a coronary artery returning to its native state," urged Sripal Bangalore, MD, of New York University School of Medicine in New York City, and colleagues.

In their editorial, they declared it "time to increase our sophisticated clinical trials and spur greater investment in nonclinical studies and design refinement such that we allow a potential promise to play out before being accepted without question or rejected prematurely."

The meta-analysis by Dangas' group suffered from differences in trial design -- including inclusion/exclusion criteria and endpoint definitions -- among the studies included. On the other hand, the ISAR-ABSORB Registry study by Byrne's group was limited by having just two participating centers and a relatively small sample size.