Bioresorbable vascular scaffold stents are improving rapidly but they are still associated with a higher risk of complications compared with drug-eluting metal stents, according to a meta-analysis of published studies presented at Cardiovascular Research Technologies 2016.

“Bioresorbable stents are clearly an attractive strategy, but our data suggest that physicians and patients should remain aware of the risks,” reported Dr. Alok Saurav of Creighton University Medical Center, Omaha, Neb.

The first bioresorbable vascular scaffold (BVS) device, Synergy, was approved this past October, but this stent, despite bioresorbable struts, still has body parts that are not fully bioresorbable. However, several fully bioresorbable devices have reached late stages of testing and may receive regulatory approval this year.

In the meta-analysis, eight studies – five randomized trials, two studies with propensity matching, and an observational study –the primary goal was to compare BVS to drug eluting metal (DEM) stents for definite stent thrombosis. Secondary outcomes included subacute stent thrombosis within 30 days and within 1 year and cardiac death, all-cause death, MI, and ischemia-driven target vessel revascularization (TVR).

Despite the fact that the mean age and gender distribution was the same when the 2,760 patients receiving BVS stents were compared to the 2,212 receiving DEM stents, and both received comparable antiplatelet regimens after the stent was placed, there was an 80% greater relative risk for definite stent thrombosis in the BVS group. Although this difference fell short of statistical significance (P = .06), Dr. Saurav called it a “strong trend.”

Several of the adverse events that were analyzed as secondary outcomes in this study were less frequent with the BVS, such as cardiac death (relative risk, 0.83) and all-cause death (RR, 0.74), but the statistics did not suggest a trend, so Dr. Saurav characterized these outcomes as similar. MI was an exception. This was more frequent in those received a BVS stent (RR, 1.35; P = .049), and this reached significance.

Most of the studies included in this analysis were conducted with the everolimus-eluting Absorb BVS device, which many are predicting will be the first fully bioresorbable stent to receive regulatory approval.

It is notable that another meta-analysis including some of the same studies and published just weeks prior to the CRT meeting drew the same conclusion about the increased risk of stent thrombosis with BVS relative to DEM stents ( Lancet 2016;387:537-44 ). This meta-analysis was restricted to six trials with 3,738 randomized patients. Unlike the meta-analysis presented at CRT, this study compared the two types of stents for both definite and probable stent thrombosis. For BVS relative to DEM stents, the relative risk for this outcome was 1.99 (P = .05).

“We think our restriction to definite stent thrombosis provides a stricter endpoint, but it’s notable that the results were relatively consistent,” Dr. Saurav reported.

Acknowledging that the increased risk of stent thrombosis appears to be modest for BVS relative to DEM stents, Dr. Saurav emphasized that these data should not discourage further development of bioresorbable stents, which are conceptually attractive.

“We cannot take these bioresorbable devices off the table,” he said. “But we do need more data to evaluate their risks relative to the conventional devices that are now available.”

The meeting was sponsored by the Cardiovascular Research Institute at Washington Hospital Center. Dr. Saurav reported no conflicts of interest.