NEW YORK - Restenosis rates are similar one year after implantation of an everolimus-eluting bioresorbable vascular scaffold or an everolimus-eluting metallic stent, but the scaffold has a higher risk of device thrombosis within 30 days, a new meta-analysis shows.
The meta-analysis suggests that the two interventions have a "similar requirement of repeat revascularization out to 1-year follow-up, despite inferior angiographic performance," first author Dr. Salvatore Cassese said by email.
This higher risk of stent thrombosis, twice as high with the bioresorbable device compared with the metallic stent after one year, "is somewhat surprising," said Dr. Cassese, of the Technical University of Munich's German Heart Center Munich. "The higher risk of scaffold thrombosis in relatively simple clinical (lesion) settings represents the new important finding showed by this meta-analysis."
A number of recently completed randomized trials showed comparable mid-term outcomes with the two devices, but data from routine clinical practice suggests a "somewhat higher rate of adverse events" with the bioresorbable scaffold, he said.
Most randomized trials comparing the two types of devices were small and not adequately powered to assess clinical endpoints, the authors noted. For their meta-analysis, they identified six trials involving 3,738 patients (mainly men, median age 62.3 years) that met their inclusion criteria (randomized design, an analysis by intention to treat, and a follow-up of at least six months).
The meta-analysis included 2,337 patients who received a bioresorbable scaffold and 1,401 who received a metallic stent. Median follow-up was 12 months.
Both groups had a 3% rate of target lesion revascularization, the primary efficacy outcome, the researchers noted in a report online November 16 in The Lancet.
The risk of the primary safety outcome, definite or probable stent/scaffold thrombosis, was significantly higher for those treated with a bioresorbable scaffold compared with those who received a metallic stent (1.3% versus 0.5%; odds ratio, 1.99), with the highest risk within 30 days after implantation.
In-device late lumen loss was also significantly greater in lesions treated with the bioresorbable device compared with the metallic stent.
Risk of myocardial infarction appeared to be higher in patients with the bioresorbable scaffolds than in those with metallic stents, but the difference was not statistically significant (5.2% versus 3.5%, p=0.06). The groups had similar rates of target lesion failure and risk of death.
The authors noted that their finding of at least similar efficacy of the bioresorbable scaffold versus the existing best-in-class drug-eluting stent at 12 months was achieved in a highly selected population that included mainly stable patients with single de-novo non-complex target lesions and excluded patients who had a higher risk for device failure.
Two large-scale randomized trials are under way that are expected to shed more light on the devices' relative efficacy in higher-risk populations.
Although the study's findings "should heighten concerns about the current generation of bioresorbable vascular scaffold technology, they should by no means be interpreted to mean that bioresorbable scaffolds are not worth pursuing," noted an editorial that accompanied the new meta-analysis. "Just as with first-generation drug-eluting stents, a complete understanding of the limitations of such technology is necessary before further advancements can be made."
"Little information appears available regarding the incidence of symptoms of angina in the comparison groups," Dr. Richard Chazal, who was not involved in the study, said in an email.
"This is important, as the principal utility of stents in stable patients is the relief of such symptoms," noted Dr. Chazal, president-elect of the American College of Cardiology and medical director of the Lee Memorial Health Systems' Heart and Vascular Institute in Fort Myers, Fla.
"Disappearing" bioresorbable scaffolds are viewed as a possible solution to potential problems of leaving metallic stents permanently inside a coronary vessel. These problems include impairing the function of the wall of the artery and limiting future options for treating the artery, especially with a bypass operation, explained Dr. Chazal.
Emergence of their anticipated benefit over metallic stents is expected several years after implantation, when elution of the anti-restenotic drug has stopped and the scaffold has dissolved.
"Longer-term follow-up will be needed to clarify whether these newer devices provide hoped-for advantages over metallic stents, or whether the early issues with thrombosis/clotting and vessel narrowing eventually results in more clinical problems," Dr. Chazal said.
The study had no funding source. Two of the 10 coauthors reported receiving fees from stent manufacturers or holding patents related to drug-eluting stent technologies, "outside the submitted work." A third coauthor is a member of the advisory board of Abbott, which includes a division that makes an everolimus-eluting bioresorbable vascular scaffold.