Meta-Analysis Echoes Late Safety Concerns With Bioabsorbable Scaffold

Patrice Wendling

January 17, 2017

KYOTO, JAPAN — The risk of stent/scaffold thrombosis (ST) was higher through 2 years of follow-up with the Absorb GT1 bioabsorbable vascular scaffold (BVS) (Abbott Vascular) compared with everolimus-eluting stents (EES) in a new meta-analysis[1].

The rate of target lesion failure (TLF), defined as a composite of MI and cardiac death, however, was similar between the two devices.

"When considering BVS implantation, patients should be appropriately informed about the reported thrombotic risk of BVS until complete scaffold resorption," lead author Dr Toshiaki Toyota (Kyoto University, Japan) told heartwire from Medscape.

The meta-analysis includes ABSORB II but not the recently updated bombshell 3-year outcomes from ABSORB II, in which Absorb GT1 BVS was also associated with increased ST and did not improve vasomotor reactivity compared with the Xience EES metallic stent (Abbott Vascular).

"Considering the different degree of BVS resorption process between within 2 years and beyond 2 years after BVS implantation, especially for the lesions without intimal coverage on the BVS struts, the results should be separately interpreted," Toyota said. "We need longer follow-up data, such as 5 years and more, to understand the true effect of BVS relative to EES."

Prior meta-analyses of randomized controlled trials have shown that the BVS is associated with similar risk for TLF, but a higher risk for ST at 1 year.

The present meta-analysis, published January 9, 2017 in JACC: Cardiovascular Interventions, is the first to examine the risk of very late ST (VLST) beyond 1 year.

It comprised 2 years of follow-up data from 2567 patients treated with BVS and 19,806 treated with EES in three randomized trials, four comparative observational studies, and 17 single-arm studies. The brand of EES was not limited in the meta-analysis; however, most included studies used Xience series, and three single-arm studies used Boston Scientific's PROMUS or PROMUS Element.

Among the seven comparative studies, the risk for VLST trended higher for BVS than for EES between years 1 and 2 (odds ratio 2.03, 95% CI 0.62–6.71) and was significantly higher for BVS through the entire 2 years follow-up (OR 2.08, 95% CI 1.02–4.26).

When all 24 studies were included, the pooled incidence rates of ST and VLST were significantly higher in the BVS group than in the EES group between 1 and 2 years (0.24% vs 0.003%) and through 2 years (1.41% vs 0.56%).

"Persistent strut malapposition of the scaffold might be an important mechanism of BVS very late stent thrombosis. Thus, appropriate device sizing and meticulous implantation technique using optical coherence tomography guidance would be crucial for the Absorb GT1 BVS," Toyota said.

Notably, pooled incidence rates of TLF were comparable for BVS and EES between years 1 and 2 (1.88% vs 1.78%) and through 2 years follow-up (7.90% vs 7.49%).

TLF risk in the seven comparative studies was also similar for the two devices between 1 and 2 years (OR 1.40, 95% CI 0.65–3.01) and through 2 years (OR 1.08, 95% CI 0.76–1.54).

Toyota observed that cardiac death and MI were relatively low-frequency events in the contemporary PCI studies and that it's "possible the single-arm studies of EES included more complex patients and lesions than those of BVS, which led to a higher rate of target lesion revascularization/target vessel revascularization, offsetting the effect of lower rates of ST."

He said the study was limited by insufficient 2-year outcomes reports from randomized trials comparing BVS with EES and the relatively small number of patients with BVS VLST events, which made it difficult to estimate the rate of BVS VLST accurately.

Drs Fernando Alfonso and Javier Cuesta (Hospital Universitario de La Princesa, Madrid, Spain) note in an accompanying editorial[2] the study also did not analyze important angiographic efficacy outcome measures. "This issue remains of major relevance, as some previous studies with mandated invasive surveillance suggested that classic angiographic surrounding end points, including acute lumen gain, late lumen loss, and other late angiographic parameters, may be slightly but significantly poorer with BVS compared with EES."

The editorialists agree patients should be informed of the risk for ST and VLST until complete BVS resorption but write that newer-generation polymeric BVS with thinner struts and a more flexible platform might overcome most of the limitations encountered with the first-generation BVS.

They add, "However, we should learn our lessons and maintain close critical scrutiny on the clinical performance of these novel devices. Science and, more important, responsible patient care should be based on more than expectations."

Toyota reported no relevant financial relationships. Disclosures for the coauthors are listed in the paper. Alfonso and Cuesta reported no relevant financial relationships.

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