‘Reassuring’ 18-Month Results Seen With Absorb BVS, but Longer-Term Follow-up Still Needed

Mid- and longer-term follow-up results from a single center implanting the Absorb bioresorbable vascular scaffold (BVS) suggest the novel device is associated with an “acceptable” rate of major adverse cardiovascular events, with rates comparable to contemporary second-generation drug-eluting stents, according to investigators.

Additionally, there were no reported cases of early scaffold thrombosis in this “complex, real-world population” treated with Absorb BVS (Abbott Vascular).

Published online July 27, 2016, in JACC: Cardiovascular Interventions, the study, led by Cordula Felix, MD (Erasmus Medical Center, Rotterdam, the Netherlands), included 249 patients enrolled as part of the BVS Expand registry, although five patients were excluded from the per-treatment analysis because the device could not be successfully implanted.

By 1 year, MACE, a composite of cardiac mortality, MI, and target lesion revascularization, had occurred in 5.1% of the 244 treated patients. Using Kaplan-Meier estimates, the MACE rate at 18 months was 6.8%, driven primarily by MI. At 18 months, the individual rates of cardiac death, MI, and target lesion revascularization were 1.8%, 5.2%, and 4.0%, respectively.

Rates of scaffold thrombosis overall and of definite cases were 2.7% and 1.9% at 18 months, respectively. There were no reported cases of acute, subacute, or very late thrombosis. In univariate analysis, the researchers were unable due to lack of statistical power to identify any significant predictors of scaffold thrombosis, but there was a trend toward higher rates among older patients, those with long or calcified lesions, and those with small vessels (reference vessel diameter < 2.5 mm).

Based on the findings, investigators say the results “support the potential use of [Absorb] BVS for complex lesions.” 

Tommaso Gori, MD (University Medical Center, Mainz, Germany), who was not involved in the analysis, told TCTMD the rate of stent thrombosis—whether it is defined as definite, probable, or possible—is declining compared with earlier reports. In 2011, when some of the first European centers began reporting on the device, there was a lack of protocol in terms of implantation. Since then, however, there is growing awareness regarding the technical properties of the stent and the need for adopting implantation protocols.

For example, at his center, the Absorb-specific strategy includes predilatation, implanting the device only in reference vessels of the same size, and postdilatation. It is also recommended small vessels and ostial lesions be avoided. In doing so, they have significantly reduced the incidence of scaffold thrombosis, cutting the 1-year rate from as high as 3.0% to less than 1.0%, he reported.

“You really have to take care at the time of implantation,” said Gori. “Once we’ve become conscious about it, the general trend in all of the registries is that rates of scaffold thrombosis are going down.” He said he believes the rate of scaffold thrombosis in BVS Expand can be reduced even further, as physicians today are more aware about the potential risks with the “less forgiving” stent.

Good News, Though Caveats Remain

In an editorial, Huay Cheem Tan, MD, and Rajiv Ananthakrishna, MD (National University Heart Center, Singapore), write that patients treated in the BVS Expand registry are reflective of clinical practice, noting that 38% had type B2/C lesions, 21% had bifurcations, and 42% had calcified lesions. Regarding the findings, the clinical outcomes observed in the Dutch registry “reassures us of the medium-term performance of [Absorb] BVS,” they write.

Despite the reassurances, the unique advantages of a fully bioresorbable stent and polymer—designed to reduce the risk of late events—are not expected to manifest until the device has fully dissolved after 36 months. At 18 months, Expand BVS registry data are insufficient to address the potential plausible advantages of the stent, according to the editorialists. Not only that, but previously reported cases of late scaffold malapposition and very-late scaffold thrombosis have raised a “small red flag regarding the long-term safety of this novel technology.”

Like Gori, Tan and Ananthakrishna focus attention on the procedural and technical aspects of implantation with Absorb. In the registry, for example, just 39% of patients underwent a preprocedural intravascular ultrasound and optimal coherence tomography, which are useful in patient evaluation and to optimize device implantation. “A quarter of the recruited participants had scaffold underexpansion based on quantitative coronary analysis, with a trend for an increased rate of major adverse cardiac events in this subset,” they write. “Scaffold underexpansion is a known important risk factor for scaffold thrombosis and restenosis. This can be addressed if intravascular imaging modality is more commonly adopted.”

Regarding scaffold thrombosis, the overall and definite rates observed are similar to those observed in other Absorb BVS studies, but “still higher compared to second-generation metallic DES,” according to Tan and Ananthakrishna. “With a universal adoption of optimal implantation techniques and enhanced scaffold design, it remains to be seen whether scaffold thrombosis rates will be further reduced.”

Gori is cautiously optimistic about the future of the technology, saying he believes bioresorbable devices such as Absorb BVS have the potential to become workhorse stents in clinical practice. That time is not now, however. He told TCTMD the Absorb stent in its current iteration is a safe and effective option for approximately 20% of patients.

“I would strongly encourage people not to experiment too much with the device,” he said, noting that the safety of stent, which today has thick struts that can limit deliverability and which can be difficult to place in the anatomy of certain patients, will improve with second- and third-generation devices. He emphasized avoiding use in higher-risk patients, where the potential for complications is higher. “It might be safe in certain hands, but it’s not something that should be advertised,” said Gori. 

Related Stories:

• Now You See It: FDA Approves Absorb Bioresorbable Scaffold
• FDA Panel Overwhelmingly Supports Absorb Bioresorbable Stent
• ABSORB III: Novel Bioresorbable Scaffold As Good as Standard-of-Care DES