In the ABSORB III three-year and ABSORB IV 30-day analyses, the bioresorbable vascular scaffold (BVS) was associated with significantly more target lesion failure (TLF) and other adverse events than the everolimus-eluting stent (EES), according to results presented Oct. 31 at TCT 2017 in Denver. Based on these latest findings, the U.S. Food and Drug Administration has also released an updated letter to health care providers on BVS use.

ABSORB III, also published in the Journal of the American College of Cardiology, evaluated clinical outcomes over three years in 1,322 patients implanted with the BVS and 686 patients implanted with an EES. The primary endpoint was TLF through three years.

A one-year analysis demonstrated the non-inferiority of the BVS compared to the EES. At three years, TLF had occurred in 13.4 percent of BVS patients and 10.4 percent of EES patients (p = 0.06). Target vessel failure (TVF) and the composite endpoint of all death, all myocardial infarction (MI), or all revascularization through three years occurred more frequently with BVS than EES. Target vessel MI (TVMI) through three years occurred in 8.6 percent of BVS patients vs. 5.9 percent of EES patients (p = 0.03), mostly driven by increased MI related to device thrombosis (p = 0.02). No stent thromboses occurred with EES after one year. There were no significant differences between the groups in all-cause or cardiac death. BVS vs. EES implantation was an independent predictor of TLF and device thrombosis through three years.

The ABSORB IV trial was conducted in an expanded patient population in which small vessels were avoided and aggressive pre-dilatation and routine high-pressured post-dilatation were encouraged. Patients were randomized to receive either BVS (n = 1,300) or EES (n = 1,300). The primary endpoints were TLF at 30 days (non-inferiority) and TLF between three and seven to 10 years (pooled with ABSORB III).

At 30 days, TLF occurred in 5.0 percent of BVS patients and 3.7 percent of EES patients (p = 0.11). TVF occurred in 5.1 percent of BVS patients and 3.7 percent of EES patients (p = 0.07). The composite of death, MI, and revascularization occurred in 5.2 percent of BVS patients and 4.1 percent of EES patients (p = 0.17). Device thrombosis occurred in 0.6 percent of BVS patients vs. 0.2 percent of EES patients (p = 0.06).

The results of ABSORB III showed that three-year rates of composite adverse events were increased with the BVS vs. EES, driven by greater scaffold thrombosis and TVMI. The authors suggest that "longer-term clinical follow-up is necessary to determine whether normalization of vascular structure and function after complete scaffold bioresorption will result in a favorable late net safety and efficacy profile of BVS compared to permanent metallic drug-eluting stent (DES)." Meanwhile, the ABSORB IV results are largely consistent with those from earlier ABSORB trials, including ABSORB II the exploratory results of which were also presented at TCT 2017, and found no statistically significant differences in clinical outcomes at four years.

ABSORB IV investigators "emphasize the need for advancements in device technology and standardized technique to further improve the early safety profile of BVS." In a broader analysis of all the ABSORB trials published in the Journal of the American College of Cardiology, Stone et al. note that "improved technique (in particular avoidance of small vessels) and optimizing scaffold expansion through effective lesion preparation and post-dilatation, along with generational device enhancements (thinner struts and greater capability for expansion without fracture) may improve the intermediate-term safety profile of BVS."

In the meantime, the FDA continues to recommend that health care providers: follow the instructions for target heart vessel selection (e.g., avoiding BVS use in small heart vessels) and optimal device implantation that are included in the BVS physician labeling; Advise patients experiencing any new cardiac symptoms such as irregular heartbeats, chest pain, or shortness of breath to seek clinical care; Advise BVS patients to follow the recommendations for dual antiplatelet therapy prescribed by their health care providers; and report any adverse events related to the BVS through MedWatch.

As for the future of BVS', Spencer B. King III, MD, MACC, and Bill D. Gogas, MD, PhD, write in a JACC Editorial that "the improved platforms that make scaffold implantation as user friendly as metal stent implantation…will be required to match the very high bar already established by metal DES." "For the time being, although the ABSORBing scaffold has vanished, we believe that improved disappearing technologies will eventually reappear; but whether they will be competitive with current and future coronary stents remains questionable."

Keywords: TCT17, Transcatheter Cardiovascular Therapeutics, Coronary Artery Disease, Absorbable Implants, Physical Phenomena, Drug-Eluting Stents

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