WASHINGTON, D.C.—Fewer patients with coronary artery disease who were treated with a bioresorbable scaffold experienced new or worsening angina after treatment than similar patients implanted with metal stents in the ABSORB II trial. The one-year results were presented Sept. 14 at the Transcatheter Cardiovascular Therapeutics scientific session.
“Following the CE mark approval there was widespread dissemination of the bioabsorbable scaffold and that was without a randomized comparison with its metallic counterpart,” Patrick W. Serruys, MD, PhD, director of the Clinical Research Program at the Catheterization Laboratory at the ThoraxCenter at Erasmus University in Rotterdam, the Netherlands, explained at a press conference. The device is not approved in the U.S.
ABSORB II is a single-blind, multicenter randomized trial that was designed to evaluate the efficacy of an everolimus-eluting bioresorbable scaffold (Absorb, Abbott Vascular) compared with an everolimus-eluting metallic stent (Xience, Abbott Vascular). The presentation was the first glimpse at the data; the one-year follow-up findings were published simultaneously in The Lancet.
The study included 501 MI patients with one or two de novo lesions who were enrolled between 2011 and 2013, with 335 in the bioresorbable scaffold group and 166 in the stent group. The co-primary endpoints were vasomotion measured as change in mean lumen diameter between pre- and post-nitrate administration at three years and the difference between minimum lumen diameter post-nitrate administration after the index procedure and at three years.
The study included a device-oriented clinical endpoint, which was a composite of cardiac death, target vessel MI, or clinically indicated target lesion revascularization and a patient-oriented clinical endpoint, which was a composite of all death, any MI and all revascularizations.
At one year, the acute lumen gain was 1.15 mm in the scaffold group vs. 1.46 mm in the stent group based on quantitative coronary angiography and 2.9 mm2 vs. 3.6 mm2 based on quantitative intravascular ultrasound. The rate of new or worsening angina was 22 percent in the scaffold group vs. 30 percent in the stent group.
Exercise performance and angina stages assessed with the Seattle Angina Questionnaire were similar for the two treatments. “However, there was a difference in nitrate used observed at six months in favor of Absorb,” he said.
The composite device-oriented endpoint occurred in 5 percent of the scaffold group vs. 3 percent of the stent group and the composite patient-oriented endpoint totaled 7 percent vs. 9 percent, respectively.
“The good news is that in terms of events we are doing well,” Serruys said. “One point of concern is that when we started this trial the investigators were somewhat afraid of the fragility of the polymer so they were restraining themselves to use the whole pressure [and] volume of the balloon.”
That has been corrected, he said. He added that the angina findings need to be explored in further studies.
Discussant David G. Rizik, MD, director of the Heart and Vascular Division at Scottsdale Healthcare in Arizona, remarked that retrospective studies raised safety concerns with the bioresorbable scaffold, which ABSORB II may allay. “The device appears to be safe,” Rizik said, in this cohort studied.
He called the angina findings compelling and noted that a reduction in angina could provide cost savings for insurers.
The bioresorbable scaffold is designed to cover the vessel wall and slowly dissolve over time to be replaced by normal tissue. “The benefit will appear after two to five years, when we get rid of this cage,” Serruys predicted.
The study was funded by Abbott Vascular.