After reviewing data from a clinical trial, the FDA issued a letter to healthcare providers informing them that patients who received the Absorb bioresorbable vascular scaffold had an increased rate of major adverse cardiac events compared with patients treated with the Xience drug-eluting stent.

The FDA issued the safety alert on March 18.

In July 2016, the FDA approved the Absorb (Abbott Vascular) to treat patients with coronary artery disease. The approval was based on one-year results of the ABSORB III trial, which found that the Absorb GT1 was noninferior to Abbott’s FDA-approved Xience everolimus-eluting cobalt-chromium stent with regards to the primary endpoint of target lesion failure. The researchers defined target lesion failure as cardiac death, target-vessel MI or ischemia-drive target lesion revascularization.

The FDA based its warning on the initial two-year results from the ABSORB III trial. At two years, 11 percent of patients in the Absorb group and 7.9 percent of patients in the Xience had major adverse cardiac events, which the researchers defined as cardiac death, MI or the need for an additional procedure to re-open the treated heart vessel. The two-year rates of device thrombosis were 1.9 percent in the Absorb GT1 group and 0.8 percent in the Xience group.

“These observed higher adverse cardiac event rates in [Absorb] patients were more likely when the device was placed in small heart vessels,” the FDA wrote in its release.

The FDA also mentioned that healthcare providers have had improved clinical performance and a lower rate of complications when they follow the recommended Absorb implantation methods. The labeling recommends that healthcare providers choose appropriately-sized heart arteries and apply proper methods when implanting the Absorb.

The two-year results of ABSORB III were presented in a late-breaking clinical trial session at the American College of Cardiology scientific session in Washington, D.C. Abbott said in a news release that it emphasizes implant techniques during its Absorb training program. The company added that it requires physicians to undergo comprehensive training before they can implant the scaffold.

“When implanted in appropriate vessel sizes and following current instructions for use, the results for Absorb are comparable to XIENCE, the gold standard drug-eluting stent, with the added feature of leaving no metal behind once it dissolves,” Charles Simonton, MD, chief medical officer and divisional vice president of medical affairs for Abbott’s vascular business, said in a news release. “We look forward to data early next year from the ABSORB IV trial, which best represents current implantation technique.”

The FDA said it was working with Abbott to conduct further analyses to determine the causes of the higher cardiac event and device thrombosis rates in the Absorb group. The FDA added that it would continue to monitor the device in ongoing studies and reports submitted to the agency.

When the FDA approved the Absorb, the agency required Abbott to follow patients in the ASBORB III study for five years. The Absorb stent, which is made of a naturally dissolving material, typically disappears within three years of implantation, according to Abbott.