Study: Increased rate of major cardiac events with Abbott's Absorb bioresorbable vascular scaffold

In a letter to healthcare providers, the FDA warned there is an increased rate of major cardiac events in patients receiving Abbott's Absorb GT1 bioresorbable vascular scaffold (BVS), when compared to patients treated with the company's metallic Xience drug-eluting stent.

The FDA approved the Absorb GT1 vascular scaffold system last July, making it the first fully dissolving heart stent available to treat coronary artery disease in the US. The authorisation was based on one-year data from the ABSORB III study, which suggested that clinical results in patients treated with Absorb GT1 BVS were comparable to those treated with the Xience stent. As a condition of approval, the FDA required Abbott to follow patients in the trial for five years.

According to the FDA, an initial review of two-year data from the ABSORB III trial showed an 11-percent rate of major adverse cardiac events, such as cardiac death, myocardial infarction or the need for an additional procedure to re-open the treated heart vessel, in patients treated with the BVS, versus 7.9 percent in patients treated with the Xience drug-eluting stent. The regulator added that the rate of developing thromboses was 1.9 percent and 0.8 percent for the two devices, respectively. "These observed higher adverse cardiac event rates in BVS patients were more likely when the device was placed in small heart vessels," the FDA added.

The agency further noted that the two-year results are consistent with the trends observed in the recently published three-year results from the ABSORB II study and the recently presented two-year results from the ABSORB Japan study, which were conducted outside of the US. Among BVS-treated patients who developed device thromboses after one year in the ABSORB II, ABSORB III and ABSORB Japan studies, most had discontinued dual antiplatelet therapy, which is required with coronary stenting. The FDA added that the use of the recommended BVS implantation methods per the BVS physician labelling has been incorporated in the ongoing ABSORB IV study.

Stephen Ellis, who presented the ABSORB III trial data at the American College of Cardiology (ACC) scientific meeting, said all of the benefit of using the larger, more-difficult-to- place stent, "if there is going to be a benefit, will come after it has been fully absorbed." He added that "we await long-term outcomes. If this device doesn't produce better long-term outcomes, there's no point in using it."

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