FDA Warning on Absorbable Stent, Researchers Blame User Error

There was discouraging news on bioresorbable stents today.

In a “Dear Doctor” letter released this morning, the US Food and Drug Administration (FDA) said it was investigating higher risks of stent-related thrombosis and other major cardiac events in patients who got the Absorb GT1 bioabsorbable vascular scaffold (BVS) stent than in patients who go the approved metallic XIENCE drug-eluting stent.

The Absorb GT1 is made by Abbott Vascular.

The FDA said two-year data from the ABSORB III trial showed an 11% rate of major adverse cardiac events compared with a 7.9% rate in patients who got the XIENCE device, also made by Abbott.

That news came this morning even as researchers were discussing findings from ABSORB III at the ACC Scientific Sessions.

In that report, Cleveland Clinic researchers agreed there were problems but said “results may not ultimately portray the potential for the stent’s future success.”

Speaking at a news conference this morning, Cleveland Clinic’s Stephen Ellis, MD, (photo) said he had been informed of the FDA warning letter. After getting a copy and reading it at the news conference, Ellis said the mishaps were likely related to faulty stent placement, lack of user experience, and by placement in vessels that were too small to meet the FDA criteria for use of the device. The stent was approved in July 2016.

The ABSORB III trial enrolled 2,008 patients at 193 centers. Patients were randomized to either BVS (1,322) or a drug-eluting metallic stent (686 patients). The study’s primary endpoint was target lesion failure, as measured by a composite of cardiac death, target lesion heart attack and ischemia-driven target lesion revascularization. That occurred in 10.9% of patients in the BVS arm compared to 7.8% of patients in the drug-eluting stent arm.

In issuing its warning this morning, the FDA advised physicians to avoid using the stent in small heart vessels and to review the procedures for placing the device.

At the news conference, Ellis said that when the stent is not placed properly it does not get implanted into the vessel wall and the wall does not heal over the device as it should while the stent dissolves. It takes three years to dissolve.

“The device can flop into the lumen and is thrombogenic,” he said. Still, only 4 patients of 1,400 experienced scaffold clots.

He added that “devices are different than drugs” in that user experience and user error are more crucial.

“Results are getting better,” he said.

Commenting on the study and the FDA warning, panelist Dipti Itchhaporia, at Hoag Hospital, California, cardiologist said “Enthusiasm for ABSORB has already come down; it’s bulky, more difficult to implant but it’s a first generation of this device and the company has a new version.”

The takeaway could be that patients who get these stents should be continued longer on dual antiplatelet therapy, she said.