FDA Probing Absorb Stent

The FDA is investigating the Absorb scaffold's elevated rates of major adverse cardiovascular events and scaffold thrombosis, the agency announced.

At the heart of the issue is the 11% rate of major adverse cardiac events with this device at 2 years compared with 7.9% for the Xience drug-eluting stent (P=0.03), as observed in the ABSORB III trial. Another major problem with the scaffold was its numerically higher rate of stent thrombosis (1.9% versus 0.8%).

“The FDA’s letter to healthcare providers emphasizes the importance of following instructions for use when implanting Absorb,” Abbott vascular said in an emailed statement. “When implanted in appropriately-sized vessel sizes and following current instructions for use, the results for Absorb are comparable to the leading metallic drug-eluting stent — with the added feature of leaving no metal behind once it dissolves.”

The company noted that the FDA communication was a healthcare provider update rather than a warning or safety letter.

"Whoa," was the response of E. Magnus Ohman, MBBS, of Duke Clinical Research Institute in Durham, N.C.

"This is somewhat surprising in one level because most of us had been enthusiastic about using bioabsorbable scaffolding to remove that permanent metallic stent in our vessels," he told MedPage Today at the American College of Cardiology meeting in Washington, D.C., where the ABSORB III data was due to be presented.

He likened it to the paradoxical situation with drug-eluting stents versus bare-metal stents in the 1990s. "Interventional cardiology is fascinating in that it takes two steps forward and then usually one back."

Deepak Bhatt, MD, MPH, of Brigham and Women's Hospital toll MedPage Today that early data from the ABSORB series of trials suggested a signal for increased risk of stent thrombosis, so he was not surprised. At this point, he added, it is difficult to make a case for use of the stent over second generation everolimus-eluting stents like Xience, which are cheaper and appear to be safer.

While the FDA conducts further analyses in tandem with Abbott Vascular to understand the cause of these events, operators are being told to stick to good implantation technique and continue avoiding small vessels. Adverse events should also be reported to MedWatch, according to the agency.

"In this particular case, it may have been that high-pressure delivery of the bioabsorbable stents, that was not traditionally done, in this trial may actually play out to be really important," Ohman added. "But I also think that it's up to the ABSORB investigators that the newer technology, the better use of imaging, and those really make a difference. Because we know this is occurring on the background of dual antiplatelet therapy, which is obviously why there is some concern."

The Absorb scaffold got FDA approval in July 2016.

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