Devices & Diagnostics

Vanishing stent vs durable stent wars continue

Abbott Vascular's Absorb bioresorbable stent that disappears into the body over time seems to be coming up short compared with the company's durable drug-eluting stent, Xience.

corporate battle

The initial results are in and it doesn’t look that great for vanishing or bioresorbable cardiac stents that are designed to dissolve into a patients’ body over time compared with durable drug-eluting stents that leave an implant behind.

And if there aren’t superior outcomes, the rationale for forking over more money for bioresorbable polymer DES technology also … ahem vanishes.

At the annual Transcatheter Cardiovascular Therapies conference last week in Washington, D.C., Abbott presented three-year data on its Absorb bioresorbable polymer stent that is used to open clogged arteries and elute everolimus. The device is supposed to disappear from the body in two to three years. The device – Absorb GT1 BVS (bioresorbable vascular scaffold) won regulatory approval from the Food and Drug Administration in July. It won approval in Japan on Monday.

The Absorb II trial had two co-primary endpoints, according to Glenn Novarro, an analyst with RBC Capital Markets who attended the meeting and published a research note. They were Absorb’s superiority over Xience, Abbott’s very own durable drug-eluting stent and the gold standard in DES, in angiographic vasomotor reactivity and non-inferiority of angiographic late luminal loss.

Absorb failed to meet both those endpoints.

In layman’s terms, vasomotor reactivity (VMR) is defined as the percent change in blood flow velocity in response to changes in carbon dioxide. Late lumen loss is the difference in millimeters between the diameter of a stented segment following the placing of a stent, compared with the follow-up angiogram at six or nine months.

What’s worse, the device was also associated with a “two-fold increased risk of device-oriented clinical events, specifically an increased risk of target-vessel myocardial infarction (heart attack), as well as an increased risk of late scaffold thrombosis compared with Xience” according to TCTMD. Here, a thrombus or blood clot suddenly forms in a stented coronary artery impeding blood flow and is a life-threatening complication.

“It’s not what we were expecting,” said lead investigator Dr. Patrick Serruys, according to TCTMD. “Of course, we’re still in the first generation. I think, in general, physicians and patients would like to have something that disappears. Conceptually, if there was no setback or tradeoff, they would [choose] that. From what I’ve seen over the past few years, there is room for improvement.”

Meanwhile, better news regarding vanishing stents was not to found even in Absorb III data which met its safety endpoint. Here’s how Novarro described the data there.

The observed rates of cardiac death and target vessel myocardial infarction and scaffold/stent thrombosis were numerically higher in the Absorb stent group. The scaffold/stent thrombosis rate was more than 2-fold higher in the Absorb group than in the Xience group. There was a clear signal for increased cardiac safety events when Absorb was placed in small vessels. This signal was more pronounced in diabetics. Finally, there was no evidence of higher device or procedure success rates, or 1-year clinical outcomes, when post-dilatation was performed.

But Novarro noted that registry data painted Absorb in a better light suggesting that “following the prescribed procedure guidelines with Absorb does make a difference in the end result.” For instance, the Absorb Extend registry showed that Absorb’s clinical safety and effectiveness was comparable to those of Xience V stent and there was no statistical difference between Absorb and XIENCE V with regards to major adverse cardiac events, myocardial infarction, and late stent thrombosis.

Still, one cardiologist who looked at other data of bioresorbable polymer stents compared with drug-eluting stents that did not involve Absorb seems to have arrived at three pretty strong conclusions, per Novarro’s note: Dr. Sigmund Silber of Heart Center at the Isar, Germany, believes that (1) so far, no evidence-based clinical data exist that show superiority of biodegradable polymer-based over durable polymer-based DES; (2) modern DES with durable polymers are the “gold standard” and hard to beat; (3) Avoiding biodegradable polymer-based DES does not put the patients at risk and saves health care costs.

Needless to sat Dr. Silber doesn’t use vanishing stents in his practice.

Photo: THEPALMER, Getty Images

 

 

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