Registry data shows high risk of blood clot among users of Abbott's bioresorbable stent

Abbott's Absorb Bioresorbable Vascular Scaffold--Courtesy of Abbott

Data from a European postmarket registry show that Abbott's ($ABT) Absorb BVS bioresorbable stent performs at a level similar to today's conventional drug-eluting stents on several measures, but not stent thrombosis. The risk of the stent being blocked by a blood clot was 3.4% after one year, a level of performance similar to prior generation drug-eluting stents, according to a recent EuroIntervention study.

On other measures the device performed well. The rate of target lesion failure was 4.4% after 6 months, and 1% of patients suffered cardiac death within that time period, statistics the study authors described as acceptable. Also a positive was the technical success rate of 99.7%.

Unlike conventional drug-eluting stents which stay in the body permanently, bioresorbables such as Absorb are designed to degrade within the first year of deployment, resulting in reduced complications down the road and a continued increase in the size of the artery in the months following surgery. BVS is one of only two CE marked bioresorbable stents in Europe, where it has a market share of 5% to 10% of the overall stent market, according to market research firm GlobalData. Abbott says it will submit the product for FDA approval in 2015.

The study was conducted using data from 1,189 BVS patients gathered between November 2011 and January 2014 at 10 European centers via a data registry. Many of the patients would not be eligible for the ongoing Absorb II and Absorb III clinical trials because of the studies' strict entry criteria.

In spite of positive data supporting the BVS using other metrics, the worrying rate of stent thrombosis is the main takeaway from the study; the problem resulted in the deaths of three patients. It should be noted that the 3.4% rate is based on an annualization. The rate was 2.1% at the 6-month follow-up.

The study concludes that data "suggest that 'real-world' outcomes among 1,189 patients with relatively unselected clinical characteristics and lesions are acceptable and comparable to those reported in the literature for second-generation DES (drug eluting stent), with one-digit rates of target lesion and vessel failure at 6 months and low incidences of cardiac death and reinfarction. On the other hand, the scaffold thrombosis rate resembles that of first-generation DES, suggesting a negative impact of high strut thickness on this event."

Boston Scientific ($BSX) officials pounced on the stent thrombosis data during the company's July 24 earnings call. "Frankly, the 3.4% one year stent thrombosis rate is just not acceptable," said Boston Scientific Global Chief Medical Officer Keith Dawkins. "To put that in perspective, the Synergy (conventional drug-eluting) stent thrombosis rate of three years is zero percent, admittedly in a more simple patient population."

Abbott said in a statement emailed to FierceMedicalDevices that "this particular study was a retrospective, uncontrolled, site-reported study without independent adjudication of any events and lacked complete follow-up of all patients at even a short interval of 6 months." The company pointed to data presented at the 2013 Transcatheter Cardiovascular Therapeutics (TCT) conference showing that the device had the same rate of stent thrombosis as Abbott's conventional Xience drug-eluting stent.

More data on this topic are expected soon, Abbott said: "We look forward to additional compelling data coming soon from the Absorb II prospective, randomized trial in Europe, which will be presented at this year's TCT in September. Additionally, the Absorb III prospective, randomized trial in the U.S. will more accurately compare Absorb to a best-in-class DES. We fully expect that in prospective, controlled studies with full one-year follow-up data, Absorb will show very similar clinical outcomes to the latest generation DES."

- get the study abstract 
- read tctmd's take

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