FDA sees rare but serious issue with stents

Health regulators are investigating a rare but potentially serious problem with a newer class of heart stents that causes the tiny tubular devices made of wire mesh to shrink, or lengthen, after implantation.

The problem appears to occur most frequently in the Promus and Ion devices made by Boston Scientific Corp, the Food and Drug Administration said. Promus Element is sold outside the U.S. The company submitted a pre-market application with the FDA earlier this year.

The agency said it still views the Ion stent, which it approved for use in the spring, as safe when used for its authorized indications.

"FDA is actively working with (drug-eluting stent) manufacturers, including Boston Scientific, to better understand longitudinal stent deformation with respect to its causes, predisposing underlying anatomic conditions, operator techniques that can reduce the likelihood of its occurrence, and treatment strategies should it occur," the agency said in an emailed response to a Reuters inquiry.

Boston Scientific, the biggest manufacturer of stents with more than a third of the $4 billion global market, declined to comment on discussions with the FDA. Boston Scientific had a 36 percent share of the global market and a 49 percent share of the U.S. market at the end of the third quarter.

The company's business has struggled on several fronts in recent years, including a series of stent recalls that date to 2004 and a heavy debt load from its ill-fated acquisition of stent and pacemaker manufacturer Guidant Corp in 2006.

Concerns about stent deformation were raised in two smaller cardiology journals published in the U.S. and Europe, and the issue was the subject of a discussion at the Transcatheter Cardiovascular Therapeutics meeting in San Francisco earlier this month.

Drug-eluting stents prop open diseased arteries and deliver medicine to keep the vessel from reclogging. In the case of longitudinal deformation, the stents become deformed inside the vessel, creating a clotting risk that could lead to a heart attack.

Some factors that appear to predispose a patient to the problem include calcification of coronary arteries, implantation in a twisted blood vessel and improper positioning of the stent, the FDA said.

The FDA said that only one instance of longitudinal stent deformation was reported from trials of more than 4,600 patients treated with a Promus stent. But it said it was also aware of recently published case reports on the problem and that an unspecified number of significant adverse events had been reported to the agency.

"At this time, additional data collection and analyses are ongoing, but the information available to date indicates that the Ion Paclitaxel-Eluting Platinum Chromium Stent remains safe and effective when used for its approved indications," the agency said.