Boston Scientific Corp. (NYSE:BSX) must include the potential for stent "shrinkage" in the labeling for its newly cleared Promus Element drug-eluting stent.
The decision comes as concerns mount that certain thinner, more flexible next-generation stents may be prone to crumpling after deployment, creating clots in blood vessels that may lead to heart attack.
The decision may be related to a slew of recent studies looking at the potential for various stent models to deform under pressure. In a recent bench-test of seven different stents, including Medtronic’s Integrity and Cordis Corp.’s Cypher, a Boston Scientific stent, the Omega, warped under significantly less force than other models.
Boston Scientific’s Promus Element stent, which landed FDA clearance earlier this month, was the third-weakest tested among seven stents.
An Irish study published late in October was among the first to suggest that thinner stents may have lower longitudinal strength, potentially leading to stent thrombosis and a "catastrophic late complication" and leaving the target lesion unprotected, according to scientists at the Belfast Health & Social Care trust.
In mid-November a second study added further evidence that the thinner wire used to make next-gen stents might not be able to handle the pressure of percutaneous coronary interventions. Dr. Cindy Grines, editor of the Journal of Interventional Cardiology, detailed a case involving "marked shortening, deformation and accordion of BSX’s Ion coronary stent," something she hasn’t seen before in 25 years of practicing cardiology.
Citing data from a bench test conducted by Abbott (NYSE:ABT) "showing that the Element family of stents (including the Omega and Ion) may shorten up to 46 percent under the force that an interventional cardiologist may exert to advance a post-dilation balloon or intravascular ultrasound device, Grines called the results "very disturbing."
The FDA launched a probe into the reports soon after. Although there’s been only one reported incident of deformation involving a Promus stent from among more than 4,600 implantations in clinical trials, according to the federal watchdog agency, "an unspecified number of significant adverse events had been reported."
Stent shrinkage is relatively rare compared to other problems associated with clearing blocked vessels, BSX interim CEO Hank Kucheman told investors during the company’s third-quarter conference call.
"Stents have a lot of different properties, which vary from one to another," noted New York Presbyterian Hospital and Colombia University Medical Center director of cardiovascular research Dr. Gregg Stone during a conference call discussing the Belfast report. "Some stents will be more prone to this complication than others. The question is to understand how frequent it is, when does it occur, how to prevent it and how to manage it."
If determined to be a flaw, the news could affect the $4 billion stent market. That would leave Boston Scientific, which gets 20 percent of its revenues from drug-eluting stents, especially vulnerable.
Shares of BSX stock were down 1% to $5.07 by about 11:40 a.m. today.