The FDA says it is working with drug-eluting stent makers to better understand what makes the devices shrink or become deformed on rare occasions. A drug-eluting stent is a scaffold placed into narrowed, diseased peripheral or coronary arteries; it releases a medication to block cell proliferation, which helps prevent eventual reclogging of the blood vessel. The DES (drug-eluting stent) is placed during an angioplasty procedure.
The FDA (Food and Drug Administration) says it is working closely with Boston Scientific Corp. the makers of several devices, including the Ion and Promus. The Ion stent was approved by the FDA this year, while earlier in 2011 Boston submitted the Promus Element for approval.
The FDA said to Reuters news agency:
"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."
PROMUS® Everolimus-Eluting Coronary Stent System (Photo: Boston Scientific)
Boston Scientific is said to have over one third of the global market for DES; a market worth over $4 billion annually. It has nearly one half of the US market.
Earlier this month, stent deformation was discussed at the Transcatheter Cardiovascular Therapeutics meeting, San Francisco. There are some factors in patients which increase the risk of problems when receiving a stent, including improper positioning of the device, implanting it in a twisted blood vessel, and calcification of coronary arteries.
Human trials involving 4,600 participants who received a Promus stent reported only one case of longitudinal stent deformation, according to the FDA. However, the Agency added that a number of adverse events had been reported to it - the FDA did not specify how many.
The FDA wrote:
"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."
Some studies have indicated that some patients might be better off if they do exercise and take medications than have a DES implanted.
Heart stents are fragile devices. They are made of extremely thin metal, about 3/1000 of an inch thick and cannot withstand more than a certain amount of pressure. Even during implantation, the balloon that is used during an angioplasty procedure can catch on the device and deform it. Pushing on the stent can also make it lose its proper form.
Because so many thousands of people receive these types of stents in the USA each year, even a small risk of stent deformation can mean a sizeable number of people.
Written by Christian Nordqvist