THURSDAY, Dec. 4, 2003 (HealthDayNews) -- The risk of blood clots associated with a new drug-eluting stent appears to be no greater than for conventional bare metal stents, claimed those at a press conference Thursday organized by the stent's manufacturer.
What's more, any problems that are occurring seem to have more to do how the stent is inserted, not with the product itself, speakers at the conference said.
"In our experience, the product is safe and it's safe early on," said Dr. David Holmes, an interventional cardiologist with the Mayo Clinic in Rochester, Minn.
The U.S. Food and Drug Administration (FDA) approved the CYPHER Sirolimus-eluting Coronary Stent, made by Cordis Corp., in April. The drug sirolimus, which reduces inflammation associated with insertion of a stent, is marketed as Rapamune by Wyeth Laboratories.
Conventional bare metal stents have been used routinely since the 1990s to prop open clogged arteries that have been cleared by the technique called angioplasty. Stents can provoke inflammation and scarring, however, which can cause the artery to close up again.
Both bare metal and drug-eluting stents can cause clotting, especially in the first 30 days after the implant.
"When stent thrombosis occurs, you can have a mortality of even 50 percent, so this is something that is dreaded," said Dr. Eric Topol, chairman of cardiovascular medicine at the Cleveland Clinic and one of the lead investigators in clinical trials that led to the new stent's approval.
Since the stent was approved, the FDA has received a number of reports of clotting, including some involving deaths. The question is and has been: Is this any different than clotting that would have occurred with conventional stents?
The answer appears to be no, speakers at the news conference said.
The total rate of subacute thrombosis (SAT) for the Cypher stent is 0.76 percent, versus 0.45 percent for the bare metal stent, said Dr. Dennis Donohoe, vice president of clinical and regulatory affairs at Cordis. "This is not a significant difference," he adds.
"Real world" institutions -- hospitals -- that have been performing stenting have also not found any appreciable differences, with clotting rates of about 0.59 percent for the Cypher stent and 0.44 percent for bare metal stents, Donohoe said.
The number of reported problems with the Cypher stent peaked in July. At that time, both the FDA and Cordis released safety notices. Since then, the clotting rate has been creeping back down.
Three sets of instructions should help reduce the clotting rate, Donohoe said. Those are: proper use of stents, proper use of anticoagulant therapy, and proper patient selection. Not everyone is a candidate for a stent, he noted.
The risk of thrombosis (clotting) was increased by the use of longer stents and smaller diameter stents. Not all sizes were available before July, Donohoe said, which could have contributed to those early higher rates.
Also, blood vessel size needs to be accurately assessed because stents are not available for vessels that are less than 2.25 millimeters or more than 4 millimeters in diameter, said Dr. Jeffrey Popma, director of interventional cardiology at Brigham & Women's Hospital in Boston.
Although guidelines exist on how to use anticoagulation therapy in stent procedures, said Popma, "there still exists a tremendous heterogeneity about how anticoagulation is handled."
Added Topol: "These types of applications should be done with considerable caution."
And although a drug-eluting stent appears so far to be as safe as bare-metal stents, clotting remains a danger. "With more than 800,000 people undergoing coronary stenting, this is something we can't lose any consciousness or attentiveness to," Topol said.
More information
The American Heart Association has information on angioplasty and on conventional stents. Cordis has information on the Cypher stent.
