FDA Panel to Weigh Value of Drug-Coated Stents
Safety concerns are raising doubts about the artery-opening devices
WEDNESDAY, Dec. 6, 2006 (HealthDay News) -- When a U.S. Food and Drug Administration advisory committee begins a two-day session Thursday to examine the safety of drug-coated stents, thousands of cardiologists and millions of patients will be paying close attention.
Coated stents have dominated cardiovascular surgery since their introduction several years ago. Some 2 million to 3 million people in the United States now carry one of these devices in an artery, according to the latest FDA estimates, with implantations topping 900,000 per year.
But a number of studies have now suggested that these coated stents, which can cost thousands of dollars each, have long-term dangers -- most specifically, the risk of thrombotic artery blockages that can cause heart attacks. So, cardiologists are trying to assess the risk vs. benefit equation for coated stents.
That means that this week's meeting "will be a very closely watched panel," said Dr. Deepak Bhatt, an interventional cardiologist at the Cleveland Clinic. "Cardiologists are looking for guidance and will be very receptive to whatever comes out of that meeting."
But the controversy is already affecting medical practice, Bhatt said. His team published a study that found a slight increase in thrombotic events -- about 0.5 percent -- in patients getting coated rather than bare-metal stents.
So, Bhatt has cut back on his use of coated stents, "probably from 90 percent to 80 percent of my patients." And, he said, other cardiologists are being "a little more cautious about the implants or are extending the duration of anti-clotting medications."
Anti-clotting medications such as Plavix (clopidogrel) and aspirin are important because doctors often prescribe them after stent implantation. And research published earlier this week linked the increased risk of thrombosis to discontinuation of one such drug, Plavix.
"This raises the question of whether these drug-eluting stents should be anticoagulated for a long period of time," noted Dr. John Kao, assistant professor of medicine at the University of Illinois at Chicago. "What that time period is, is at this moment unclear."
The American Heart Association released a cautious statement saying that "there is conflicting data regarding the magnitude and significance" of the increased risk of late thrombosis in patients getting coated stents.
What is clear is that "it is very important that patients do not discontinue their anti-platelet therapy within a year after stenting without consulting their treating cardiologist," the heart association statement said. The risk of discontinuing Plavix therapy is less clear, it said.
"Additional studies probably will be required to define the risk of late blood clots in patients with drug-eluting stents and the appropriate therapy to prevent them," the association statement said.
There are other angles to the drug-coated stent issue. Stenting and its follow-up treatment is now a very big business. Two brands of drug-coated stents are sold in the United States -- one, brand-named Taxus, is marketed by Boston Scientific Corp., while another, Cypher, is made by Cordis Corp., a subsidiary of Johnson & Johnson. And a number of physicians invited to participate in the FDA advisory committee have ties to one or another of these companies.
For example, one panel member is Dr. Robert A. Harrington, who heads a research unit at Duke University that gets funding from Boston Scientific and Johnson & Johnson. In all, six of the experts summoned by the FDA have such ties to heart device manufacturers.
However, Dr. Daniel Schultz, director of the FDA's Center for Devices and Radiological Health, defended the composition of the group during a news conference Tuesday.
"Whether or not waivers were granted or not granted, it was important that we had a panel of individuals who were able to give us objective, non-biased information," Schultz said. "Looking at the entire panel, if you look at that objectively, you will see that we have done a pretty good job of achieving that goal."
Another issue: the cost to patients of Plavix, which can total $120 or more a month. Current guidelines recommend that Plavix be taken (along with aspirin) for three months if a Boston Scientific coated stent is implanted and for six months with a Cordis stent. Because the drug can be so expensive, Kao said he sometimes makes his decisions on implanting a bare-metal or coated stent on the basis of a patient's income.
"When I evaluate someone who needs intervention who is on a fixed income and cannot afford to take Plavix for six to 12 months, I put in a bare-metal stent," Kao said.
For patients who can afford the drug, "my recommendation now is to take it for one year, indefinitely if they can afford it," he said.
But there are medical considerations in prescribing Plavix, Bhatt said. The medication can cause dangerous bleeding, he said, so he evaluates patients for bleeding risk before prescribing the drug.
Cardiologists in Europe now are "a little more cautious about extending the duration of anti-clotting medications," and the same is becoming true in the United States, Bhatt said.
The issue of possible clots is not the only consideration when weighing the need for drug-coated stents, said Dr. Joseph B. Muhlestein, a professor of medicine at the University of Utah. His group has followed patients receiving stents very carefully and has found "something we don't understand," he said.
As expected, the drug-coated stents did reduce the incidence of artery closure at the site where they were implanted, Muhlestein said. But the incidence of artery problems at other sites occurred "significantly more often than when we used bare-metal stents," he said. So, the overall incidence of artery problems ended up being the same, regardless of stent type, Muhlestein said.
It is possible that the problem occurred because coated stents were used on more high-risk patients, he said. But it's also possible that the coated stents interfered with the endothelium, the delicate tissue that lines the arteries -- something also reported in a Dutch study.
These doubts about the value of coated stents have caused Muhlestein to cut back on their use. "We used to use them in 90 percent of cases," he said. "Now, it's about 40 percent."
What does all of this mean for someone facing a stent implant? "At this point, in the absence of more information, the kind of stent should be the subject of discussion between patients and cardiologists," advised Dr. David F. Kong, an assistant professor of medicine at Duke University.
To learn more on stents, head to the American Heart Association.