FDA Panel Affirms Safety of New Artery Stents if Used Properly
Friday, December 8, 2006
Drug-releasing stents used widely to keep clogged heart arteries open may increase the risk of potentially dangerous blood clots, but there is no conclusive evidence that the devices boost the likelihood of having a heart attack or dying if used as recommended, an expert panel said yesterday.
The conclusion by a special Food and Drug Administration panel should be reassuring to hundreds of thousands of patients who have the tiny mesh struts, known as drug-eluting stents, which have become the most commonly used devices for treating partially blocked arteries.
"The message is: Drug-eluting stents are safe, and the safety concerns are far outweighed by the evidence of a clinical benefit," said William H. Maisel of the Beth Israel-Deaconess Medical Center in Boston.
Maisel, who chaired the 21-member panel, and others cautioned that the reassuring conclusion applied only to patients for whom the devices were originally approved. At least 60 percent of those getting them are sicker patients, and for them the risk-benefit calculus may be different. The panel will consider that issue today.
The discussion revealed deep disagreement and uncertainties among the FDA advisers. The panelists agreed there was insufficient evidence to conclude that the overall risk of heart attacks and death was greater among those getting the drug-eluting stents compared with those who received older bare-metal versions. But the panel was divided about whether the devices increased the risk of clots. Some panel members also remained concerned about the long-term safety of the devices, which have been implanted in 2 million to 3 million Americans.
"I have seen nothing to date that indicates that the problem goes away," said Steven E. Nissen, president of the American College of Cardiology. "It's a bit scary if the rate is constant. In the long run, it may not be such a good bargain."
The safety of the devices has been debated intensely because the number of people getting them has risen dramatically since they were introduced in 2003. Worldwide, an estimated 6 million people have drug-eluting stents, and about 800,000 Americans get them each year.
In response, the FDA convened an urgent two-day meeting to evaluate the devices.
Hundreds of people packed a large Gaithersburg meeting room for the highly anticipated session, including representatives from Johnson & Johnson and Boston Scientific Corp., which make the two brands of drug-eluting stents sold in the United States. The companies presented data they said indicated that any increased risk in getting blood clots was offset by the devices' ability to sharply reduce the need for surgical treatment, which carries its own risks.
The FDA is not bound to adopt the panel's recommendations but usually does.
More than 1 million heart patients a year in the United States undergo procedures to open blocked arteries with tiny balloons and then install stents -- hollow lattice tubes -- to keep the passageways open. Scar tissue often grows around the stents, however, narrowing the arteries again and requiring patients to undergo the procedure repeatedly, or to have bypass surgery.
The new generation of stents are coated with a polymer impregnated with drugs that filter out slowly, inhibiting scar tissue growth. Because the devices were shown to be highly effective, they were hailed as a major advance and quickly replaced the bare-metal versions for most patients, even though they were approved only for low-risk patients. Many of those receiving the devices "off-label" have multiple blockages, diabetes and other complications that may make them riskier candidates for getting the devices.
Scientists became concerned that the slower healing around the devices may prolong the risk of clots, which can also block arteries and cause heart attacks and death. Alarm intensified in recent months as studies looking at patients outside tightly controlled clinical trials indicated that a year or more after implantation, patients with drug-coated stents faced a small but meaningful increased risk of clots, compared with those given bare-metal models, and possibly were experiencing more heart attacks and sudden death.
FDA scientists, who opened the session by summarizing existing data, concluded that the devices do carry an increased risk of blood clots. But the agency's experts noted that the studies' design and size were not sufficient to reach any firm conclusions about whether that translates into more heart attacks and deaths.
Patients who get the stents are advised to take aspirin and an anti-clotting drug known as Plavix for at least three to six months to reduce the risk. Recent studies have indicated that they may need to take the drugs longer -- perhaps indefinitely. Plavix, however, is expensive and increases the risk of potentially serious bleeding problems.
The panelists urged the agency to update the devices' labels to make the benefits of taking anti-clotting drugs clearer.