FDA Explores Safety of Heart StentsDec 7, 2006 | Washington Post
New drug-releasing stents used widely to keep clogged heart arteries open appear to increase the risk for potentially life-threatening blood clots more than older bare-metal versions, government investigators told an expert panel assessing the safety of the devices today.
But the blood clot risk from the tiny metal mesh struts, known as drug-eluting stents, appears relatively low and it remains unclear whether it translates into an excess risk for heart attacks or deaths, according to the Food and Drug Administration analysts.
Nevertheless, because some studies have suggested the increased risk of blood clots, known as thrombosis, may be causing thousands of excess heart attacks and deaths each year, it is urgent that experts determine whether their use should be restricted and patients who already have them should be treated longer with anti-clotting drugs, the agency officials said.
"Since stent thrombosis is associated with high rates of death and [heart attacks], continued efforts to clarify the mechanisms of stent thrombosis and interventions to reduce the risk of its occurrence will have public health benefits," the FDA's Andrew Farb said.
The presentations opened a two-day meeting of a special 21-member panel the FDA urgently convened to evaluate the stents, which have quickly become the most commonly used devices for treating clogged arteries. The panel will address a long list of questions, including whether the risks of the devices outweigh their benefits. The FDA is not bound to adopt the panel's recommendations, but the agency usually does.
Hundreds of people packed a large meeting room in Gaithersburg, Md., just outside Washington, for the highly anticipated meeting, including representatives from Johnson & Johnson and Boston Scientific Corp., which make the two drug-eluting stents sold in the United States. Other medical device makers, heart specialists, reporters and patient advocates also attended the meeting.
The safety of the devices has garnered unusually intense attention because the number of people getting drug-coated stents has risen dramatically since they were introduced in 2003. Worldwide, an estimated 6 million people have them, including as many as 3 million in the United States. About 800,000 Americans are getting the stents each year. Worldwide sales are estimated at close to $6 billion.
More than 1 million heart patients each year undergo procedures to open blocked arteries with tiny balloons and then to install stents--hollow lattice tubes--to keep the passageways open. But scar tissue often grows around the stents, 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 the growth of scar tissue. Because the devices were shown to be highly effective they were hailed as a major advance, and most patients now get them.
But scientists began to become concerned that the slowed healing around the devices may prolong the risk of blood clots, which can also block arteries, causing heart attacks and death. Alarm intensified in recent months as studies began reporting that a year or more after implantation, patients with the drug-coated stents face a small but meaningful increased risk of clots, compared with those given bare-metal models, and possibly were experiencing a greater rates of heart attacks and deaths. The excess risk appears to be small, but could translate into thousands of heart attacks and deaths because of the large number of patients receiving the devices.
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. But recent new studies have also indicated that may not be long enough and they may need to continue taking the drugs, perhaps indefinitely. Plavix, however, is expensive and increases the risk of potentially serious bleeding problems.
The FDA summarized the existing data, concluding that the evidence indicates the devices do carry an increased risk for 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 was translating into increased heart attacks and deaths. It also remained unclear whether extending Plavix use would be effective, the experts said.
The panel members began quizzing the FDA scientists about the findings, including whether the methods for identifying clots and assessing the risk were reliable.
"We think there is a small but significant increased risk in late-stent thrombosis," Farb said.
Boston Scientific and Johnson & Johnson, which have defended the safety of the devices, planned to present their analyses later in the day.