New Artery Stents Raise Safety Concerns
Wednesday, December 6, 2006
A flurry of recent research has raised alarm about the safety of a new generation of stents that have quickly become the most commonly used devices for treating clogged arteries, creating widespread concern about how to care for millions of heart-disease patients.
The stents, tiny drug-secreting mesh tubes used to prop coronary arteries open, appear to carry a small but significantly increased risk of causing blood clots, compared with older "bare metal" versions. That may boost the patients' chances of suffering a heart attack or dying, according to the studies, including one released yesterday.
The accumulating evidence prompted the Food and Drug Administration to convene an urgent two-day meeting of a panel of outside experts tomorrow to assess the devices, known as drug-eluting stents, including whether their risks outweigh their benefits.
"This is a public health issue of great importance," the FDA's Daniel Schultz said yesterday. "Our goal is to provide the American public with a coherent, understandable explanation of the risks and benefits associated with these products."
The situation, which has triggered an intense, sometimes bitter debate among cardiologists, illustrates the potential dangers of assuming that new technologies are necessarily superior and of adopting them widely before long-term studies are done, experts said.
"Everybody wants to be perceived as doing the most modern thing for their patients and fear being labeled someone who is old-fashioned and not using the latest and greatest thing," said Spencer King of the American College of Cardiology.
The issue also has major financial implications, with worldwide sales of drug-eluting stents now estimated at about $6 billion annually. Boston Scientific Corp. and Johnson & Johnson, which make the two drug-eluting stents sold in the United States, defend the safety of the devices.
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, which means that even a small increased risk could result in thousands of heart attacks and deaths.
"The potential risk appears to be relatively small," said Sanjay Kaul of the David Geffen School of Medicine at UCLA. "But the consequences of that risk can be catastrophic."
Many experts stressed that the devices are highly effective, enabling patients to avoid repeated artery-opening procedures and surgery, which can also be risky.
"Despite the risks, these devices do have clear advantages," said William O'Neill of the University of Miami. "We don't want to lose sight of that."
O'Neill and other specialists acknowledge that the concerns have already prompted many cardiologists to be more cautious about implanting the devices. Doctors are also trying to calm the fears of patients who have the new versions while struggling with a key question: How long should patients keep taking anti-clotting drugs, which are expensive and carry their own risks?
"This is raising concerns on many levels," King said. "One level is 'What do you do with a patient who already has one of these devices?' Another level is 'What do you do with a patient who needs one?' "
More than 1 million heart patients each year undergo procedures to open blocked arteries with tiny balloons and then to install stents 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.
That prompted the development of a new generation of stents 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, most patients now get them. The concern has been that the slowed healing around the devices may prolong the risk of blood clots, which can also block arteries, causing heart attacks and death.
In recent months, several studies have indicated 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. The excess risk is probably one per year in every 200 to 500 patients. Some studies also suggest that patients with the newer devices are more likely to have a heart attack or die.
"The risk to any individual patient is low, but if you are the one who suffers one of these events it obviously can be quite serious," said Deepak L. Bhatt of the Cleveland Clinic Foundation, who last week published an analysis of 14 studies that showed that drug-eluting stents are four to five times as likely to cause clots.
The FDA released its own assessment yesterday, concluding that the stents appear to carry a "small but significant" increased risk of clots. But the agency added that it remains unclear whether that translates into an increased risk of heart attacks and death.
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 two new studies indicate that is not long enough, including one reported yesterday by the Journal of the American Medical Association. The study was released early so the FDA advisers could include the findings in their deliberations.
The study, which involved more than 4,600 patients, found that those who stopped taking Plavix after six or 12 months were more than twice as likely to die or have a heart attack as those who stayed on the drug.
"The bottom line of our paper is that if you have a drug-eluting stent, for now you're well advised to continue taking Plavix, perhaps indefinitely," said Robert M. Califf of Duke University.
Plavix, however, is expensive -- about $4 per day -- and increases the risk of potentially serious bleeding problems.
As a result of the Plavix he was taking for two drug-eluting stents, Larry Fontana, 56, of Manhattan experienced excessive bleeding during an unrelated surgery.
"It's scary -- very scary," said Fontana, who opted for a bare-metal stent when he needed another one two weeks ago. "The drug-eluting stent was touted as being really remarkable, and I considered myself very lucky. Now it appears they have major problems."
Although experts said that they hope the FDA meeting will clarify some of the questions, many said that doctors and patients will probably have to make a more complicated, individualized weighing of the devices' benefits against the possible risks and costs.
"I think everyone is going to have to be much more aware of the potential dark side," said David L. Brown, a cardiologist at Stony Brook University in New York.