Stents under new scrutiny
For William Maisel, the big question about the springlike devices known as drug-coated stents is why safety questions took so long to surface — and why answers are still in short supply.
The stents, which were approved four years ago, have been implanted in an estimated 6 million people worldwide to keep arteries open after angioplasty. Last March, Swedish researchers linked their use to rare but dangerous blood clots. On Monday, The New England Journal of Medicine released several studies of the stents' safety and an editorial noting that the concerns "are far from resolved."
Maisel, chairman of a government advisory committee that met in December to address stent safety, wants to know why. "Several years have passed, millions of devices have been implanted, and here we sit in 2007 without all the answers we could have had," says Maisel, of Beth Israel Deaconess Medical Center and author of a commentary in the journal.
The stents' drug coating keeps scar tissue from clogging arteries, a common complication with stents made from bare metal. But the drugs used in the stents appear to promote clots. Doctors now say patients shouldn't be given drug-coated stents unless they can take anti-clotting medications for a year or longer.
The studies in the journal, presented at the Food and Drug Administration's December meeting, carry seemingly conflicting results. A Swedish registry of about 20,000 patients who did not participate in company-sponsored trials revealed five to 10 more deaths or heart attacks for every 1,000 patients a year who wear drug-coated stents compared with those who wear bare metal ones.
In contrast, a study of more than 5,000 patients in nine clinical trials found slightly higher rates of blood clots but no differences in deaths or heart attacks.
Researchers link the differences to the circumstances in which the stents were used. Drug-coated stents were approved for use in relatively simple blockages. But 60% of the patients who get them in practice are sicker, with more complex blockages.
The FDA's Ashley Boam and Andrew Farb say they worried that the devices would be widely used "off label," and they required manufacturers to follow all patients for five years. But the FDA was on alert for major problems soon after the stents were implanted, but no one expected to see "late-term events," Boam says.
Maisel says that regulators could have anticipated more events when the devices were implanted in millions of patients and that the agency and manufacturers could have sounded the alarm sooner: "It would have been nice to see the data earlier."
“Not what we say about our blessings, but how we use them, is the true measure of our thanksgiving.”