In Cold Blood
An expert panel considers a chilling possibility: The most popular type of stent may be unduly risky
For 4 million Americans whose intimate wear includes a tiny, drug-coated cylinder of metal wire, lodged in a coronary artery to prop it open, these are anxious times. Could coated stents, which in just a few years have become the treatment of choice in people with heart blockages, be putting them at higher-than-expected risk of a killer clot? This week, a Food and Drug Administration panel will convene to consider the evidence, which began trickling out in the spring and galvanized a global meeting of heart specialists in September.
It was not news that the devices can promote clots–with either a drug–coated stent or an uncoated, "bare metal" stent, blood-thinning medication is necessary for a time. What took clinical researchers aback was the prospect of a continuing toll from coated stents, year after year, in lives and heart attacks. When Johnson & Johnson's coated Cypher stent was approved by the FDA in 2003, it was hailed as a potent weapon against restenosis, the tendency of a blocked coronary artery to close up again shortly after being reopened. Historically, vessels opened by an angioplasty balloon-jammed into the blockage and inflated to squash it against the artery walls-reblocked within a year or less as often as 40 percent of the time. That meant another procedure, or surgery.
Slow growth. Bare-metal stents, introduced in the 1990s as scaffolding to keep reopened vessels from closing, cut the restenosis rate to between 15 and 30 percent. And the Cypher squeezed it below 10 percent–in most trials, far below. A coating of rapamycin, a powerful medication leaked at a controlled rate into the artery wall, successfully discouraged tissue regrowth. Together with Boston Scientific's paclitaxel-coated Taxus stent, which arrived in 2004, coated stents quickly relegated bare metal to a token 10 percent or less of the market.
In hindsight, the revolution may have happened too fast. A loud alarm was sounded at the September heart meeting by cardiologist Edoardo Camenzind, a researcher at the University Hospital Geneva in Switzerland. He reported that in patients with Cypher stents in Europe and elsewhere who were tracked for three years, death and heart attack rates were far higher than in patients who got bare-metal stents–6.3 percent vs. 3.9 percent. The rates for Taxus patients also rose, if less dramatically. The cause, Camenzind concluded, was clotting: late thrombosis. A just-published study in the American Journal of Medicine seems to buttress that conclusion: Among 6,675 stented patients in a variety of trials worldwide, none with a bare-metal stent experienced clotting after the first year, while 0.5 percent of coated-stent patients did.
Camenzind's revelation spurred researchers and manufacturers to dive back into their data, and the FDA–which declined to comment for this article because of the pending meeting–decided to put everything back on the table this week. The panel might even reach a conclusion as soon as the meeting is adjourned.
A few in the medical community had seen this coming. Approval of medical devices often rests on data generated by a few hundred patients who may not represent the real world–they're relatively easy to treat. With coated stents, that was reflected in the FDA approval letter: They were deemed appropriate for patients with a single, compact blockage. It should be neither too long nor too short, and the artery neither too wide nor too narrow.
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