Heart Stents and FDA Blockage
Is it another medical breakthrough gone unexpectedly bad?
The drug-eluting heart stent is under increased scrutiny because of a complication that was not apparent when it was first approved by the Food and Drug Administration (FDA). FDA hastily convened an advisory panel last month to consider safety concerns about these stents, after some recent studies found a slight but unexpected risk of blood clots from them. The studies have sparked alarmist press reports and worry among many patients and doctors. Should FDA restrict their future use? Should patients with the stents actually have them removed?
When the stents were first approved by FDA in 2003, they represented a major advance in treating coronary heart disease, which affects more than 13 million Americans and leads to heart attacks in half of them. Coronary artery bypass graft surgery became available in the 1960s and greatly decreased the mortality rate from these myocardial infarctions. A safer, non-surgical treatment, balloon coronary angioplasty to reopen blocked arteries, was introduced in the 1980s, but 40% of these procedures were complicated by re-stenosis—that is, a reoccurrence of such blockages. The next innovation was the metal stent, which was introduced in 1994. This metal tube, inserted to hold the coronary artery open, further reduced the re-stenosis rate to 20%-30%.
But in some cases these bare metal stents themselves posed a risk of triggering restenosis by delaying healing of the artery. And so the drug-eluting stent was developed, covered by a polymer coating that slowly releases an anti-stenosis drug. These stents, introduced in the US in 2003, further reduced the re-stenosis rate by two-thirds and cut all major side effects by nearly half, compared to the bare-metal stent. These life-saving advantages led to quick acceptance, and today about 3 million patients in the US have these new stents.
But attention has now focused on a newly-recognized complication of the coated stent—the possibility of artery-blocking blood clots. Such potentially deadly clots were always a risk with metal stents; they occurred in less than one percent of cases, usually soon after the stent's insertion. The drug-eluting stents greatly reduce that risk, but some new studies indicate they may increase the blood clot risk months or years later. Whether that later risk offsets the earlier benefit of these stents is still open to debate; in the view of many cardiologists, the new stents are still a major improvement.
Some claim that FDA should never have approved these stents in the first place, and that the agency is too quick to approve new therapies. But this story is far from over. Many cardiologists, for example, intend to keep using the new stents, even though some may alter their selection of patients to further reduce the risks.
This debate raises important questions. All scientific advances come with risks. If we insist on knowing complete knowledge about those risks before we approve a new therapy, we may never get new therapies at all. So who should make the decision? Should we concentrate even more decision-making power in FDA, or should we leave it up to patients and their physicians?
FDA is a scientific bureaucracy with police powers. Patients and physicians are free to choose only those drugs and medical devices that it has approved. When FDA approves a therapy that later turns out to be unexpectedly risky, the agency is the subject of front-page headlines and congressional hearings. On the other hand, when FDA delays a badly needed new therapy, patients will suffer but hardly anyone will blame FDA. We'll just think that medical science can't help these patients.
Consider, for example, FDA's 10-year delay, in 1967-76, in approving beta-blockers to prevent death following heart attacks, because of the agency's fear that the drugs might be carcinogenic. During those years, the drugs saved lives in Europe and elsewhere, while an estimated 10,000 heart attack victims unnecessarily died in this country each year. When beta blockers were finally approved in the US, to wide acclaim, hardly anyone raised the lethal effects of FDA's slowness.
Even FDA's 2003 approval of drug-eluting stents was, in the view of some critics, an example of "deadly overcaution". The devices were approved for use in Europe in 2002, and the one-year delay before FDA's approval clearly injured many Americans. By some estimates, an estimated 50,000 Americans suffered unnecessary complications, including heart attacks and death, during that time.
We don't yet know the FDA's final response to its advisory panel recommendations. The panel concluded that there was not enough evidence to justify any changes to FDA's current recommendations. But given the agency's long history of overcaution, this episode may lead FDA to further prolong approval times by requiring even lengthier clinical trials for still newer types of drug eluting stents that promise to be even safer.
As a doctor, I think that would bad a mistake. As someone who might need a stent in the future, I think it would be a deadly mistake.