But 145,000 procedures were performed in nonemergency cases. In that group, just half of the angioplasties were classified as appropriate, 38 percent were rated as uncertain and 12 percent were found to have no benefit, Chan says. That's about 15,000 inappropriate procedures per year, he says, or about $300 million in needless medical spending.
A second study, published in the Archives of Internal Medicine, reviewed the insertion of stents more than 24 hours after a heart attack, a practice deemed "useless" in a major federal study in 2006.
Judith Hochman, M.D., a cardiologist at New York University, found that in the years after practice guidelines were revised to discourage placing stents in patients more than 24 hours after they had a heart attack, doctors nevertheless continued to perform the procedure at the same rate as before.
Hochman, who also led the 2006 study, says most people picture the circulatory system like household plumbing — if there's a clog somewhere in the line, it makes sense to open it. But it isn't that simple.
In patients with stable artery blockages, new blood vessels often sprout, routing blood around the obstruction, Hochman says. This improved circulation may not allow peak exercise, she says, "but in most of the activities of daily living it is sufficient to provide blood flow."
But this network of blood vessels disappears when a blocked artery is opened with a stent. Should the stent fail — as sometimes happens — Hochman says, "patients actually have another heart attack or they die when the artery suddenly closes and they're no longer protected immediately with that blood flow from the other arteries."
So why are stents so popular? "There's a pretty strong belief that an open artery is good," Hochman says. "These beliefs die hard."
Patient expectations also play a role. "A lot of them say, 'The artery's closed. I want it open,' " she says. A doctor also might perform an unneeded angioplasty to forestall allegations of negligence should the patient die, she adds.
Chan thinks primary care doctors have become more aggressive in referring patients with a few risk factors to cardiologists, who are primed to act. The cardiologist might implant a stent simply to avoid contradicting the referring doctor, Chan says. Meanwhile, in a fee-for-service system, doctors are paid for the procedures they perform. "I think there's no incentive to self-regulate," Chan says.