The right and wrong way to think about heart attacks.
Medicine brims with analogies and puns related to plumbing. Residents routinely refer to urologists as members of the "Stream Team," and cardiologists frequently say they're going to "Roto-Rooter" blocked coronary arteries. The comparison sometimes extends further: One cardiologist lobbying for better Medicare payments complained to a congressional committee, "I get paid less for a heart catheterization than a plumber gets for working on your pipes."
Yet the plumbing analogy causes serious confusion regarding heart disease, and as a result, we've wasted a lot of time and money on cardiac angioplasty that does no good. Consider the recent New England Journal of Medicine study documenting the failure of this method to prevent heart attacks and save many lives, along with the U.S. Food and Drug Administration's warning that drug-coated stents occasionally can cause the heart attacks they're supposed to stop.
It turns out there's a right and wrong place for the plumbing analogy. It's right for people who have heart attacks that involve a sudden, total blockage of a coronary artery. That's why procedures to unclog arteries with expandable stents and balloons ("angioplasty") save lives in emergencies and need to be used more in that setting. But the plumbing analogy fails when applied to stable, partial blockages that don't lead to sudden heart attacks. And yet doctors can't let go of the plumbing talk, and they keep unclogging partial blockages. That's why the vast majority of angioplasties are done for the wrong reasons—that is, for prevention, not acute treatment.
What's the source of this confusion? Like any organ, the heart needs a source of blood flow, and like any dictator, it looks after its own needs first. Thus, the first vessels emerging from the aorta are the coronary arteries, which divide to form an intricate lattice that supplies every muscle cell of the heart. In a heart attack, sudden blockage of the coronary arteries interrupts oxygen flow, which causes acid buildup that kills heart muscle within minutes. That's why a heart attack is rightly considered a plumbing emergency, and the best option is to unclog the artery.
Before angioplasty became widespread, the only emergency treatment for heart attacks was to infuse clot-busting drugs like streptokinase into a patient's whole body. This was like running concentrated Drano through a city's water supply to fix a stopped-up sink. It wasn't very effective and also caused side effects like bleeding. In 1929, a budding German crackpot named Werner Forssmann took the first tentative steps to directly unclog blocked vessels, by inserting a urinary catheter deep into his own arm. (A nurse tried to stop him, but he tied her to an operating table.) Forssmann walked up a flight of stairs and took an X-ray showing that the catheter had entered his heart—a feat that earned him the Nobel Prize.
Fifty years later, on his kitchen table, Andreas Gruntzig of Zurich invented a saline-inflatable, sausage-shaped balloon that could be threaded through blocked blood vessels, and reported the first "balloon angioplasty" of a blocked coronary artery in the New England Journal of Medicine. This technique was far more effective than clot-busting drugs and successfully unclogs arteries in more than 90 percent of cases.
Then, in the early 1990s, cardiologists widely began using stents, or wire-mesh tubes vaguely like Chinese fingercuffs, to prop open arteries, as studies showed they more reliably held open vessels than balloon angioplasty alone. By 1999, 85 percent of all cardiac catheterizations involved stents. In 2003 and 2004, the FDA approved Cordis's Cypher stent and Boston Scientific's Taxus stent, which gradually leach medications that prevent repeat blockage and so are about 50 percent more effective than bare-metal stents. Each generation of therapy is progressively more expensive; a bare-metal stent costs about $700, but coated stents run $2,200. Today, about 1.5 million stents are implanted yearly in the United States at a cost of $6 billion, and almost 90 percent are coated.
Angioplasty works great for sudden, massive heart attacks—as one interventional cardiologist recently told the New York Times, "This adrenaline rush is why people like me go into cardiology." (Arguably the financial rush is also sweet, since the median salary for invasive cardiologists is roughly half-a-million dollars.)
And there's no question that better access to emergency angioplasty for heart attacks would save lives. The gold standard for an acute heart attack, according to the Institute for Healthcare Improvement, is a hospital "door-to-balloon" time of less than 90 minutes. But less than one-quarter of heart-attack patients receive any angioplasty at all, according to a past president of the American Heart Association. Part of the problem is that only about 25 percent of hospitals offer emergency angioplasty, and because of arcane Medicare rules, they have a financial disincentive to transfer patients with acute heart attacks to places that do.
But improving emergency access isn't the same as relying on angioplasty as the standard preventive approach for healthy people with a partial narrowing of blood vessels (which are often detected by routine stress testing or increasingly fancy heart scans). Here's the problem: Time and time again, studies repeatedly show that opening blocked arteries to prevent heart attacks in people with exercise-induced chest pain or stable blockages is, quite simply, pointless. The weight of evidence is staggering. Essentially no clinical trial shows that balloon angioplasty or stenting partially blocked coronary arteries prevents heart attacks, saves lives, or reduces the risk of other complications like strokes. The emergency plumbing model developed for sudden heart attacks has absolutely no role in prevention.
Darshak Sanghavi is Slate's health care columnist. He is chief of pediatric cardiology and associate professor of pediatrics at the University of Massachusetts Medical School as well as the author of A Map of the Child: A Pediatrician's Tour of the Body. Follow him on Twitter.
Illustration by Robert Neubecker.