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.
Why not? Dr. Arthur Agatston, famed for creating the South Beach diet, sensibly points out that partial blockages in coronary arteries don't cause heart attacks. The trigger isn't bad plumbing—but something more akin to a land mine. People at risk of heart attacks have largely invisible cholesterol plaques throughout their arteries, which act, he says, like unpredictable "little bombs that blow up suddenly and cause a sudden and devastating blockage" in previously healthy-appearing areas.
Yet doctors and patients largely ignore the data. Last year, the American Journal of Cardiology reported that 85 percent of all balloon angioplasties and stent implants are done nonurgently for stable blockages. The trial just published in the New England Journal of Medicine confirms this monumental waste. So what does help? Drugs that affect the entire coronary system—and not angioplasty or stenting—prevent heart attacks in high-risk patients. For example, Lipitor helped reduce rates from 21 percent to 13 percent in one study.
But this raises another concern: Relying on widespread use of powerful drugs carries its own risks. Consider that estrogen-replacement therapy became common because of its supposed reduction of coronary "land mines." Not only did that turn out to be completely wrong—the drug actually increased heart attacks—but as the New England Journal just reported, widespread use probably bumped up breast cancer rates by about 10 percent. Thousands of women died needlessly.
And so, in the end, we return to the old standbys, better diet and lifestyle. It's worth remembering that the Nurses' Health Study in 2000 determined that 82 percent of all "coronary events" were avoided by five simple behaviors: not smoking, exercising for 30 minutes daily, eating healthily, maintaining normal body weight, and drinking a small amount of alcohol. Over a lifetime, these healthy behaviors are 10 times more effective than Lipitor in lowering heart-attack risk, and infinitely more sensible than widespread angioplasty.
Almost 70 years after cardiac catheterization was invented, a medical specialty called "behavioral medicine" has been created to help refocus the billions of dollars—and talented physicians—on strategies for improving diet and exercise habits. Patient incentives, such as lower insurance premiums for healthy lifestyles, may also help. And expanding insurance programs for preventive medical services, instead of simply paying for more angioplasty, might motivate doctors to spend more time on the behavioral-change counseling front.
Then there are small but populationwide changes, like New York City's recent drive to eliminate trans fats, which has roughly the same cardiac benefit as treating everyone with Lipitor, without the side effects and cost. With the aid of campaigns to reduce salt intake, Australia has reduced average blood pressure by about 1 percent to 2 percent, potentially preventing 15 percent of strokes and 6 percent of heart attacks. Last year, Arkansas helped stabilize childhood obesity rates with school-based body-mass-index screening.
These kinds of approaches deserve widespread adoption. Someday, maybe we'll figure that out, and the plumbing analogy will finally melt away.
Addendum, May 10, 2007
On Wednesday, the Journal of the American Medical Association released the results of SWISSI II, a European study suggesting that angioplasty can prevent heart attacks. The researchers found that angioplasty may have prevented two-thirds of heart attacks in very high-risk patients.
However, this trial was very small (only 200 subjects total), was not blinded, and enrolled only select people who'd had a heart attack in the prior three months without the benefit of emergency angioplasty. These findings apply to a small subset of people, and do not change my fundamental contention that the great majority of angioplasty for prevention is without benefit.