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Mending Broken Hearts (part 1)

Cod. A07072007

By Jennifer Kahn
Foto: Robert Clark

As heart disease reaches epidemic proportions worldwide, researchers are moving away from the old "clogged-pipes" model to search for triggers lurking in our genes.

Cheeseburgers, smoking, stress, the rise of the couch potato: These are the usual suspects on the list of risk factors for heart disease, a malady reaching global epidemic proportions. Now discoveries about genetic triggers may help us spot trouble before it starts.

Gloria Stevens is lying on her back, sedated but alert, staring at an image of her own beating heart. Metaphorically, Gloria's heart is the very core of her emotional self—not to be worn on the sleeve, much less displayed on an overhead monitor. More literally, it is a blood-filled pump about the size of a clenched fist whose rhythmic contractions have kept Gloria alive for 62 years, and with a little tinkering will keep her going for an indeterminate number more.

At this moment, her doctor is threading a thin catheter up through her femoral artery from an incision in her groin, on into the aorta, and from there into one of the arteries encircling Gloria's heart. At the tip of the catheter is a small balloon. The doctor gently navigates the tip to a spot where plaque has narrowed the artery's channel by 90 percent. With a quick, practiced movement he inflates the balloon to push back the artery wall, deflates the balloon, then inserts an expandable stent—it looks like a tiny tube of chicken wire—that will keep the passage open. As Gloria watches on the monitor, the crimp in her artery disappears, and a wide laminar flow gushes through the vessel, like a river in flood.

The procedure is over. It has lasted only half an hour. In all likelihood, Gloria will be able to go home the next day. So will a few thousand other patients in the United States undergoing such routine angioplasty—more than a million of them a year. Pipe fixed, patient cured, right?

Wrong.

Because of her treatment, Gloria's quality of life will likely improve. She'll breathe easier and maybe live longer. But she is hardly cured. Her coronary atherosclerosis—a hardening and narrowing of the arteries that supply the heart with oxygen-rich blood—still leaves her vulnerable to future blockages and coronary heart disease.

Although hearts suffer many maladies—valves leak, membranes become inflamed—coronary heart disease, which can lead to heart attack and ultimately to heart failure, is the number one killer of both men and women in the United States, where 500,000 die annually. Worldwide, it kills 7.2 million people every year. Exacerbated by the export of Western lifestyle—motorized transport, abundant meat and cheese, workdays conducted from the comfort of a well-padded chair—incidence of the disease is soaring.

To help stem this lethal tide, cardiologists can prescribe such cholesterol-lowering drugs as statins to help keep arteries clear. They can advise patients to change their habits, or they can operate to fix an immediate problem. Angioplasty is one procedure, and surgery to bypass the diseased arteries is another—each year more than 400,000 bypasses are performed in the U.S. Transplants can replace severely damaged hearts, and artificial ones can keep people alive while they wait for a donor heart. But in the face of an impending global epidemic, none of these stopgap measures addresses the essential question: Who gets heart attacks and why?

The human heart beats 100,000 times a day, propelling six quarts of blood through 60,000 miles (97,000 kilometers) of vessels—20 times the distance across the U.S. from coast to coast. The blood flows briskly, surging out of a ten-ounce (0.3 kilograms) heart so forcefully that large arteries, when severed, can send a jet of blood several feet into the air. Normally the relentless current helps keep blood vessels clean. But where an artery bends, tiny eddies form, as in a bend in a river. This is where bits of sticky, waxy cholesterol and fat can seep into the artery wall and oxidize, like butter going rancid. Other matter piles up too. Eventually, the whole mass calcifies into a kind of arterial stucco, or plaque.

Until recently, cardiologists approached heart disease as a plumbing problem. Just as mineral deposits restrict the flow of water through a pipe, an accretion of plaque impedes the flow of blood through an arterial channel. The more crud in the system, the greater likelihood that a dammed artery will trigger a heart attack. Doctors now dismiss this "clogged-pipes model" as an idea whose time has passed. It's just not that simple.

Most heart attacks are caused by plaque embedded within the artery wall that ruptures, cracking the wall and triggering the formation of a blood clot. The clot blocks the flow of blood to the heart muscle, which can die from lack of oxygen and nutrients. Suddenly, the pump stops pumping.

Contrary to the clogged pipes model, heart attacks generally occur in arteries that have minimal or moderate blockage, and their occurrence depends more on the kind of plaque than on the quantity. Scientists have been struggling to figure out what type is most responsible. Paradoxically, findings suggest that immature, softer plaques rich in cholesterol are more unstable and likely to rupture than the hard, calcified, dense plaques that extensively narrow the artery channel. But understanding the root cause of the disease will require much more research. For one thing, human hearts, unlike plumbing fixtures, are not stamped from a mold. Like the rest of our body parts, they are products of our genes.