A Heart's Hidden Danger

It

is not an uncommon story--a fit man in his 40s or 50s arrives at his doctor's office for his annual checkup and eventually leaves with a clean bill of health. Soon afterward he drops dead of a heart attack. Why didn't his tests show anything amiss? Cardiologists are increasingly convinced they have discovered the answer. Evidence is growing that not all the fatty deposits found in coronary arteries are equally prone to trigger heart attacks. Often the smallest, least detectable plaques are the most dangerous--because of their unhappy tendency to burst, triggering the formation of a clot that blocks a blood vessel.

Doctors attending the American College of Cardiology meeting in Atlanta last week presented data suggesting that as many as 80% of all heart attacks--not just the ones that seem to strike out of the blue--are caused by this so-called vulnerable plaque.

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To learn more about these deadly deposits and how they are changing the conventional wisdom on what causes heart attacks, I talked to one of the leading researchers in this field: Dr. Peter Libby, chief of cardiovascular medicine at Brigham and Women's Hospital in Boston. Libby and his colleagues compare the cross section of an artery to a doughnut with a hole--where the doughnut is the arterial wall and the hole is the space where blood flows. "In the past, we have studied just the hole," he says. So big plaques that appeared on the verge of plugging the hole looked mighty dangerous--and many of them are. But, Libby adds, "it is important to look at the doughnut itself."

Once doctors do that, they realize that there are two main types of plaque: hard and soft. The soft kind is the most vulnerable to rupturing without warning. But what makes soft plaque doubly dangerous is that it doesn't always protrude into the hole where the blood flows. Instead it is buried in the arterial wall--or doughnut--where it is harder to detect.

Some doctors are experimenting with ultrasound probes, which they thread through the arteries to try to locate this soft, vulnerable plaque. Others are looking at magnetic resonance imaging and other specialized scanning techniques that may highlight the presence of vulnerable plaque.

In the meantime, researchers are focusing on ways to make vulnerable plaque more stable. One promising possibility: the increasingly popular class of cholesterol-lowering drugs called statins, which seem to pull soft plaque out of fatty deposits wherever it is located in the artery, making it less likely to burst. Of course, it never hurts to quit smoking, eat right and make sure your blood pressure is under control, though, if you don't want your heart to surprise you.

Dr. Gupta is a neurosurgeon and CNN medical correspondent