The science of sudden cardiac arrest.

Journalists and politicians across the country were in shock Friday afternoon at news that Tim Russert, the prominent and beloved NBC correspondent, had collapsed and died suddenly of a heart attack in the network's Washington office. Russert had previously been been diagnosed with several risk factors for a sudden heart attack, including coronary artery disease and diabetes. But his death is still a sad reminder that cardiac arrest can strike anyone without warning—and that when it does, it is often fatal.




Sudden cardiac arrest accounts for 310,000 deaths in America every year, or 850 a day—more than those caused by breast cancer, lung cancer, stroke, and AIDS combined. But despite how common the condition is, doctors know little about what predisposes one person to it and not another. The National Institutes of Health is currently mounting a major study at 60 trial sites across the country to try and identify risk factors related to both genes and lifestyle, and will begin enrolling patients this week. For now, says Jeffrey Olgin, a cardiologist at the University of California, San Francisco, assessing risk is "a very, very difficult thing. I can't look at you and say you have a 10 percent chance of dying from this."

Doctors do know that a previous history of heart attacks is the most important risk factor. Vice President Dick Cheney, who has suffered four heart attacks, wears a pacemaker to ward off sudden arrest. Age and gender also play roles, and as a 58-year-old male, Russert was in high-risk groups; the average age for suffering sudden cardiac death is between 58 and 62. Other factors involved in all forms of cardiovascular disease—family history, smoking, diabetes, and obesity—can come into play. Russert had some of these too; he had been previously diagnosed with diabetes and and coronary artery disease, and his autopsy on Friday showed an enlarged heart. But doctors do not know which of these factors is most important in causing a sudden heart attack, or why. They also do not know if stress plays a role at all; the data is unclear. "Most of us do not think it is terribly relevant," says Steven Nissen, chair of cardiovascular medicine at the Cleveland Clinic and a past president of the American College of Cardiology. After all, he notes, "many people in this world have stressful jobs," and they don't all die of of heart attacks.

What is clear is that there are ways to lower one's risk of sudden cardiac death: eat healthy, exercise, don't smoke, and take aspirin or statins. The trouble, though, is that patients often don't think they're at serious risk until they are actually experiencing an attack. In about a third of all sudden deaths due to coronary disease, death is the first sign that anything major is wrong. Russert himself was exercising and taking medication for his coronary artery disease, which was asymptomatic. He performed well in a stress test two months ago.

A sudden cardiac arrest is, of course, unexpected, but the process that causes it may begin many years before. "In middle-aged men, it's virtually always caused by degeneration in the wall of a coronary artery," says Dr. Thomas Risser, a cardiologist at Cambridge Health Alliance. "It starts with fat deposits and inflammation, and these plaques just lie there silently." They can do so for decades until one of them fractures, at which point the body tries to plug the hole with a blood clot—and ends up blocking off the whole blood vessel. This condition is known as a coronary thrombosis, and it is extremely dangerous. The heart muscle, now starved for oxygen-rich blood, falls out of rhythm; it quivers but doesn't pump. "In the final stage, the ventricle looks like a bag of worms. It's chaotically beating very fast and therefore is completely inefficient at pumping blood," says Olgin. "Soon, there's no blood flow anywhere, including the brain, and people just suddenly collapse."

Once a patient's heart has gotten out of a normal rhythm, it can't get back on beat on its own. But a defibrillator—either an internally implanted one such as Cheney's, or an external one with electrical paddles—can get the heart beating steadily again, provided it is used in time. "If people get there with an external defibrillator within three minutes of a collapse, the survival rate for the kind of thing Russert may have had can be as high as 50 percent," says Robert J. Myerburg, a cardiologist at the University of Miami Miller School of Medicine. "But time is the whole issue. If you rely on fire/rescue teams to bring one, the chance of survival drops seven to ten percent" with every minute that passes after a collapse. It's unclear whether Russert had access to a defibrillator. His internist said on Friday that "resuscitation" had begun immediately after the collapse and continued at the hospital, to no avail.
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