Apart from the natural concerns about President Bush's health, the episode of abnormal heart rhythm that began during his Saturday afternoon run at Camp David may have struck fear in the hearts of other joggers: Can it happen to me? And is it likely to lead to sudden death?
The answers, from experts in heart disease, are "yes" to the first, and "no" to the second.
"If the heart is normal, atrial fibrillation is benign, short-lived and doesn't hamper the ability to do normal activities and go back to exercise," says Dr. Rick Veltri, director of cardiology at Sinai Hospital.
"One has to be concerned that there is perhaps an underlying ailment in the heart muscle or a heart valve; it can be a harbinger of something more serious," Dr. Veltri says. "But in a well-trained athlete, it normally is not."
Characterized by abnormally rapid, irregular and ineffectual contractions of the upper chambers of the heart, atrial fibrillation can occur in anyone -- the athletic and the sedentary, men and women, people who are resting or exerting themselves. Although it is more common in the elderly, it can occur in young people, too. It is unpredictable, and unpreventable.
The precipitating factors, in addition to heart disease, can include thyroid disease, an alcohol binge or a very large, very cold drink swallowed right after overheating during an exercise session, according to Dr. Sidney Gottlieb, director of the Henry Ciccarone Center for the Prevention of Heart Disease at Johns Hopkins Hospital.
Or, Dr. Gottlieb adds, "It just comes up, for no explained reason."
Sometimes the only symptom is a vague feeling of unease: "You feel funny or dizzy. You know something is wrong, but you might not be able to put your finger on it right away," says Dr. Raymond Bahr, director of the Paul Dudley White Coronary Care System at St. Agnes Hospital.
Another possibility, he continues, is that "you could pass out. [Fainting] is very common, especially with older people."
Exercisers, who are accustomed to the rapid heartbeat and pounding pulse that goes along with intense activity, might or might not notice something "a little different" about the way their heart is pounding, according to Dr. Veltri.
"Because the heart is going in a chaotic, irregular way in fibrillation, people get the sensation that it is racing more than usual," he says. "They may be short-winded or lightheaded at levels of exercise where they would otherwise feel just fine."
In some people, a single episode -- which ends by itself or with the help of medication -- is all there is. In others, the fibrillation becomes chronic or recurrent, which is more worrisome.
"When the atrium is in a normal contracting pattern, it is squeezing rhythmically. In fibrillation, the upper chamber flutters instead, and blood clots can form," Dr. Gottlieb warns. A clot, traveling out of the heart and through the circulatory system to the brain, can cause a stroke. So for people who go in and out of VTC fibrillation, doctors generally prescribe anti-coagulants (drugs that prevent clotting).
"In general, atrial fibrillation is not a real emergency," Dr. Gottlieb says. "But if your heart is going really fast, you may develop chest pains or other problems. And for certain patients with pre-existing heart disease, it can be an emergency."
That's one of the reasons physicians recommend a thorough check- up before starting an exercise program for people who have heart disease or the risk factors for heart disease, and for people who are past 35 or 40, the age at which heart disease begins to show up.
And, they say, if symptoms of arrhythmia do occur during activity, you should slow down, sit down and try to determine what is happening.
"If your normal heart rate while running is 140 or 150 [beats per minute], and you suddenly get this feeling and find it is going at 170, slow down, walk, then sit and rest," Dr. Bahr advises. "Usually, in about 15 minutes, your heart rate will come down under 100. If it stays up, you know something is wrong. Go to the emergency room to have it checked."
Dr. Veltri adds, "Obviously, if you are not feeling well, if you are lightheaded and about to pass out, you have to summon help. If you are out in the field, with no one around, the only thing to do is lie down and elevate your legs."
That's to get the blood flowing from your legs toward your upper body and reverse the lightheadedness, he explains.