A heart attack is hard to miss when it is accompanied by crushing chest pain that radiates down an arm, a cold sweat, difficulty breathing, nausea and loss of bladder or bowel control.
Similarly, it is not hard to diagnose angina pectoris, the chest pain that comes when the heart muscle is deprived of oxygen during exertion or emotional excitement. But for millions of Americans coronary heart disease, follows a far stealthier course. They are the victims of “silent” —or symptomless— heart disease.
Although neither they nor their doctors know it, they often experience myocardial ischemia, a temporary shortage of oxygen-rich blood to part of the heart usually caused by blockages in the arteries.
This is exactly the problem that causes angina, but for them it is painless.
Many, in fact, have suffered heart attacks that caused permanent damage to heart muscle yet produced no noticeable symptoms or else produced symptoms so mild or unusual that they were easily mistaken for another less serious health problem.
About one-quarter of all heart attacks are not recognized when they occur.
Yet, cardiologists say, these people have heart disease as serious and potentially deadly as someone who cannot walk a flight of stairs without chest pain or who was hospitalized for weeks with an unmistakable heart attack.
Unless their coronary problems are recognized and treated, such people could suffer a sudden and possibly fatal heart attack.
Still others at risk know they have heart disease because their first heart attacks were properly diagnosed or they had typical angina pain.
But because they seemed to recover uneventfully and were able to resume all their former activities, they received no further treatment.
But about one-quarter of them experience silent ischemic episodes that place them at high risk of a second coronary attack.
These instances of interrupted blood flow to the heart can be electronically detected, even when they produce no symptoms.
They have been shown to occur under many circumstances, including while a person is doing mental arithmetic and other sedentary activities.

As recently as the early 1970s few doctors believed it possible to have serious heart disease without telltale symptoms.
But, through studies involving exercise stress tests and ambulatory monitoring of heart rhythms, cardiologists showed that silent ischemia was a reality and far more common than even the experts had guessed.
“In fact, ambulatory monitoring showed that 75 to 80 percent of ischemic attacks are silent,” said Dr. Peter Cohn, chief of cardiology at the State University of New York at Stony Brook.
Autopsies of people who died suddenly revealed that many had severe coronary disease and some had suffered earlier heart attacks that went undetected, he said.
Each year, about 350,000 Americans who had no symptoms die suddenly and are found at autopsy to have had extensive coronary disease.
Such was the case with A. Bartlett Giamatti, the late commissioner of baseball and former president of Yale University, who had no history of heart disease yet died suddenly of a heart attack at the age of 51.
Had he undergone an exercise stress test, his silent heart disease would have become apparent and treatment might have saved his life.

In the last decade, researchers showed that patients without pain or other symptoms were not less sick or less likely to die than comparable patients with crippling angina pain.
A year-long study by doctors at Johns Hopkins Medical School of 103 patients who recovered from heart attacks revealed that those who had silent ischemia after-ward were three times more likely to die than were coronary patients who were free of ischemic episodes.