Cardiology: Quick Detective

No physician and no machine can forecast with certainty whether a man will have a heart attack, or when. Until such prevision becomes possible, doctors must rely heavily on the electrocardiograph, which, although not much of a predictor, is a smart detective. It can usually reveal whether a heart has been damaged, and with these clues the cardiologist can prescribe care and treatment for patients who seem to run the greatest risks of heart attacks. Yet the electrocardiograph has identified only a fraction of the nation's ailing hearts.

One reason is that the ECG is relatively expensive; each reading...