Cardiology: The Fickle Heart

• Share

Many a layman who has just had an electrocardiogram takes his doctor's verdict of "ECG normal" as an assurance of a long and healthy life. Cardiologists know better. The repetitive squiggles on the ECG paper are simply a graphic recording of the electrical impulses that signal the heart's contractions. While an ECG will reveal some types of heart abnormality, and specifically whether a man has recently had a heart attack, it has limited predictive value—a fact made dramatically clear in the case of Lyndon B. Johnson, then Majority Leader of the Senate, who had a severe heart attack in 1955 just the day after a routine checkup had yielded a normal ECG.

The usual ECG, taken with a patient supine in a doctor's office, shows what is supposed to be normal for those conditions: when the auricles contract there is a small upthrust called the P wave; this is quickly followed by a sharply spiking QRS wave as the ventricles contract; after a brief rest, there is a gently rising T wave before the ventricles get a fresh electric charge (see diagrams). What happens to the normal healthy man's heart when he gets up off the couch and goes about his daily activities?

Inverted Waves. Led by Dr. Lawrence E. Hinkle Jr., a team of Cornell University Medical College researchers persuaded volunteers to spend up to ten hours of the day wearing miniaturized tape recorders and with two electrodes taped to their chests. Played back at 60 times normal speed, their tape-recorded cardiograms were condensed into ten minutes, which made any abnormalities more apparent.

The ECGs of healthy young men contained several surprises. In almost all cases, the T wave shrank when the men simply got up from a sitting position. It did so again during mild exercise. Eating a heavy meal had the same effect as exercise, and walking upstairs immediately after eating intensified the changes. By afternoon, the heart rate averaged ten to 20 beats a minute faster than in the morning.

More surprisingly, one-third of the healthy men had more striking and largely unexplained changes. Merely standing up put a notch in their T waves or turned them upside down; so did a heavy meal, after which, walking upstairs flattened the ST segment or pushed it below the base line. The researchers wondered whether the phenomena reflected varying degrees of atherosclerosis. Healthy young women, their arteries protected by a normal supply of estrogens, supplied an emphatically negative answer. Dr. Hinkle reported to the American College of Physicians that the young women's ECGs seemed to be at least as variable as the men's, perhaps more so.

Highway Stress. ECG changes in patients with known heart disorders were more puzzling and in some cases downright alarming, reported Dr. Thomas Killip III. A man of 20 who had no evidence of clear-cut heart disease had complained for years of occasional palpitations and extra heartbeats, even at rest. While wearing his ECG recorder he drove from New York to Princeton. What appeared to the cardiologists as dangerous bouts of nonrhythmic ventricular action occurred while the man was apparently unaware of them and doing 60 m.p.h. or more on the New Jersey Turnpike. He is now on digitalis, said Dr. Killip, and is "living a completely normal existence"—presumably still driving the turnpike.