Heart Recoil

When a man starts worrying about his heart, he must literally put himself in his doctor's hands. For the diagnosis of heart disease still depends as much on a doctor's manual skill as on his instruments. The doctor feels a patient's pulse, listens to the rhythm of his heartbeat, estimates his blood pressure, measures his heart through X-ray pictures, and records on a graph the electric currents which result from its contraction.

Such detective work is not precise enough for Professor Isaac Starr of the University of Pennsylvania. Says he: "The function of the heart is to pump blood, and an engineer investigating a pump which was not working properly would ... begin by estimating the output of the pump directly."

Last week Dr. Starr told the National Academy of Sciences meeting in Philadelphia about an ingenious device: a balancing table, called the "ballistocardio-graph." A bed-size table is suspended from the ceiling on wires, three feet above the floor. While a patient lies quietly, the table oscillates back & forth to the throb of his heart.

When his heart contracts it throws a load of blood forward toward his head. "For the same reason that a discharged gun kicks one in the shoulder," said Dr. Starr, "the recoil throws the body feet-ward." An instant later, when the blood strikes the aortic arch (curve in large heart artery), "[the blood's] headward movement is arrested, creating an impact which throws the body and the table headward."

A normal man pumps about 14 quarts of blood a minute, moves the bed back & forth about 16 one-thousandths of an inch with every heartbeat. Connected to a powerful spring at the foot of the table is a tiny mirror. The mirror amplifies this motion 8,000 times. The magnified motion is recorded on a moving photographic film.

Because the jellylike body tissues tremble for a brief instant after every "blow" from the heart, after-vibrations warp part of the record. Hence Dr. Starr believes that his machine will never attain "highest precision." Nevertheless it is good enough to: 1) detect early, hitherto invisible cases of heart disease; 2) show the relation between high blood pressure and heart function; 3) differentiate between various types of heart disease.

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