Interpolated extra-systoles,of frequent occurrence,in an otherwise normal human heart

Abstract

In the extensive literature upon extra-systoles about twenty writers have described the type known as the interpolated beat of the ventricle. Although such beats have frequently been produced experimentally, their occurrence clinically is comparatively rare. 1 Almost without exception they have been observed in cases showing gross lesions of the heart. The present case is of interest because the interpolated contractions occur persistently and frequently in a heart which, aside from a slow sinus rhythm, is otherwise normal. It furnishes a striking example of an organ on the borderland between a physiological and a strictly pathological condition.

T., a Chinese student at Cornell University, is in good health. He is able to take vigorous exercise, such as running, tennis, etc. About two years ago a cardiac irregularity was discovered in his routine physical examination. Prior to that time he was wholly ignorant of any disturbance in his heart, and is at no time conscious of the heart's contractions. Polygraphic records have frequently been made during the past two years and the organ has been found beating normally on two occasions only, and but for a short time.

The tracings show extra-systoles of the ventricle which occur with considerable regularity on some days, but usually they appear at varying intervals. The normal rate of the dominant rhythm averages about 60. It may go as low as 50 during rest. The extra-systoles average about 35 per minute during rest and 45 after vigorous exercise. The ectopic beat follows the normal contraction by a period averaging 1/2 second. The pause following the extra-systole is variable; occasionally it is fully compensatory. The dominant rhythm is but slightly disturbed, as a rule. Often it is strikingly constant, and it is seldom more variable than the rhythm of many normal hearts.