Studies on the nature of the repolarization process: XIX. Studies on the mechanism of ventricular activity

Abstract

The clinical significance of the T wave in representing the electrical recovery process of the ventricular myocardium is well known. This electrical phenomenon, however, has been the subject of much less basic research than other parts of the electrocardiogram. With the development, in recent years, of more reliable recording techniques and the introduction of an incubator in which animal experiments can be performed in a more physiologic medium, this study of the repolarization process of the heart muscle seemed justified. Abundant controversy and confusion have developed over the direction of repolarization through the ventricular wall on the basis of polarity of the T wave. T polarity was studied by means of minute plunge electrodes recording simultaneously at selected depths in the ventricular walls. Moreover, the time course of the electrical recovery process was examined by comparing analogous points of the T wave in simultaneous records from the myocardial surface and the under-lying subendocardium and from different surface points, and these results compared with the polarity of the T waves. Experiments were designed also to study (a) the effect of local thermal changes upon adjacent and remote regions of the heart, (b) the effect of primary T-wave changes upon secondary ones by superimposing thermal changes upon left bundle branch block, and (c) the effect upon the T wave of ischemia due to chronic obstruction of coronary arteries.