Factors influencing the T wave of the electrocardiogram. An experimental study employing intracavitary and extraventricular (epicardial) leads: I. Effects of heating and cooling the endocardium and the epicardium

Abstract

The effects of cooling and heating the endocardium and epicardium have been studied by the use of intra- and extraventricular exploring unipolar leads. Direct evidence has been obtained that changes in the electrical state of the endocardial muscular lamina modify the form of the electrocardiogram. Changes in the T wave can be produced by changing the rate and order of endocardialepicardial laminar repolarization. Negative T waves occurred where the exploring electrode subtended areas which had relatively or absolutely retarded repolarization; positive T waves occurred where the exploring electrode subtended areas which had relatively or absolutely accelerated repolarization. It was found that negative T waves occurred: 1. A. In the cavity (1) when the endocardium was cooled; (2) when the endocardium was not altered, but the epicardium was heated. 2. B. On the epicardium or precordium (1) when the epicardium immediately under the electrode was cooled; (2) when the endocardium subjacent to the epicardial exploring electrode was heated; (3) when the endocardium of the opposite wall was cooled. It was found that positive T waves occurred: 1. A. In the cavity (1) when the endocardium was heated; (2) when the epicardium was cooled. 2. B. On the epicardium or precordium (1) when the subjacent epicardium was heated; (2) when the subjacent endocardium was cooled. The relation of these results to the modern concept of altered repolarization in an extensive conducting medium are discussed. The spatial relation of the exploring electrode to a theoretical surface at the junction of the normal and altered areas is used to account adequately for the findings. The practical value of these observations is discussed. The present results confirm and extend previous observations on the contribution of the subendocardial myocardium to the electrocardiogram.