COMPARISON OF THE ELECTROCARDIOGRAPHIC CHANGES PRODUCED BY HEATING AND COOLING EPICARDIAL AND ENDOCARDIAL SURFACES OF THE DOG VENTRICLE

Abstract

In 18 dogs the influence on the T wave in the standard leads and precordial leads was studied, following warming and cooling of restricted areas of the endocardium and overlying epicardium of both the right and left ventricles. In all expts. the T wave changes so produced were the same, regardless of whether the endocardial or epicardial surfaces of a given region were warmed or cooled. Warming the endocardium and epicardium of the zone underneath the chest electrode (both in the right and in the left ventricle) produced sharp increase in the positivity of T; cooling this area produced inverted T waves. Warming areas at a sufficient distance from the exploring electrode produced opposite effects, namely, inversion of T regardless of whether the endocardium or epicardium was treated. In Lead III the effects of cooling or warming the endocardium in the right or left ventricle corresponded with results obtained from treatment of epicardial regions. Warming the anterior surface of the right ventricle endocardially of epicardially inverted the T wave while cooling increased it. Some septal and basal areas of the left ventricle give similar results. Cooling the posterior surface and apex of the left ventricle inverted the T wave whether the endocardium or epicardium was affected. Warmingthese regions elevated the T wave. The expts. lend no support to the theory that differences in rate of repolarization between epicardial and endocardial myocardium are responsible for the formation of the T wave.