The Nature of Normal and Abnormal Electrocardiograms: VIII. Relation of ST Segment and T Wave Changes to Intracellular Potentials

Introduction CHANGES in the T wave, as well as in the ST segment, are among the most important electrocardiographic aids in the diagnosis of angina pectoris, myocardial infarction, and other ischemic and nonischemic conditions. Nevertheless, the pathogenesis of the T wave changes has been very difficult to ascertain owing to the great sensitivity of the T wave to biochemical, biophysical , and other alterations of the myocardium. 1-3 Of the many previous experimental studies of T wave polarity and duration, 4-9 only one 9 that this laboratory is aware of has included simultaneous recordings of intracellular electrograms to demonstrate the membrane potential changes associated with the abnormal T waves. This problem was approached in the present investigation by application of electrographic techniques previously developed in acute myocardial ischemia. 10,11 The T wave changes were produced by perfusion of cooled or heated blood into the coronary artery.* Simultaneous surface and intracellular electrograms