QRS COMPLEX DURING MYOCARDIAL ISCHEMIA - EXPERIMENTAL ANALYSIS IN PORCINE HEART

Although ST segment deflections were widely utilized as a means of assessing the degree of underlying ischemic injury, the relationship of QRS complex alterations to the ischemic process is poorly understood. In this study a beat-to-beat analysis of the QRS complex in terms of ventricular activation time and R wave voltage in the acutely ischemic porcine myocardium was made and the relationship of these responses to changes in the area of ischemic involvement, altered myocardial energy demands and plasma K+ concentration levels were analyzed. This biphasic sequence of QRS alterations in early myocardial ischemia is attributable to a progressive leakage of K out of the ischemic cells which in turn alters both the time-course and transmural pathway of the the activation process through the ischemic tissue. These changes are related to both inotropic state and the area of ischemic involvement.