Increased dispersion of ventricular repolarization and ventricular tachyarrhythmias in the globally ischaemic rabbit heart

Abstract

Contemporary concepts of ischaemic ventricular tachyarrhythmias (VTA) are based on increased electrophysiological heterogeneity of the myocardium. We developed a multi-site monophasic action potential recording system for an isolated rabbit heart to study the effects of global ischaemia on the electrophysiological properties at different ventricular sites simultaneously. The hearts were paced from the right ventricle (RV) andconduction time (CT), action potential duration (APD) and total repolarization time (TRT= [CT + APD]) were measured during normal perfusion and ischaemia. The dispersion of these parameters was calculated as the maximal difference between simultaneous recordings. Inducibility of VTA by programmed extrastimulation (ES) was investigated under normal and ischaemic conditions. During global ischaemia, CT increased progressivey showing a faster and greater increase at the left ventricle (LV) than at the RV. After 10 min the prolongation of CT reached a plateau at the LV while it continued to rise in the RV. The dispersion of CT increased from 14 ± 2.7 ms during normal perfusion to a maximum of 79.8 ± 17.2 ms after 14 min of ischaemnia (PPPPPP = 0.0001). The present results show that global ischaemia results in considerable electrophysiologic heterogeneity in the intact heart. These changes may be regarded as a suitable basis of VTA, induced by ES.