Effects of acute ischemia on repolarization heterogeneity across ventricular wall in intact canine

Objective To investigate effects of acute ischemia on repolarization heterogeneity across ventricular wall in intact canine. Methods With MAP recording technique,MAPs of Epi, Mid and Endo were recorded simultaneously by composite plunge-needle electrode across left ventricular wall in 10 canines in vivo during acute ischemia.Monophasic action potential duration at 90% repolarization(MAPD90) in three layers were measured, and other parameters were observed at same time. Results During acute myocardial ischemia, MAPD90 shortened remarkably in Epi and Endo while modestly in Mid. Difference of MAPD90 between Mid and Epi or Endo was significant(P0.05).TDR(transmural dispersion of repolarization)in three layers of ventricular myocardium increased. Ventricular tachycardia or ventricular fibrillation occurred in 4 dogs under condition of acute ischemia, but no malignant arrhythmia occurred in all dogs before acute ischemia. Conclusion Repolarization heterogeneity across ventricular wall increased significantly under condition of acute ischemia,it may be associated with genesis of ischemic ventricular arrhythmias.