Effects of losartan on the electrical heterogeneity of ventricular wall during acute ischemia in canine in vivo

Objective:To explore the effects of losartan on the electrical heterogeneity of ventricular wall during acute ischemia in canine in vivo. Methods: In canine acute ischemic model, 16 dogs were divided into 2 groups, control group( n = 8) and losartan group( n =8). losartan (5 mg.kg-1.d-1 ) was administered for 2 weeks before operation. With monophasic action potential (MAP) recording technique , the MAPs in epicardium (Epi), mid-cardium and endocardium (Endo) were recorded simultaneously during myocardial ischemia in two groups. MAPD, transmural dispersion of repolarization (TDR) and arrhythmias were monitored. Results: During acute myocardial ischemia, MAPD90 was shortened remarkably in the Epi and Endo, modestly in the Mid. The difference of the MAPD90 between Mid and Epi or Endo was significant ( P 0. 05). TDR in the three layers of ventricular myocardium were increased. Ventricular tachycardia or ventricular fibrillation occured in 4 dogs under the condition of acute ischemia, but no malignant arrhythmia occurred in all dogs before acute ischemia. The TDR in the losartan group was smaller than that in the control group ( P0.05). No ventricular tachycardia or ventricular fibrillation was found in the losartan group, the difference of the rate of malignant arrhythmia was significant between the two groups. Conclusion:The results suggest that losartan can suppress the TDR in acute ischemic myocardium, and decrease the development of malignant arrhythmias.