Beneficial effects of enalapril on reperfusion arrhythmia and segmental contraction in anesthetized dogs

Left anterior descending (LAD) was occluded for 60 min followed by reperfusion in mongrel dogs. In control group (n=14), 6 dogs died of ventricular fibrillation after LAD occlusion, another 4 out of 8 died of arrhythmia after reperfusion. While in enalapril pretreated group (n=10) only 1 died after occlusion and none after reperfusion (p<0.05). Segmental shortenings (L) in both ischemic and normal areas were measured by ultrasonic crystals implanted in subendocardium and connected to sonomicrometer 120. Both end diastolic length (EDL) and end systolic length (ESL) were prolonged significantly in ischemic area, and in control dogs the ESL often surpassed that of EDL, implicates a passive protraction of ischemic area during systole. While in enalapril group, reduction of AL was significantly less than that in control group, indicating the improvement in segmental contraction during ischemia. Enalapril lowered the blood pressure, dP/dt-max and blood pressure×heart rate, hence reduced myocardial oxygen consumption, which might contribute partly to the mechanism of cardio-protection.