EFFECTS OF REPERFUSION ON ARRHYTHMIAS AND DEATH AFTER CORONARY-ARTERYOCCLUSION IN THE RAT - INCREASED ELECTRICAL STABILITY INDEPENDENT OF MYOCARDIAL SALVAGE

Objectives. This study sought to delineate salvage dependent from salv age-independent coronary reperfusion in acute myocardial infarction an d the effects on spontaneously occurring arrhythmias and arrhythmic de ath in rats. Background. Reperfusion of the infarct related artery mig ht increase electrical stability independently of salvage of ischemic myocardium. Methods. In 98 conscious rats the electrocardiogram was mo nitored by telemetry for 48 h after MI, and all episodes of ventricula r tachycardia (VT) and ventricular fibrillation (VF) were analyzed. Re perfusion at 45 min (RP45) (n = 15), 90 min (RP90) (n = 18) and 180 mi n (RP180) (n = 30) min was compared with permanent coronary artery occ lusion (CAO) (n = 35) with respect to the post-reperfusion periods. Re sults. RP45, RP90 and RP180 reduced the incidence of VT by 93%, 98% an d 88% and VF by 89%, 97% and 92%, respectively (all p < 0.01 vs. CAO). The all-cause mortality rate was reduced from 47% (CAO) to 8% (RP45, p < 0.05) and 0% (RP90, p < 0.01); after RP180 it was 17% (CAO 42%, p = 0,08), All reperfusion regimens reduced arrhythmic deaths: 47% to 8% (RP45, p < 0.05), 47% to 0% (RP90, p < 0.01) and 42% to 8% (RP180, p < 0.05). Infarct size was identical to that during CAO (49 +/- 10% [me an +/- SD]) and RP180 (49 +/- 10%), whereas preferentially epicardial salvage occurred at RP45 (36 +/- 8%, p < 0.001) and RP90 (38 < 10%, p < 0.001). Conclusions. Early and late reperfusion reduce the incidence and duration of VT and VF in conscious rats with acute MI. Thereby, a rrhythmia-related mortality is improved through the prevention of fata l VE episodes. Thus, reperfusion increases the electrical stability of the heart independently of myocyte salvage, as proposed by the open a rtery hypothesis. (C) 1998 by the American College of Cardiology.