Reperfusion-induced arrhythmias: characterization studies with the globally ischemic rat heart

It has previously been demonstrated in the rat heart, in vivo and in vitro, with regional ischemia, that an asymmetric bell-shaped curve defines the relationship between the vulnerability to reperfusion-induced arrhythmias and the duration of the preceding period of ischemia. The present study sought to establish whether a similar relationship occurred with global ischemia and reperfusion. Using rats from three different sources (two British, one North American) it was observed that, when an appropriate duration of ischemia was selected, reperfusion was capable of eliciting a very high incidence (up to 100%) of ventricular fibrillation and ventricular tachycardia. In the first series of studies an asymmetric bell-shaped relationship was observed such that with reperfusion after 5, 10, 20, 25, 28, 30, 33, 37 and 45 mins 0, 8, 8, 8, 50, 58, 83, 33, 33 and 25% of hearts fibrillated, respectively (12 hearts per group). However, upon repeating the studies with groups of rats from other suppliers or different batches from the same supplier, different results were obtained. Thus, in some study groups a very high incidence of arrhythmia was observed with reperfusion after very short (7.5 mins) durations of ischemia and low incidences were sometimes obtained with reperfusion after 30 mins, a time which, in some study groups, elicited a very high (100%) incidence of severe arrhythmias. These results contrast strikingly with those obtained with regional ischemia where a highly reproducible profile for the incidence of arrhythmias is consistently observed.(ABSTRACT TRUNCATED AT 250 WORDS)