Reperfusion arrhythmias after thrombolysis. Electrophysiologic tempest, or much ado about nothing. Arrhythmias that may accompany myocardial reperfusion have generated significant clinical interest. First, there were concerns, based on animal studies, that high-grade ventricular tachyarrhythmias would pose a serious threat following thrombolytic therapy to treat an evolving myocardial infarction. Second, lower-grade arrhythmias, such as accelerated idioventricular rhythm, were cited as useful, noninvasive markers of successful reperfusion. Critical review of the current data, however, indicates that arrhythmias following thrombolytic therapy for acute myocardial infarction are usually neither dangerous clinical events nor consistent markers of reperfusion. 