Early thrombolysis and low dose aspirin reduce mortality from myocardial infarction by about 25%,1 and in combination the two drugs have an additive effect, reducing mortality by 45%.2 This reduction is maintained for up to 12 years after the event and the survival curves of placebo treated patients are parallel to those of the treated groups, showing that there is no additional long term effect of active treatment.2-4 The benefit is simply a reduced case fatality rate at the time of the event. In this paper we discuss a hypothetical explanation for these observational data, based on current understanding of the pathophysiological processes during infarction and the effects of reperfusion therapy.

Although postmortem examinations are limited, there is no single cause for the observed benefit but a general reduction in mortality and complications across the board.5-7 That infarct size is reduced by thrombolytic treatment is seen by cumulative measurements of cardiac enzyme release and left ventricular function is better in patients treated early.8-9 Most commentators have attributed the reduction in mortality to preservation of left ventricular function by early reperfusion by way of a number of theoretical mechanisms (table 1).10-12 However, the absolute difference in left ventricular ejection fraction between groups treated with placebo and those treated by thrombolysis is small.13 Moreover, mortality is reduced in patients treated late despite little evidence of a reduction in infarct size and …