[Late thrombolysis in the therapy of acute myocardial infarct: the prospects for its wide-spread clinical use].

Animal experiments and clinical observation in humans have established a window of opportunity during which reperfusion after acute myocardial infarction may salvage myocardium. This time window was initially thought to be 3 to 4 hours from the onset of coronary occlusion, but it has been recently recognized in humans to be longer, at least 6 hours and possibly even longer. The longer time span for effective intervention was determined in several studies showing an increased survival rate as a consequence of the improvement in left ventricular function and the reduction of infarct sequels with late thrombolysis. Main mechanism by which late thrombolysis may lead to survival benefit seems to be infarct-related artery patency. However, other mechanisms have been postulated such as the positive influence on remodeling, electric stability and different effects due to the breakdown of systemic fibrinogen and the anticoagulant effect that this can produce. Regardless of which of these proposed mechanisms is responsible for reducing mortality in patients treated with late thrombolysis after myocardial infarction, the limitation of treating patients only within the 4- to 6-hour time window must be seriously reconsidered.