Newer agents for coronary thrombolysis. Perspectives from clinical studies

Myocardial infarction (MI) is a major cause of morbidity and mortality in western countries and the formation of intracoronary thrombi is recognized as a critical determinant of this ischaemic event. Since streptokinase and urokinase cause in vitro lysis of clots, it was though that these drugs were also effective in vivo in dissolving coronary thrombi. Clinical studies supported this concept. However, the beneficial effects of these drugs were, to some extent, offset by their inherent adverse reactions. Therefore new thrombolytic agents were developed, and for three of them (APSAC, tPA and proUK) there are enough clinical studies to allow for a comparison with 'old' agents. The data show that none of the new agents is safer or better than old agents with respect to easy handling, incidence of reperfusion of occluded coronary arteries, frequency of reocclusions, thrombus specificity, and bleeding complications. Thus, several directions are currently pursued to develop newer thrombolytic drugs with risk/benefit ratios better than those of 'old' agents. In this respect, it has been shown recently that the combination of aspirin with streptokinase is significantly better than streptokinase alone as far as mortality and incidence of rethrombosis is concerned. These data suggest that thrombolytic approaches safer and better than those currently available are possible and indicate that some of such new strategies are already available to enter the 'thrombolytic era' of acute MI.