Thrombolytic therapy in patients with acute myocardial infarction.

THROMBOLYTIC THERAPY in patients with acute myocardial infarction has received renewed attention since intracoronary infusion of streptokinase has been introduced into clinical practice. Efficacy of intracoronary infusion of streptokinase. In-tracoronary infusion of streptokinase results in recana-lization of approximately 75% of completely obstructed infarct-related vessels" 2 (table 1). Modifications of the technique, such as subselective infusion of strepto-kinase via small catheters, increased infusion rate, or injection of a bolus at the initiation of therapy, have not resulted in reproducibly higher recanalization rates3'-2 (table 1). The-influence of intracoronary infusion of streptokinase on ejection fractiom has been assessed in five controlled trials3, 4. 7, 8. 12 (table 2), but only Ander-son et al.4 found a significant improvement in left ventricular function from the acute to the chronic stage of infarction in patients treated with streptokinase. Lack of functional improvement in the majority of trials has been attributed to a delay of more than 4 hr between onset of infarction and commencement of therapy. However, Leiboff et al.8 found no improvement of function in patients treated with streptokinase, although therapy was initiated within 4 hr. This negative result may be related to the relatively high reocclu-sion rate in Leiboff's study. The published data suggest , but do not prove, that sustained early reperfusion may be associated with improvement of left ventri-cular function. Additionally, reperfusion after more than 4 hr may be beneficial in some subgroups of patients, as suggested by the functional improvement associated with infusion of streptokinase after 6 hr in our trial, although this finding was not statistically significant.'2 To test these hypotheses, a much larger trial is being conducted. Statistically significant improvement in mortality after infusion of streptokinase was reported in only one trial.7 The mechanism of improved survival in this study remains unclear, since there was no parallel increase in ejection fraction. Furberg'3 pooled the survival data of eight prospective randomized trials, including the one that showed significant improvement, and calculated a mortality of 11.0% in 382 patients treated with intracoronary infusion of streptokinase compared with 12.4% in 364 control patients; this difference was not statistically significant. The influence of intracor-onary infusion of streptokinase on mortality remains unknown. Complications associated with intracoronary infusion of streptokinase. Because of the high complication rates inherent in acute myocardial infarction, it is difficult to pinpoint those complications that are the result of early intervention. The intervention-related complication rates can be assessed only by randomized …