Purpose: To determine the effect of intravenous streptokinase on early mortality in patients with suspected acute anterior and acute inferior myocardial infarctions.
Data Identification: A literature search of English-language studies on the use of intravenous streptokinase in the treatment of suspected acute myocardial infarction for the period 1966 to 1989 using Medlars II and the bibliographies of relevant articles. In a number of instances, additional details on early mortality by location of myocardial infarction were provided by the authors.
Study Selection: Of 140 originally identified articles, 6 that specifically met our inclusion criteria were selected: randomized trials that used intravenous streptokinase in a dose of 1.5 million units, with or without additional agents, compared with a group that differed only by the absence of streptokinase. Trials were selected by review of the methods section without regard for the results.
Data Extraction: Data were extracted independently by two observers using specific methodologic criteria for infarct location and early mortality. After they conferred, the observers agreed completely on the data.
Results of Data Synthesis: Among the 9155 patients with suspected acute anterior myocardial infarction, the mortality rate in the control group was 17.4%. In contrast, patients treated with streptokinase had a 12.5% mortality. The mean risk difference was - 4.8% (95% CI, - 7.5% to - 2.1%) and the summary risk ratio was 0.72 (CI, 0.65 to 0.79). A total of 9650 patients with suspected inferior infarction had a mortality rate in the control group of 7.7%. The mortality for streptokinase-treated patients was 6.6%. The mean risk difference was - 0.8% (CI, - 1.8% to 0.2%) and the summary risk ratio was 0.87 (CI, 0.76 to 1.01).
Conclusions: Intravenous streptokinase clearly confers a protective effect against early mortality in patients with suspected acute anterior myocardial infarction. The magnitude of this effect is on the order of a 5% absolute reduction in risk of death by 21 to 35 days. For these patients, 21 need to be treated to save 1 additional life. For patients with suspected acute inferior infarction, the benefit of treatment on reducing early mortality is of smaller magnitude and less certain. These patients have an estimated absolute reduction of early mortality of approximately 1%, which would require treating 125 patients to save 1 additional life.