Interventions that potentially limit myocardial infarct size: overview of clinical trials.

Theoretically, interventions that restore the balance between oxygen supply and demand when given during the early hours of a heart attack may reduce infarct size and prevent fatal arrhythmias and thereby prolong survival. Data on mortality from the available randomized trials of thrombolytic therapy, intravenous beta blockers, hyaluronidase, intravenous nitrates and calcium channel blockers in acute myocardial infarction, are systematically reviewed. Analyses confirm that intravenous streptokinase reduces mortality by about 25% but suggests that measures to prevent reinfarction may be required after thrombolytic therapy. beta blockers reduced mortality by approximately 15%. The pooled data from the existing trials of hyaluronidase and intravenous nitrates are consistent with a 15% to 20% decrease in mortality; ideally this should be confirmed in future large randomized trials. Currently, there is no evidence either from individual studies or the aggregate of all the trials that calcium channel blockers reduce mortality. The collective experience from the trials carried out over the last 2 decades suggests that most interventions in acute myocardial infarction have, at best, only moderate effects with a 10% to 20% reduction in mortality. Current and future trials that assess the effects of cardiovascular treatments on mortality should therefore aim to randomize 10,000 to 20,000 average risk patients or a few thousand high risk patients.