Intervention in acute myocardial infarction

Abstract

The most critical substrate lacking in infarcting myocardium is oxygen and early reperfusion would appear to be the most promising approach to infarct reduction. The efficacy of thrombolytic therapy has been shown by an increase in the global ejection fraction assessed by angiography or gated blood pool techniques and also by a decrease of almost 50% in the radioisotope perfusion defect after 3 to 4 weeks. Functional results in a group of patients subdivided according to success of thrombolysis and plasma creatine kinase levels showed that, among patients with successful thrombolysis, those with the least ischemic damage had experienced shorter ischemic periods and had significantly more collateral vessels supplying the infarcting area. It is recommended that the ischemic period should not extend beyond 3 to 5 hours before therapy is begun. The combination of intravenous streptokinase followed by intracoronary streptokinase was found to lead to a significant shortening of the ischemic period when compared with intracoronary streptokinase alone. Reocclusion of the infarct vessel has been shown to occur in 10% to 30% of patients after successful reperfusion, especially in arteries with severe residual stenosis, but immediate revascularization caried out after reperfusion in such patients can bring about a substantial decrease in the 1 year mortality rate. Successful reperfusion showed particular benefit in patients with previous myocardial infarction in another area, in patients with large left ventricular perfusion defects and in patients with predominantly right ventricular infarction.