BACKGROUND:

Angiographic studies in the acute stage of myocardial infarction have shown complete occlusion in 75-85 percent and subtotal lesions in the remaining cases. Evidence for spasm in acutely occluded arteries has been reported. However, the majority of pathological as well as intraoperative examinations have yielded thrombotic material at the site of complete obstruction. Indirect evidence of thrombotic material was provided by successful intracoronary thrombolysis in 80 percent of infarct patients with complete obstruction. There could be causative relationships between spasm, intimal damage and coronary thrombosis. Selective applications of spasmolytic and/or thrombolytic substances into occluded vessels enabled high local concentrations with doses that caused little or no systemic effect. Angiographic verification of the results of this pharmacotherapy would help to clarify the role of spasm and thrombus in the pathogenesis of the acute coronary occlusion.

Reperfusion in man has been achieved by coronary by-pass surgery in the acute stage of infarction. Follow-up angiography revealed significant improvement of left ventricular function. Intracoronary streptokinase infusion resulted in recanalization of acute coronary occlusion in 80 percent of cases within 20-30 minutes of infusion time. Reperfusion achieved by intervention angiography has been associated with improved local wall motion as well as improved left ventricular function. Improvement in left ventricular function depended on the duration of symptoms prior to reperfusion and on the presence or absence of collateral blood flow. Available data suggested that improvement was more likely to occur if reperfusion was achieved within 3-4 hours. However, since the majority of patients reached the hospital after greater than 4 hours of chest pain, study of functional changes following late reperfusion was of great practical significance.

DESIGN NARRATIVE:

The study was a randomized trial of myocardial reperfusion in acute myocardial infarction by selective intracoronary infusion of nitroglycerin and/or intracoronary infusion of streptokinase. The trial was single-blinded as to the interventional therapy; it was double-blinded as to the drug infused. The primary endpoint was the ejection fraction on the 10th day of intervention. Patients were assigned to one of four treatment arms: an intracoronary infusion of streptokinase; an intracoronary infusion of nitroglycerin; combined infusions of nitroglycerin and streptokinase; a control group receiving conventional therapy without acute catheterization. All patients underwent anticoagulant therapy with intravenous heparin followed by warfarin for three months. Patients were followed for a minimum of two years.