Role of nitrates in acute myocardial infarction.

Management of patients after myocardial infarction includes several therapeutic options. Lysis of the coronary thrombosis with intravenous or intracoronary administration of streptokinase or intravenous administration of one of the newer, currently experimental agents, such as tissue plasminogen activation or prourokinase, can directly restore oxygen and substrate delivery to potentially salvageable myocardium. Percutaneous transluminal coronary angioplasty can likewise restore vessel patency with potential salvage of ischemic myocardium, if perfused sufficiently early after symptom onset. Another strategy is to administer intravenous thrombolytic therapy and then perform early angioplasty on patients with acute myocardial infarction who reach the hospital within 4 hours of symptom onset. These patients should have intravenous nitroglycerin begun before or simultaneously with beginning thrombolytic therapy. The infusion is titrated to lower systolic arterial pressure by 10% to 15%, and then maintained at a constant rate for up to 48 hours. Patients seen more than 4 hours after symptom onset, with evidence of viable myocardium (e.g., persistent R waves in those electrocardiographic leads demonstrating ST-segment elevation) may also receive intravenous nitroglycerin and thrombolytic or percutaneous transluminal coronary angioplasty therapy. The combined results of the several clinical trials of intravenous nitroglycerin in acute myocardial infarction would support its use in patients seen 4 to 12 hours after onset of symptoms or in patients seen earlier, in whom thrombolytic or percutaneous transluminal coronary angioplasty therapy cannot be utilized.