Intravenous isosorbide-5-mononitrate in the treatment of acute myocardial infarction

Abstract

The action of isorsorbide-5-mononitrate (IS-5-MN) infusion (range 6.0 to 10.0 mg/hour) was studied in 24 patients with and without acute heart failure (hemodynamic subsets I to IV) during acute myocardial infarction. Hemodynamic measurements were performed by right-sided cardiac catheterization. Intravenous IS-5-MN demonstrated significant hemodynamic effects compared with baseline values. In subsets I and II, a decrease in pulmonary wedge pressure (PWP) and in cardiac index (CI), without significant changes in heart rate, mean arterial pressure or systemic vascular resistance index were demonstrated. In subsets III and IV, a major increase in CI and a decrease in systemic vascular resistance index, as well as a decrease in PWP were found. Again no changes occurred in mean arterial pressure and heart rate. The dosage was similar in subsets I to IV (8.0, 7.9, 7.8 and 7.3 mg/hour); thus, the differences in the responses could not be attributed to dosage. It appears that several different patterns of hemodynamic IS-5-MN action exist, assuming that IS-5-MN operates on preload and afterload levels. The action of IS-5-MN mechanisms seems to be dependent on an initial hemodynamic subset. No patient had any deleterious hemodynamic effects. A decrease in CI in subsets I and II was not of clinical importance with these dosages. No nitrate tolerance during 9.0 hours of continuous therapy appeared. The duration of the time needed to restore baseline values after IS-5-MN discontinuation demonstrated the following: a decrease in CI in subsets I and II lasting an average of 2.2 hours; a decrease in PWP in subsets II and IV lasting an average of 4.2 hours; and an increase in CI in subsets III and IV maintained at an average of 3.8 hours. No signs of a rebound hemodynamic phenomenon were found in any patient.