Hemodynamic Mechanisms of the Effect of Nitroglycerin in Patients with Acute Myocardial Infarction

We studied the hemodynamic response to intravenous nitroglycerin (NTG) in 40 patients with and without acute heart failure (hemodynamic subsets I-IV) during acute myocardial infarction. Hemodynamic measurements were performed by right heart catheterization. The results showed that NTG response influenced mainly the preload and to a lesser extent the afterload, however these changes were dependent on initial hemodynamic status. The changes in mean arterial pressure and cardiac index were predominantly related to pretreatment pulmonary wedge pressure and slightly to systemic vascular resistance. Response to NTG could be predicted with 85% probability as a decrease of pulmonary wedge pressure, with 58% probability as a decrease in mean arterial pressure and cardiac index, and with 32% probability as an increase in cardiac index and a decrease in systemic vascular resistance. These results indicate that NTG therapy could have optimal results in patients with elevated pulmonary wedge pressure and normal cardiac index, while in the subsets with low mean arterial pressure or low cardiac index potentially deleterious decrease in these values could occur. Therefore the optimal condition for use of intravenous nitroglycerin in the patients with acute heart failure is isolated pulmonary congestion.