Hemodynamics and Coronary Flow Following Diltiazem Administration in Anesthetized Dogs and in Humans

Abstract

In this study, the systemic and coronary hemodynamic changes associated with the administration of diltiazem, a recent calcium antagonist, were evaluated in three different situations as follows: following a 200μg/kg intravenous bolus of the drug in 12 open-chest anesthetized dogs; following two successive intravenous infusions of diltiazem (15μg/kg/min and 30μg/kg/min), each for a period of ten minutes, in eight patients with angina pectoris investigated by coronary arteriography; and following a single oral dose of 120 mg of diltiazem in 17 patients undergoing hemodynamic monitoring in the coronary care unit after a recent myocardial infarction. Diltiazem was found to be a coronary vasodilator acting on the large coronary arteries and on collaterals. Its effects on myocardial oxygen requirements were variable; as a rule, the predominant effect was a drop in systemic vascular resistance or in heart rate. When systemic vascular resistance changed little, heart rate tended to decrease significantly; however, when systemic vascular resistance decreased notably, heart rate remained unchanged because of a reflex attempt to increase systemic blood pressure. Cardiac performance and left ventricular end-diastolic pressure were not affected and this lack of change in cardiac inotropism may confer an advantage to diltiazem over other calcium antagonistic drugs in patients with coronary heart disease. In this study, the systemic and coronary hemodynamic changes associated with the administration of diltiazem, a recent calcium antagonist, were evaluated in three different situations as follows: following a 200μg/kg intravenous bolus of the drug in 12 open-chest anesthetized dogs; following two successive intravenous infusions of diltiazem (15μg/kg/min and 30μg/kg/min), each for a period of ten minutes, in eight patients with angina pectoris investigated by coronary arteriography; and following a single oral dose of 120 mg of diltiazem in 17 patients undergoing hemodynamic monitoring in the coronary care unit after a recent myocardial infarction. Diltiazem was found to be a coronary vasodilator acting on the large coronary arteries and on collaterals. Its effects on myocardial oxygen requirements were variable; as a rule, the predominant effect was a drop in systemic vascular resistance or in heart rate. When systemic vascular resistance changed little, heart rate tended to decrease significantly; however, when systemic vascular resistance decreased notably, heart rate remained unchanged because of a reflex attempt to increase systemic blood pressure. Cardiac performance and left ventricular end-diastolic pressure were not affected and this lack of change in cardiac inotropism may confer an advantage to diltiazem over other calcium antagonistic drugs in patients with coronary heart disease.