The Effect of Nitroglycerin on the Systemic and Coronary Circulation in Man and Dogs

The pharmacodynamics of nitroglycerin have been studied in dogs and man. In dogs, intravenous nitroglycerin (TNG) caused a decrease in left ventricular work, myocardial blood flow (MFB), and myocardial oxygen consumption, and no significant change in coronary vascular resistance. Intracoronary artery TNG in dogs caused an immediate increase in MBF and a decrease in coronary vascular resistance that persisted until arterial pressure fell. In man, sublingual TNG (0.4 mg.) caused a decrease in left ventricular work, MBF, and myocardial oxygen consumption, and no significant decrease in coronary vascular resistance in patients with and without arteriographically proven coronary artery disease. The injection of doses of 0.1 to 0.2 mg. of TNG directly into the coronary artery in man caused an immediate increase in MBF and a decrease in coronary vascular resistance in patients with and without arteriographically proven coronary artery disease. The hypothesis proposed for the mechanism of action of TNG in the relief of angina pectoris is first, a decrease in coronary vascular resistance due to its effect on the coronary circulation, and, secondly, a decrease in cardiac work due to its effect on the systemic circulation.