Action of Nitroglycerin on the Coronary Circulation in Normal and in Mild Cardiac Subjects

Nitroglycerin has been used extensively as a coronary vasodilator. Its remarkable clinical effect has been presumed to be related to a direct action on the smooth muscle of the coronary arteriole. No observations have been made of nitroglycerin action on the coronary circulation in man. This report presents studies of changes induced by the drug in 10 normal or nearly normal subjects. The authors present evidence that although coronary vasodilatation does indeed occur, it appears to be secondary to changes in myocardial oxygen requirements. Hemodynamic observations revealed a general decrease in pressures in both peripheral and pulmonary circuits; caution is urged concerning the occasional severe hypotensive effects of nitroglycerin.