Effect of Nitroglycerin and Arterial Hypertension

This study was designed to evaluate the effects of nitroglycerin and phenylephrine-induced arterial hypertension on regional myocardial blood flow in awake dogs with acute occlusion of the left circumflex coronary artery. Myocardial blood flow to four transmural layers from epicardium to endocardium was estimated with 7-9 micron radionuclide labeled microspheres in 1) the nonischemic myocardium, 2) the central ischemic zone, and 3) the border zone separating ischemic from normally perfused myocardium. Measurements were repeated 1) during infusion of nitroglycerin, 0.015 mg/kg/min, 2) during phenylephrine administered to increase arterial pressure 60 mm Hg above the control measurements, and 3) during combined nitroglycerin and phenylephrine administration. Both nitroglycerin and phenylephrine increased myocardial blood