Because of the controversy concerning the effects on myocardial ischemia of maintaining systemic pressure concomitant with administration of nitroglycerin, this study was undertaken of the actions of nitroglycerin, with and without simultaneous phenylephrine infusion, on coronary blood flow, myocardial energetics and left ventricular function in 17 patients with multivessel coronary artery disease. Five minutes after sublingual administration of 0.4 mg of nitroglycerin, mean arterial pressure, left ventricular filling pressure, cardiac index and coronary sinus blood flow were reduced (P < 0.05) from control values. With mean arterial pressure raised to control level with phenylephrine in 10 patients (Group I), values for coronary sinus blood flow, myocardial perfusion gradient, cardiac efficiency index and ratio of coronary sinus flow/cardiac output all increased (P < 0.05) compared with values in 7 patients receiving only nitroglycerin (Group II) and in patients receiving nitroglycerin before phenylephrine in Group I and with the values in 7 patients who received no phenylephrine. Left ventricular function and coronary vascular resistance were unchanged (P > 0.05) from control values by the addition of phenylephrine to nitroglycerin. Because myocardial oxygen extraction decreased while coronary sinus flow increased, the phenylephrine-induced increase in coronary flow was not due to augmented cardiac oxygen demands. Thus, preservation of systemic pressure concomitant with nitroglycerin enhances myocardial perfusion. From these findings, with greater nitroglycerininduced decreases in mean arterial pressure and coronary flow in patients with acute ischemia, it appears that phenylephrine with nitroglycerin may particularly improve myocardial energetics.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine