Effects of intracoronary nitroglycerin on coronary vascular volume in man, assessed by a double-indicator dilution technique.

The effects of 0.2 mg nitroglycerin administered directly into the left coronary artery were studied in 7 patients with coronary artery disease. A multipurpose catheter designed for simultaneous measurement of coronary sinus flow and great cardiac vein flow by thermodilution and for addition recording of dye dilution curves by a fiberoptic method was introduced from a right antecubital vein into the coronary sinus and advanced with its tip to the great cardiac vein/anterior cardiac vein juncture. Coronary sinus flow and great cardiac vein flow were measured using the constant infusion technique. Selective bolus injections of indocyanine green dye were measured using the constant infusion technique. Selective bolus injections of indocyanine green dye were performed into the left coronary system via a 8 French Judkins catheter and dye dilution curves were recorded in the upper great cardiac vein. From these curves, coronary transit time was assessed and coronary vascular volume was calculated as great cardiac vein flow times coronary transit time. Intracoronary nitroglycerin led to a transient drop in regional coronary resistance that was associated with an almost parallel increase in intravascular volume. Since this increase in coronary vascular volume exceeded the well-known dilatory effect on the epicardial arteries, and lasted slightly longer than the drop in regional resistance, these data imply that the vasodilatory action of nitroglycerin is different in magnitude as well as in time course in different parts of the coronary circulation.