Measurement of coronary blood flow using radioactive iodine compared with nitrous oxide.

Q measurement of coronary blood flow by indicator-dilution methods has been attempted by various groups within the past five years. The theory upon which these studies have been based is that after injection into either the pulmonary artery or left ventricle, the first activated blood to reach the right ventricle on recirculation returns by way of the coronary vessels. Henly and eo-workers rapidly injected a bolus of I human serum albumin into the distal pulmonary artery and monitored the curves in the right side of the heart. The resulting calculations gave coronary-flow values averaging less than 5 per cent of the cardiac output. No standard was used for comparison. Precordial counting to approximate coronary blood flow has been investigated by Love and Burch and compared with a direct method of measuring the blood emptying from the coronary sinus, using an infusion of the radioactive tracer. Two questions have been raised: (a) Is it