STUDIES ON THE CORONARY CIRCULATION

Abstract

Methods used were: (1) perfusion of an isolated beating heart by arterial blood from a donor dog; (2) perfusion of the beating heart, in situ. Simultaneous samples of ingoing arterial blood and outcoming coronary venous blood were analyzed for lactic acid, glucose, CO2 and O2. Coronary volume flow of blood was recorded. Perfusions were carried out for 30-90 min. with blood samples at 5-9 min. intervals. In 5 exps. on the isolated heart with a total of 53 pairs of samples, the average absorption of lactic acid was 1.5 mgm., of glucose 0.2 mgm., and of O2 3.5 cc. per gm. heart muscle per hr. Coronary flow was 42-55 cc. per gm. per hr. In 7 experiments with the heart intact within the open thorax, in 65 samples, lactic acid absorption was 3.1 mgm., glucose 0.39 mgm., and O2 5.1 cc. per gm. heart per hr. Mean coronary flow was 49 cc. In the first group, the R.Q. was below 0.70 in 3 and above 0.70 in 2 observations. In the latter group an R.Q. below 0.70 occurred in but one exp. The results indicate that glucose is absorbed in but small amounts by the heart, while lactic acid is removed from the coronary arterial blood in quantities which suggest its utilization as the carbohydrate fuel of the heart. The significance of the R.Q., glycogen of the heart and the results of other investigators in this field are discussed.