Distribution of Blood Flow to the Canine Heart.

SummaryA known quantity of radioactive glass microspheres either 20 or 50 ± in diameter were injected into the coronary system of the dog heart being perfused at a known and physiological rate with oxygenated blood at 38°C. With the assumption that spheres were distributed at arterial bifurcation in the same proportion as blood, the fraction which appeared in the venous drainage was taken as a measure of arteriovenous shunts the size of or larger than the spheres injected. Those spheres which remained in the tissue provided a measure of flow through vessels smaller than the spheres. Since the spheres were small enough to pass through all arteriovenous shunts except capillaries, the radioactivity of the tissue was a measure of tissue capillary flow (less than 20 μ for the purposes of the present study). There was a uniform distribution of spheres in the normal dog heart. A calculated tissue blood flow of approximately 1.2 cc/g/min existed in the right ventricle and throughout the left ventricle. This flow diminished to approximately .30 cc/g/min in the distribution of the left anterior descending coronary artery after ligation of this vessel. Evidence is presented to suggest that arteriovenous shunts account for 2–4% of total flow across the heart and that these vessels are probably greater than 50 μ in diameter. No evidence for arterioluminal shunts 20 μ or greater in size communicating with the left ventricle was found.