Distribution of Blood Flow to the Canine Heart.

Abstract

For the purpose of quantitating intercoronary anastomoses and arteriovenous shunts a known quantity of radioactive glass microspheres either 20 or 50[mu] in diameter were injected into the coronary system of the dog heart. The heart was perfused at a physiological rate with oxygenated blood at 38[degree]C. With the assumption that spheres were distributed at arterial bifurcations in the same proportion as blood, the fraction which appeared in 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. For purposes of the present study tissue or capillary flow refers to flow via vessels 20[mu] or smaller. This includes all true capillaries (less than 12u) and capillary-like vessels (16-20u). 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 right and left ventricules. This flow diminished to approximately .30 cc/g/min. in the distribution of the left anterior descending artery after ligation of this vessel. Arteriovenous shunts account for 2-4% of total flow across the heart. The existence of coronary vessels 20u or greater which communicate with the left ventricular lumen is questioned.