STUDIES ON THE CORONARY CIRCULATION. VII. THE REMARKABLE RESERVE POWER OF THE HEART

Abstract

In 7 dogs all the major coronary arteries of the left ventricle were ligated. As many as 8 coronary arterial branches were ligated in 1 animal. By means of slow-motion colored pictures of these expts., it was possible to evaluate the amt. of myocardium that lost its power to contract. It was found that in dogs as little as 15% of the ventricle apparently is sufficient to maintain adequate systemic circulation. The greatly diminished blood supply to the myocardium, under the conditions of the expts. descr. above, was demonstrated by intraven. injn. of fluorescein and motion pictures taken in u.-v. light. It would appear that the Thebesian circulation supplied little or no blood under these circumstances. In one expt., the remaining contractile element was able to maintain an asphyxial rise of blood pressure from 100 to 200 mm. Hg. These observations may offer a possible reason for the development of cardiac dilatation and hypertrophy in diffuse coronary artery disease even in the absence of hypertension. They may also suggest a possible explanation for survival in the presence of occlusion of both major coronary arteries, and for the persistence of life in spite of widespread disease of the myocardium.