Tissue Blood Flow to the Heart

Regional tissue blood flow to the heart was measured in the dog using deuterium oxide as a tracer substance. The method assumes that the rate of uptake of the tracer by a tissue is limited by the blood flow through the tissue and that the exchange of the tracer between blood and the extravascular space in the organ is instantaneous by comparison. This assumption has had Previous confirmation. Six groups of animals were studied and the results revealed: (1) a uniform distribution of blood flow per unit of weight of tissue between the right ventricle and various parts of the left ventricle; (2) a decrease in tissue blood flow to (0.1 ml./Gm./min., or less), ap proximately 7 per cent of normal in the area supplied by the left anterior descending coronary artery after acute occlusion of this vessel; (3) a failure of two operative procedures designed to increase intercoronary anastomoses to influence this greatly de creased flow, when these procedures were performed six weeks to six months prior to testing; (4) an increase in tissue blood flow to an ischemie area of myocardium to 50 per cent of normal four to six months after coronary occlusion; (5) a failure of olerative procedures to increase significantly the blood flow to the ischemic area over that which developed naturally, indicating no additional collateral vessel development due to the operations. The results of this investigation were discussed in relation to experiments which deal with myocardial function and vulner ability to ventricular fibrillation after coronary occlusion.