Regional Distribution of Myocardial Blood Flow in the Dog as Determined by Rb 86

The distribution of Rb 86 Cl in the canine myocardium was determined at 20 seconds, 10 minutes, and 19 hours after administration of isotope. The uptake of Rb 86 20 seconds after injection is related to blood flow, and the myocardial distribution of isotope probably closely reflects the apportionment of coronary blood flow. The isotope was uniformly divided between the various regions of the left ventricle and averaged 6.4 per cent of the injected dose per 100 Gm. of tissue. This value exceeded the fractional uptake of 4.3 per cent for the right ventricle and 3.7 per cent for the atria. After 19 hours, the Rb 86 content serves virtually as a tracer for potassium. After this interval, the myocardial distribution of Rb 86 closely followed previously published reports of the relative potassium contents of the various myocardial regions.