Simultaneous Measurement of Total and Nutritional Coronary Blood Flow in Dogs

Abstract

Significant correlation has been shown between the severity of coronary disease and level of coronary blood flow as measured by the rubidium coincidence technique. Contrary to the commonly expressed view, however, the rubidium coincidence method does not evaluate nutritional flow, but estimates total coronary blood flow (CBF T ). An equation is derived that does evaluate nutritional flow (CBF N ), allowing simultaneous measurement of total and nutritional flow. The extraction ratio of the total body (ER TB ) relative to the extraction ratio of the heart (ER C ) was measured in a total of 21 dogs by employing the relative uptake of labeled microspheres and diffusible ions, 86 Rb and 131 Cs. CBF T , measured with a bolus injection of 86 Rb or 131 Cs, was compared with total flow measured by the microsphere technique in dogs, with and without drug administration (norepinephrine, isoproterenol, nitroglycerin). These studies showed that while rubidium gives accurate mean values of total flow (4% mean difference, r = 0.92) individual estimates may be in error by as much as ± 42%. It was found, however, that isotopes of cesium are not suitable for measuring either total or nutritional coronary blood flow by the methods described in this paper. Comparison of CBF N with CBF T showed that not only was CBF N significantly less than CBF T , but the percentage increase in CBF N was significantly less than that of CBF T after norepinephrine or isoproterenol administration.