Measurement of Coronary Blood Flow in Dogs with Normal and Abnormal Myocardial Oxygenation and Function

Common left coronary blood flow was measured simultaneously by a recording rotameter and by the Rb86 chloride clearance method in anesthetized, open chest dogs, and compared over a wide range of flow rates and under conditions of both normal and abnormal myocardial oxygenation and function. Although the Rb86 clearance method reflected the same directional changes as metered flow, a systematic underestimate was found which ranged from 27% at ischemic flow rates to 54% at hyperemic rates. Myocardial extraction studies supported the view that coronary flow rate and the resultant time that the isotope was in the capillary bed was the major determinant of the underestimate by the Rb86 method even under conditions of myocardial hypoxia. It was concluded that the Rb86 method gave an accurate estimate of directional change in coronary blood flow but that the magnitude of the underestimate of actual flow limits its use as a quantitative index.