AJP - Heart and Circulatory Physiology, Vol 235, Issue 6 794-H802, Copyright © 1978 by American Physiological Society
Analysis of myocardial and total body integral extraction ratios of rubidium-86
P. F. McDonagh, A. F. Salel, K. A. Krohn, E. A. Rhode and D. T. Mason
Coronary blood flow (QM) measurement with radiorubidium (Rb) assumes that
Rb distributes to the myocardium in proportion to flow. This assumption is
correct if the integral myocardial Rb extraction ratio (ERM) equals total
body extraction (ERTB). A right-heart-bypass preparation was employed to
test the hypothesis that ERM = ERTB and to examine the determinants of Rb
extraction. Dogs were anesthetized with pentobarbital, and arterial,
coronary venous, and total body venous Rb concentrations were continuously
measured for 4 min after injection. We found that ERM (0.56 +/- 0.01) was
significantly less than ERTB (0.70 +/- 0.01), P less than 0.01 (n = 29) and
concluded that Rb did not distribute in proportion to flow. We do not
recommend this method for clinical use. ERM is flow dependent and ERRB is a
function of the total cardiac output and the distribution of cardiac
output. Before employing Rb in animal experiments, it is recommended that a
preliminary study be performed comparing flow measured with Rb to an
independent measure of blood flow.
