An appraisal of the double indicator-dilution method for the estimation of mitral regurgitation in human subjects.

T HE shape of an indicator-dilution curve is determined by at least 4 variables: cardiac output, the volume between the injection site and the sampling site, the presence of a left-to-right intracardiac shunt, and the presence of valvular regurgitation.1-3 In the absence of an intracardiac shunt and valvular regurgitation, one can predict the downslope of the arterial dilution curve, using the calculated values of cardiac output and "central blood volume. " Several investigators have tried to estimate the amount of regurgitation in man by measuring the deviation of the observed downslope from the predicted downslope.4-7 Lange and Hechts have presented evidence suggesting that an estimate of mitral regurgitation may be obtained by comparing the dilution curves recorded simultaneously from the pulmonary artery and the femoral artery. There is evidence from studies on dogs with simulated valvular regurgitation that supports the validity of this technic.9' 10 This is a report of the results of the doubledilution-curve technic in the estimation of mitral regurgitation in 50 patients.