Validity of indicator-dilution determinations of cardiac output in patients with mitral regurgitation.

mHE indicator-dilution method has been widely employed for determination of cardiac output since its introduction by Stewart' and Hamilton and associates.2 The effect of unrecognized recirculation of indicator particles upon the primary indicator time-concentration curve has caused concern as to whether this method may be employed in such conditions as mitral regurgitation3' 4and as to whether the right heart may be employed with validity as an injection site when systemic arterial sampling sites are utilized.5 A previous study from this laboratory has demonstrated that left ventricular cardiac outputs were virtually identical when the pulmonary artery and the left atrium were used as injection sites with sampling from systemic arterial sites.6 The purpose of this report is to examine data as to the effect of mitral regurgitation upon the validity of the indicator-dilution curve for the determination of cardiac output employing right atrial injection and systemic and pulmonary artery sampling.