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

A total of 532 groups of indicator-dilution determinations of cardiac index were performed in four groups of patients, many with mitral regurgitation. The indicator, indocyanine green, was injected into the right atrium and sampled from both the pulmonary and systemic arterial trees. The potential problem imposed by early recirculation of indicator particles was present in the latter but not the former dilution curves. The absence of physiologically significant differences between the two sampling sites demonstrates that even severe mitral regurgitation does not vitiate indicator-dilution determination of cardiac output after right heart injection and systemic arterial sampling if the downstroke of the primary dilution curve permits a straight line semilogarithmic extrapolation.