Comparison of left ventricular and pulmonary arterial injection sites in determination of cardiac output by indicator dilution technique.

Cardiac outputs calculated from left ventricular indicator dilution curves were compared to outputs calculated from pulmonary arterial curves in 58 patients with a variety of cardiac abnormalities. Cardiac outputs calculated from left ventricular and pulmonary arterial curves differed by only 0.037 ± 0.052 LI mm. Individual measurements of cardiac output using left ventricular curves had an estimated standard error of 0.41 L/min (9.0 percent of output); individual measurements using pulmonary arterial curves had an estimated standard error of 0.35 L/min (7.7 percent of output). Thus, the two methods gave nearly identical values for cardiac output and were equally reproducible. A significant associadon (P=O.02) was found between mitral regurgitation and dissimilar values for cardiac output determined by the two methods. It is concluded that the site of injection of the indicator does not appreciably influence calculation of cardiac output except in the presence of severe mitral regurgitation.