The applicability of the indicator dilution method to the measurement of left ventricular volume has been studied. When compared with angiocardiographic measurements, the dilution technique overestimates volume by an average of 52 and 91% in end diastole and end systole respectively. Studies which demonstrated more rapid indicator washout from the outflow than from the apical portion of human and canine left ventricles suggest that faulty intraventricular indicator dispersion is the major cause of the volume over-estimates yielded by the dilution method. Procedures designed to alter ventricular size by altering venous return produced parallel changes in ventricular circumference and in ventricular indicator washout volume. The indicator dilution method does not provide a measure of left ventricular volume, but may, in carefully designed studies, yield an index of changes in ventricular size.

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