Estimation of Ventricular Volumes by a Constant Infusion Indicator Dilution Technique
A constant infusion indicator dilution method for estimating ventricular volumes is introduced and its feasibility demonstrated. Using this method, volumes can be calculated by two different approaches, one of which does not assume effective distribution of indicator throughout end diastolic volume (EDV). This offers a means of assessing the effects of nonmixing on the form of the stepwise rise in concentration of the constant infusion curve, which has relevance to the basically related stepwise decline in concentration following sudden injection of indicator. It is suggested that the degree of mixing of diastolic venous return in the previous end systolic volume (ESV) is basic to the distribution of indicator introduced into the ventricle. If mixing is incomplete, the site of origin of stroke volume (SV) from EDV is an important factor in determining the form of an indicator dilution curve and the EDV as calculated from ratios of successive concentrations. The possible range of effects of nonmixing on the form of the constant infusion curve for ventricular volume, as derived from a mathematical model, is outlined. End diastolic volumes, as estimated from ratios of successive concentrations in a series of constant infusion indicator dilution curves obtained experimentally, are tabulated, and as a group do not differ materially from those obtained by the sudden injection method.
- Received January 31, 1964.
- © 1964 American Heart Association, Inc.