Validation of right and left ventricular conductance and echocardiography for cardiac function studies

Background. Continuous estimation of left ventricular volume from instantaneous conductance has compared favorably with ''gold standards,'' is less labor intensive, and provides real-time data. Little information exists, however, correlating right ventricular conductance with such gold standards or examining the effects of an electrical field generated in the opposite ventricle. Methods. In open-chested sheep, right and left ventricular conductance, two-dimensional echocardiography, and thermodilution cardiac outputs were measured at steady-state conditions. After these measurements, postmortem pressure-volume relations, ventricular mass, and ventricular casting were performed. Results. The corrected end-diastolic volume measured by conductance correlated well with volumes measured by echocardiography (r = 0.89), postmortem pressure-volume relations (r = 0.84), and casts (r = 0.85). Left ventricular end-diastolic volume measured by conductance did not differ significantly from other standards by analysis of variance. The presence of an electrical field in the opposite ventricle did not affect measured conductance in the studied ventricle. Conclusions. Conductance is useful for the measurement of right and left ventricular end-diastolic volumes in the beating heart and is not affected by the presence of an electrical field in the opposite ventricle. Hence, conductance is a useful tool in studies involving interventricular dependence and function.