In vitro validation of a right ventricular thermodilution ejection fraction system

Right ventricular ejection fraction (RVEF) is used clinically as an index of right ventricular (RV) pump function. Clinical measurements of RVEF are complicated by the need for complex imaging equipment to compute RV volumes. Recently, the use of thermodilution (TD) methods have been suggested as a simplified means to measure RVEF (RVEF_TD) in patients using rapid response thermistors. Validation, however, by comparison of RVEF_TD and other methodsin vivo, is difficult. Accordingly, thermodilution derived EF measurements (EF_TD) were compared to known values using anin vitro system, with known ejection fractions (EF) set from 17–78% and stroke rates varying independently from 50–100 strokes/min. EF_TD was computed by fitting the downslope of the TD curve to a monoexponential function and computing the time constant of thermal decay. A significant correlation existed between EF_TD and actual EF over the entire study (r=0.96, p<0.001). Bias analysis showed that the points were within a 95% confidence interval of ±12%. Multivariate analysis showed that stroke rate did not significantly affect TD measurements (r=0.03, p>0.7). This study demonstrates that TD accurately predicts EF using anin vitro system and appears to be independent of stroke rate. Thus, TD methods may provide an accurate, simple and reliable means to serially measure RVEF in the clinical setting. This work was supported in part by a Grant-in-Aid from the American Heart Association, and the Bioengineering Alliance of South Carolina.