Discrepancy between thermodilution and radionuclide right ventricular ejection fraction measurements: the importance of tricuspid regurgitation.

Measurement of right ventricular ejection fraction (RVEF) by the thermodilution technique has become routinely available at the bedside of the critically ill. We describe 2 patients with tricuspid regurgitation in whom RVEF values were considerably lower by thermodilution than by radionuclide techniques. Discrepancies could be due to the regurgitation of the thermodilution signal and possibly to the different nature of the two measurements (forward stroke volume with the thermodilution technique and total stroke volume with the radionuclide technique). We suggest that lower RVEF measurement by the thermodilution technique could be related to unrecognized tricuspid regurgitation. Measurement of an unexpectedly low RVEF by the thermodilution technique should suggest the presence of tricuspid regurgitation.