Routine measurements of left and right ventricular output by gated blood pool emission tomography in comparison with thermodilution measurements: a preliminary study

The aim of this preliminary study was to evaluate the accuracy of left and right ventricular output computed from a semi-automatic processing of tomog raphic radionuclide ventriculography data (TRVG) in comparison with the con ventional thermodilution method. Twenty patients with various heart disease s were prospectively included in the study. Thermodilution and TRVG acquisi tions were carried out on the same day for all patients. Analysis of gated blood pool slices was performed using a watershed-based segmentation algori thm. Right and left ventricular output measured by TRVG correlated well wit h the measurements obtained with thermodilution (r=0.94 and 0.91 with SEE=0 .38 and 0.46 l/min, respectively, P<0.001). The limits of agree ment for TR VG and thermodilution measurements were -0.78-1.20 l/min for the left ventr icle and -0.34-1.16 l/min for the right ventricle. No significant differenc e was found between the results of TRVG and thermodilution with respect to left ventricular output (P=0.09). A small but significant difference was fo und between right ventricular output measured by TRVG and both left ventric ular output measured by TRVG (mean difference=0.17 l/min, P=0.04) and therm odilution-derived cardiac output (mean difference=0.41 l/min, P=0.0001). It is concluded that the watershed-based semi-automatic segmentation of TRVG slices provides non-invasive measurements of right and left ventricular out put and stroke volumes at equilibrium, in routine clinical settings. Furthe r studies are necessary to check whether the accuracy of these measurements is good enough to permit correct assessment of intracardiac shunts.