Prognostic Significance of Cardiac Output in Postcapillary Pulmonary Hypertension: Estimated Fick vs. Thermodilution

Background: The prognostic value of cardiac output measured by the estimated Fick method and thermodilution in patients with postcapillary pulmonary hypertension (pc-PH) is unclear. We aimed to compare the correlations and consistency of cardiac output (CO) evaluated by the estimated Fick method and thermodilution, and to assess the prognostic validity of these two cardiac index (CI)-based methods with regard to all-cause mortality in patients with pc-PH. Methods: CO was simultaneously measured by thermodilution and the estimated Fick method using a Swan-Ganz catheter in 257 patients with pc-PH. Oxygen consumption was calculated by Dehmer, LaFarge, and Bergstra formulae. Results: The CO measured by the estimated Fick method combined with the three formulae, and by thermodilution exhibited moderate correlations (r = 0.706, r = 0.688, r = 0.702, respectively; all P < 0.010). The 95% limits of agreement were -2.73 to 1.51, -2.99 to 1.36, and -2.42 to 2.02 L/min, respectively. CI measured by thermodilution was associated with the mortality (HR: 0.75 [95% CI: 0.58-0.98]; P = 0.034). After adjustment, the risk of all-cause mortality was higher in the low CI group assessed by the Dehmer formula (HR: 1.92 [95% CI: 1.10-3.37]; P = 0.022) compared to the high CI group. Conclusions : There were moderate positive correlations and poor agreements between the CO measured by the estimated Fick method and thermodilution in patients with pc-PH. Thermodilution was superior to the estimated Fick method in improving risk stratification for all-cause mortality.