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Updated: May 22, 2026

Determination of Cardiac Output in a Porcine Model for Ex Vivo Pulmonary Perfusion
Published on: June 28, 2024
Utility of Direct Fick Cardiac Output in Patients with Left Ventricular Assist Devices
Joshua A Rushakoff1, Ashley G Swavely2, Ryan M Edwards3
1Division of Cardiology, Duke University Medical Center, Durham, North Carolina; Duke Clinical Research Institute, Durham, North Carolina.
Background:
The accuracy of the methods of cardiac index (CI) calculation and their relationship with clinical outcomes in patients with left ventricular assist devices (LVADs) is unclear.
Objectives:
We sought to evaluate direct and indirect methods for CI calculation in patients with LVADs and assess the association of these estimations with clinical outcomes.
Methods:
We reviewed all adult patients who underwent right heart catheterization (RHC) at a Duke University Hospital between March 1, 2021 and April 30, 2025 and identified 140 patients (151 instances of RHC) with LVADs and simultaneous resting oxygen consumption (VO2) measurement. VO2 was measured for calculation of direct Fick (dFick) CI and estimated VO2 was used to calculate indirect Fick (iFick). Coefficient of determination and Bland-Altman analysis was used to compare the iFick and dFick methods. Univariate and multivariate logistic regressions were performed to assess the relationship of the CI method and composite outcome of death/heart transplant/heart failure hospitalization.
Results:
Correlation between dFick CI and iFick CI estimation was poor (R2 = 0.37, 0.36, 0.25, 0.42 for Dehmer, LaFarge, Bergstra, and body mass index-adjusted Dehmer, respectively) without directional bias. Greater than 25% difference between the indirect and direct Fick was common. In a multivariate model, only direct CI was associated with decreased odds of the composite outcome (odds ratio, 0.440; P = .022).
Conclusions:
There is poor correlation between indirect methods of CI calculation compared with dFick CI in patients with LVADs. In our cohort, a lower dFick significantly predicted a composite outcome of death, heart failure, and need for heart transplantation.
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