Cardiac Output During Exercise: Thermodilution Versus Direct Fick

Background Accurate cardiac output (CO) measurements during exercise are essential for the diagnosis of exercise pulmonary hypertension (PH), exercise precapillary PH, and exercise postcapillary PH. The purpose of this study is to compare performance of thermodilution CO to gold‐standard direct Fick CO (dfCO) at rest and exercise. Methods A single‐center prospective cohort study of patients undergoing invasive cardiopulmonary exercise test over a 3‐year period. For the primary outcome, we predicted CO at each stage of exercise and recovery using generalized additive modeling. In secondary analysis, we assessed mean differences in CO across exercise stages and Bland–Altman analysis at rest and peak exercise. Finally, we assessed the impact in classification of exercise PH, exercise precapillary PH, and exercise postcapillary PH between the 2 CO methods. Results A total of 302 patients were included. In the primary analysis, the generalized additive model smooth term was significantly different between thermodilution and dfCO ( P