Fluid loading during the hemodynamic evaluation of pulmonary hypertension: a cross-sectional study.

Background: Compensated pulmonary hypertension due to left heart disease (PH-LHD) may be difficult to identify based on resting hemodynamics. Fluid challenge is commonly used to unmask occult PH-LHD. We sought to determine the hemodynamic effect of fluid loading and its association with the clinical pretest probability of PH-LHD. Methods: We included consecutive patients evaluated for PH who underwent right heart catheterization (RHC) with fluid challenge at Cleveland Clinic between April 2013 and January 2019. We obtained hemodynamic measurements at rest and after intravenous rapid fluid challenge (500 mL of normal saline). We calculated the pretest probability of PH-LHD based on the 6th World Symposium on PH proceedings. For statistical analyses we used t-test, analysis of variance (ANOVA), Chi-square, paired t-test, Wilcoxon signed-rank test and linear regression as indicated. Results: We included 174 patients with mean ± standard deviation (SD) age of 63.7±13.0 years and 123 (71%) of female sex. Baseline pulmonary artery wedge pressure (PAWP) was 11±5 mmHg, with a PAWP/cardiac output (CO) ratio of 2.1±1.1 Wood units (WU). The absolute increase in PAWP and PAWP/CO was 6.9±3.6 mmHg and 1.06±0.91 WU, respectively. The change in PAWP was inversely associated with baseline PAWP (P<0.001). The PAWP with fluids was >18 mmHg in 81% of the patients with baseline PAWP 13-15 mmHg. We found no strong associations between the change in PAWP, PAWP/CO or right atrial pressure to pulmonary arterial wedge pressure ratio (RAP/PAWP) and the pretest probability of PH-LHD. Conclusions: The absolute change in PAWP, PAWP/CO, or achieving a PAWP >18 mmHg with rapid fluid loading was not robustly associated with the pretest probability of PH-LHD. Patients with PAWP between 13-15 mmHg commonly had a positive fluid challenge, questioning the utility of this intervention in these patients.