Impact on Pulmonary Hypertension Hemodynamic Classification Based on the Methodology Used to Measure Pulmonary Artery Wedge Pressure and Cardiac Output.

Rationale: Guidelines recommend using end-expiration pulmonary pressure measurements to determine the hemodynamic subgroups in pulmonary hypertension. Pulmonary artery wedge pressure (PAWP) determinations averaged across the respiratory cycle (PAWPav) instead of PAWP at end-expiration (PAWPee) and cardiac output (CO) measured by Fick (CO_Fick) instead of thermodilution (CO_TD) may affect the hemodynamic classification of pulmonary hypertension. Objectives: To assess the impact on the pulmonary hypertension hemodynamic classification of the use of PAWPee versus PAWPav as well as CO_Fick versus CO_TD. Methods: This was a single-center retrospective study of consecutive patients (n = 151) who underwent right heart catheterization with CO_TD, CO_Fick, PAWPee, and PAWPav. A secondary cohort consisted of consecutive patients (n = 71) who had mean pulmonary artery pressure at end-expiration (mPAPee) and mPAP averaged across the respiratory cycle (mPAPav) measured, as well as PAWPee and PAWPav. Results: The PAWPee and PAWPav were 16.8 ± 6.4 and 15.1 ± 6.8 mm Hg, respectively, with a mean difference of 1.7 ± 2.1 mm Hg. The CO_TD and CO_Fick determinations were 5.0 ± 2.4 and 5.3 ± 2.5 L/min, respectively, with a mean difference of -0.4 ± 1.3 L/min. The hemodynamic group distribution was significantly different when using PAWPee versus PAWPav, when using either CO_TD or CO_Fick (P < 0.001 for both comparisons), and these results were consistent in our secondary cohort. The pulmonary hypertension hemodynamic group distribution was not significantly different between CO_TD and CO_Fick when using either PAWPee or PAWPav. Conclusions: The methodology used to measure PAWP, either at end-expiration or averaged across the respiratory cycle, significantly impacts the hemodynamic classification of pulmonary hypertension.