The Critical Role of Pulmonary Artery Wedge Pressure Saturation In The Standardization of Pulmonary Artery Wedge Pressure Measurement

Introduction Inadequate balloon occlusion while measuring pulmonary artery wedge pressure (PAWP) during right heart catheterization (RHC) may lead to inaccurate measures and clinically relevant misdiagnosis of disease. Following the 6th World Symposium on Pulmonary Hypertension (PH) recommendations, we instituted a standard of care clinical protocol at the Medical University of South Carolina that required obtaining a PAWP saturation (sat) to confirm complete occlusion whenever initially measured PAWP is >15 mmHg. We sought to determine: 1) The difference between initial and lowest reported PAWP 2) The frequency in which this practice leads to a change in PH classification 3) The overall success rate in obtaining a PAWP sat. Methods After IRB approval, investigators not performing the RHC procedure prospectively collected demographic, echocardiographic and hemodynamic data. Subjects undergoing routine post-transplant RHC were excluded. After the initial PAWP measurement (as determined by the RHC operator), a PAWP sat was drawn to confirm occlusion (defined as >90% or within 5% of the systemic arterial oxygen saturation). If the PAWP sat did not confirm occlusion, the balloon was deflated and up to two additional attempts were made to re-measure the PAWP and confirm with a PAWP sat. PAWP were recorded at the same point in the respiratory cycle with each attempt. Repeated measures were compared using Signed Rank Test. Results We enrolled 75 subjects (age 58.3 +/- 13.3 years, 60% men, 59% with LVEF 15 mmHg. Despite apparent confirmation of PAWP position by fluoroscopy and/or typical hemodynamic waveforms, an occlusive PAWP sat was unable to be confirmed in 39 (52%) of subjects during the first attempt. In these subjects, the mean difference between initial and lowest PAWP was -4.1 +/- 7.7 mmHg (p 5 mmHg. Three of the 4 subjects referred for PH with preserved EF were ultimately reclassified as having pre-capillary PH. Eight of the 16 referred for advanced heart failure evaluation were re-classified as combined post- and pre-capillary PH with PVR > 3 WU, which then required vasodilator testing. With additional attempts, a PAWP sat was confirmed in 83% of subjects. There were no observed complications during additional PAWP attempts. Conclusion The practice of requiring a PAWP sat resulted in significantly lower PAWP, higher PVR and clinically relevant disease reclassification. A PAWP sat is a simple and safe technique to verify an elevated PAWP during RHC.