The Impact of Obesity on Pressure-Volume Relationship in Ambulatory Heart Failure

Assessment of volume status is essential in heart failure (HF) management, yet the relationship between cardiac filling pressures and true intravascular volume remains unclear, especially in patients with obesity. We analyzed 262 ambulatory HF patients who underwent blood volume analysis (BVA) and same-day right heart catheterization. Patients were stratified by BMI into non-obese (n = 104), obese (n = 121), and morbidly obese (n = 37). Cardiac filling pressures showed modest correlations with directly measured total blood volume (TBV); RAP correlated with TBV %deviation (r = 0.36-0.58), while PCWP correlations were weaker (r = 0.19-0.36) and non-significant in morbidly obese patients. Concordance between pressure and volume was highest in non-obese patients (RAP/TBV 79.8%, PCWP/TBV 69.2%) and lower in obese (66.1%, 55.4%) and morbidly obese individuals (64.9%, 67.6%). Approximately one-third or more of obese patients exhibited discordant pressure-volume profiles. These findings suggest that in obesity, cardiac filling pressures may not reliably reflect volume status.