Impact of Obesity on Volume Status in Patients With Ambulatory Chronic Heart Failure

Background: Fluid overload is common in heart failure (HF) and obesity; however, the relationship between the extent of intravascular volume expansion and indices such as body mass index (BMI) in obese and non-obese patients with HF has not been defined to address the issue of a HF obesity phenotype. Methods: Total blood volume (TBV) was measured clinically using a radiolabeled albumin indicator-dilution technique in patients with predominately class III ambulatory chronic HF (N=66). Obesity was defined by BMI >= 30 kg/m(2). Results: Markedly increased intravascular volume expansion (defined by TBV expansion >+25% above normal) was highly prevalent in the obese (53%) compared to non-obese patients with HF (29%, P =.04) driven by plasma volume expansion. TBV was correlated with excess body weight and BMI (both P <.01). Also, cardiac index was higher, systemic vascular resistance lower, and left ventricular filling pressures comparable in obese compared with non-obese patients. Conclusions: Quantitative assessment of intravascular volume demonstrates for the first time that severe (not mild or moderate) volume expansion is highly common in obese patients with ambulatory chronic HF. This supports an evolving concept of an obesity-specific HF phenotype. Further study is needed to understand the mechanisms controlling volume regulation and the potential compensatory or detrimental impact on outcomes in obesity and HF.