Obesity or underweight can complicate and aggravate symptoms and progression of right heart failure in patients with pulmonary arterial hypertension (PAH). This study investigate the influence of different body mass index (BMI) categories on right heart function and outcome in PAH patients.

Methods: In this cross-sectional study with survival follow-up (mean follow-up 3.1 ± 2.6 years), clinical measures such as WHO-functional class (FC) and invasively measured hemodynamic parameters at initial diagnosis of PAH were compared between different BMI groups.

Results: Out of 2055 datasets, 755 patients with PAH were eligible for the study (65 ± 15 years, 44.9% idiopathic PAH, 64.8% WHO functional class III or IV). Out of them 15 patients were underweight (BMI < 18 g/m2), 248 patients had a normal weight (BMI 18.5-25 g/m2), 256 were overweight (BMI > 25-30 g/m2) and 236 patients were classified as obese (BMI > 30 g/m2). Cardiac output (CO) significantly differed between BMI groups (Figure 1). A significant but weak correlation could be shown for CO and BMI (p<0.0001, R=0.268). Men showed a higher CO than women (p=0.004), with less distinct differences in groups with higher BMI. There was no association between hyperdynamic status and elevated BMI. In multivariable age-adjusted survival analysis, BMI-status, sex and right ventricular function, but not CO and cardiac index, were identified as independent predictors of survival.

Conclusion: In this study cohort, a weak association could be found between BMI-status and CO. Hyperdynamic CO was more frequent in underweight patients. BMI-status, sex and RV function were superior to predict survival.