The association between obesity, mortality and filling pressures in pulmonary hypertension patients; the "obesity paradox".

BACKGROUND: The term "obesity paradox", refers to lower mortality rates in obese patients, and is evident in various chronic cardiovascular disorders. There is however, only scarce data regarding the clinical implication of obesity and pulmonary hypertension (PH). Therefore, in the current study, we evaluated the possible prognostic implications of obesity in PH patients.
METHODS: We assessed 105 consecutive PH patients for clinical and hemodynamic parameters, focusing on the possible association between Body Mass Index (BMI) and mortality. Follow-up period was 19 ± 13 months.
RESULTS: Sixty-one patients (58%) had pre-capillary PH and 39 patients (37%) out-of-proportion post-capillary PH. During follow-up period, 30 patients (29%) died. Death was associated with reduced functional-class, inverse-relation with BMI, higher pulmonary artery and right atrial pressures, pulmonary vascular resistance and signs of right ventricular failure. In multivariate analysis, obesity (BMI ≥ 30 kg/m²), was the variable most significantly correlated with improved survival [H.R 0.2, 95% C.I 0.1-0.6; p = 0.004], even after adjustment for baseline characteristics. Obese and very-obese (BMI ≥ 35 kg/m²) patients had significantly less mortality rates during follow-up (12% and 8%, respectively) than non-obese patients (41%), p = 0.01. The tendency of survival benefit for the obese vs. non-obese patients was maintained both in the pre-capillary (10% vs. 46% mortality, p = 0.008) and disproportional post-capillary PH patients (11% vs. 40% mortality, p = 0.04).
CONCLUSIONS: Obesity was significantly associated with lower mortality in both pre-capillary and disproportional post-capillary PH patients. It seems that in PH, similarly to other chronic clinical cardiovascular disease states, there may be a protective effect of obesity, compatible with the "obesity paradox".