Heart failure
Influence of Etiology of Heart Failure on the Obesity Paradox

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Several investigations have demonstrated that higher body weight, as assessed by the body mass index, is associated with improved prognosis in patients with heart failure (HF). The purpose of the present investigation was to assess the influence of HF etiology on the prognostic ability of the body mass index in a cohort undergoing cardiopulmonary exercise testing. A total of 1,160 subjects were included in the analysis. All subjects underwent cardiopulmonary exercise testing, at which the minute ventilation/carbon dioxide production slope and peak oxygen consumption were determined. In the overall group, 193 cardiac deaths occurred during a mean follow-up of 30.7 ± 25.6 months (annual event rate 6.0%). The subjects classified as obese consistently had improved survival compared to those classified as normal weight (overall survival rate 88.0% vs ≤81.1%, p <0.001). Differences in survival according to HF etiology were observed for those classified as overweight. In the ischemic subgroup, the survival characteristics for the overweight subjects (75.5%) were similar those for subjects classified as normal weight (81.1%). The converse was true for the nonischemic subgroup, for whom the survival trends for the obese (86.4%) and overweight subjects (88.4%) were similar. The minute ventilation/carbon dioxide production slope was the strongest prognostic marker (chi-square ≥43.4, p <0.001) for both etiologies, and the body mass index added prognostic value (residual chi-square ≥4.7, p <0.05). In conclusion, these results further support the notion that obesity confers improved prognosis in patients with HF, irrespective of the HF etiology. Moreover, the body mass index appears to add predictive value during the cardiopulmonary exercise testing assessment. However, survival appears to differ according to HF etiology in subjects classified as overweight.

Section snippets

Methods

The present study was a multicenter analysis of patients with HF from the exercise testing laboratories at San Paolo Hospital (Milan, Italy), Wake Forrest University Baptist Medical Center (Winston-Salem, North Carolina), LeBauer Cardiovascular Research Foundation (Greensboro, North Carolina), Veterans Affairs Palo Alto Health Care System (Palo Alto, California), and Virginia Commonwealth University (Richmond, Virginia). A total of 1,160 patients diagnosed with chronic HF were included. The

Results

The baseline and CPX characteristics for the study group subdivided according to HF etiology and BMI are listed in Table 1. The ischemic HF subgroup was significantly older and included more men compared to the nonischemic HF group, irrespective of BMI classification. Within both HF etiology subgroups, patients classified as obese were significantly younger. A significantly lower percentage of normal weight subjects were prescribed a β-blocking agent at testing, irrespective of the HF etiology.

Discussion

The results of the present investigation are consistent with those of previous trials,2, 7 demonstrating that a greater BMI, although it increases the risk of the development of HF,8 improves survival once a patient has been diagnosed with HF. Previous investigations have used various low-end thresholds to define normal weight, including ≥18.5 kg/m2 and ≥22.0 kg/m2.9, 10 Our findings are consistent with those of previous investigations by demonstrating a poor prognosis for normal weight

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    This study was supported in part by Grants R37AG18915 and P60AG10484 from the National Institutes of Health, Bethesda, Maryland.

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