Brief reports

Body composition and prognosis in chronic systolic heart failure: the obesity paradox

Obesity is a major public health challenge worldwide. It is costly, predisposes to many cardiovascular (CV) diseases (CVD), is increasing at an alarming rate, and disproportionately affects people of low-socioeconomic status. It has a myriad of deleterious effects on the body, particularly on the CV system. Obesity is a major risk factor for heart failure (HF) and highly prevalent in this population, particularly in those with HF with preserved ejection fraction (HFpEF), to the extent that an obesity HFpEF phenotype has been proposed in the literature. However, once HF is developed, an obesity paradox exists where those with obesity have better short- and mid-term survival than normal or underweight individuals, despite a greater risk for hospitalizations. It may be argued that excess energy reserve, younger patient population, higher tolerability of HF therapy and better nutritional status may account for at least part of the obesity paradox on survival. Furthermore, body mass index (BMI) may not be an accurate measure of body composition, especially in HF, where there is an excess volume status. BMI also fails to delineate fat-free mass and its components, which is a better predictor of functional capacity and cardiorespiratory fitness (CRF), which particularly is increasingly being recognized as a risk modifier in both healthy individuals and in persons with comorbidities, particularly in HF. Notably, when CRF is accounted for, the obesity paradox disappears, suggesting that improving CRF might represent a therapeutic target with greater importance than changes in body weight in the setting of HF.

In this narrative review, we discuss the current trends in obesity, the causal link between obesity and HF, an update on the obesity paradox, and a description of the major flaws of BMI in this population. We also present an overview of the latest in HF therapy, weight loss, CRF, and the application of these therapeutic approaches in patients with HF and concomitant obesity.

The prognostic value of overweight/obesity in heart failure (HF) may vary according to HF etiologies. We aim to determine whether body mass index has differential impacts on survival among hospitalized HF patients with varying etiologies. Consecutive hospitalized HF patients between December 2006 and December 2017 were included. Multivariable analyses, including Cox proportional hazard models and restricted cubic splines, were used to investigate the impact of body mass index on mortality by HF etiology. Among the 3,836 patients included (mean age 57.1 years, 28.4% women), 1,475 (38.5%) were identified as having ischemic etiology. Of the remaining 2,361 patients with non-ischemic etiologies, dilated cardiomyopathy (DCM) accounted for 45.6% (n = 1,077). The rest of the patients were uniformly classified as having non-ischemic-non-DCM HF. The unadjusted data demonstrated an adiposity-related survival paradox in HF across all etiologies. However, the paradox holds only among non-ischemic-non-DCM HF patients after multivariate adjustment, wherein overweight patients exhibit the lowest mortality compared with their normal-weight counterparts (adjusted hazard ratio [aHR] 0.69, 95% confidence interval [CI] 0.52 to 0.91), with a nadir in mortality risk at 28.18 kg/m². Similar survival benefits of overweight were not demonstrated in ischemic or DCM HF patients (ischemic etiology: aHR 1.07, 95% CI 0.84 to 1.36; DCM etiology: aHR 0.97, 95% CI 0.74 to 1.28). In conclusion, being overweight or obese does not confer better survival in HF patients of ischemic or DCM etiology, and the prognostic benefit of being overweight is maintained only in non-ischemic-non-DCM HF patients. Pathophysiologic interpretations are warranted, and whether patients of certain etiologies would benefit from weight reduction needs to be explored.

Obesity is associated with reduced mortality in some patients hospitalized for heart failure (HF). In this analysis, we determine if this nonlinear relation, referred to as the obesity paradox, extends to secondary outcomes in patients diagnosed with severe obesity. This is a retrospective cohort study using the 2017 and 2018 National Inpatient Sample that includes adults hospitalized for HF. Patients with diagnosis codes specifying severe obesity, nonsevere obesity, or without obesity are compared. The primary outcome is mortality. Secondary outcomes include the length of stay (LOS), total charges, and cardiogenic shock (CS). Multivariate regression is used to adjust for demographics and co-morbidities. A total of 2,439,845 hospitalizations are included. A decreased mortality is found in nonsevere obesity (odds ratio 0.74, 95% confidence interval 0.69 to 0.80, p = 0.000), affirming the obesity paradox. However, this decreased mortality is not found in severe obesity (odds ratio 1.01, 95% confidence interval 0.94 to 1.08, p = 0.766). Severe obesity and nonsevere obesity are also associated with less CS and increased LOS compared with non-obese patients. Severe obesity is associated with increased total charges. In conclusion, a nonlinear, U-shaped relation between obesity and mortality in patients hospitalized for HF is demonstrated, where those not obese and those severely obese experience greater mortality compared with the nonseverely obese. However, for secondary outcomes of CS, LOS, and total charges, the relation is linear and therefore not interpreted as paradoxical. More information is needed using the adiposity-based chronic disease model to characterize complex relations between obesity and mortality.

Obesity is associated with reduced postoperative mortality among patients undergoing cardiovascular surgery. However, body mass index cannot differentiate abdominal fat composition. This study evaluated the relationships between total abdominal, subcutaneous, and visceral fat composition and postoperative mortality in East Asian patients undergoing cardiovascular surgery.

Adult patients who underwent cardiovascular surgery between October 2004 and December 2016 were retrospectively included. Total, subcutaneous, and visceral fat areas were measured from cross-sectional computed tomography images. The relationships between each fat composition and mortality were evaluated.

In all, 3661 patients were analyzed, and overall mortality was 19.9% (729 died) during the 4.6-year median follow-up period. The risks of all-cause and cardiac-cause mortality decreased as subcutaneous fat composition increased (adjusted hazard ratio 0.997; 95% confidence interval, 0.994 to 1.000; and adjusted hazard ratio 0.994; 95% confidence interval, 0.989 to 0.999; P = .02 and P = .01, respectively). No association was detected between the total and visceral fat area and mortality.

Reduced abdominal subcutaneous fat, but not the total or visceral fat composition, was associated with higher all-cause and cardiac-cause mortality after cardiovascular surgery in East Asian patients, consisting mainly of normal weight or overweight patients.