IJCS | Volume 32, Nº5, September/October 2019

529 Mourilhe-Rocha and Salvino Obesity and heart failure Int J Cardiovasc Sci. 2019;32(5):527-535 Review Article Traditionally the major parameter to differentiate the subtypes of HF is LV ejection fraction. That guideline stratifies patients into three groups: HFpEF - those with ejection fraction ≥ 50%; HFrEF - those with ejection fraction < 40%; and mid-range ejection fraction - those with ejection fraction between 40% and 49%, considered to be in a gray zone between the two others. 24 This differentiation is essential for the treatment strategies. To keep the uniformity with most publications analyzed in this review, patients with HFpEF were those with an ejection fraction ≥ 50%, while patients with HFrEF were those with an ejection fraction < 50%. Hemodynamic andmorphological changes associated with obesity Although since the 17 th century the heart of obese individuals has been known to be “enlarged, thick and fibrous”, it was only in 1933 that global myocardial hypertrophy, in the absence of hypertension, was reported for the first time in obesity. 9 It is currently known that, in severe obesity, cardiac output is increased at the expense of increased circulating volume, leading to a state of chronically elevated preload, which favors the increase of ventricular dimensions, of parietal stress and LV mass. 8,12,14,25,26 This set of chronic hemodynamic changes can lead to cardiac structural impairment with cardiac performance loss. The most common change in cardiac morphology related to obesity is LV mass increase, directly related to the development of diastolic dysfunction in obesity. 20 In addition to correlating with obesity, that change correlates with obesity duration. 8 The FraminghamHeart Study has shown that BMI is an independent predictor of LV mass, mainly when BMI exceeds 30 kg/m 2 . 14 The literature is highly controversial regarding the LVH pattern related to obesity. Recent studies, however, have suggested that, in obese individuals, concentric LVH and remodeling are as frequent as, or even more frequent than, eccentric LVH. 10,27 Mild LV systolic dysfunction can be present, but moderate to severe systolic dysfunction is rare and should trigger the search for comorbidities not directly related to obesity. 10,20 The presence of cardiac fibrosis in obese individuals is another important component of ventricular remodeling, increasingmyocardial stiffness and diastolic dysfunction, resulting in clinical HF. Although it is important to recognize that such change can result from multiple conditions frequently associated with obesity, such as AH, dyslipidemia and DM, some studies have shown that fibrous remodeling of the ventricles resulting in significant diastolic dysfunction can occur in the absence of those comorbidities. 8 Factors that contribute to LV systolic dysfunction in obesity include overload conditions, duration of obesity, LV mass increase, and comorbidities, such as coronary artery disease, AH and DM. 20 In addition, the direct toxic effects of the excessive amount of adipose tissue might be related to ventricular remodeling, potentialized by insulin resistance and neurohumoral activation, particularly the renin-angiotensin-aldosterone system and the sympathetic nervous system. 26 Another structural change frequently related to obesity is left atrial enlargement. 14,20 A study has reported left atrial enlargement in 34.0% of obese individuals and in only 6.0% of normal-weight patients. 20 Factors predisposing to left atrial enlargement in obesity include volume overload, LVH and LV diastolic dysfunction. 14,20 Cardiac structural changes can be present even without any clinical sign of heart disease, representing a subclinical manifestation of obesity cardiomyopathy. A cross-sectional study, 25 assessing 30 candidates for bariatric surgery with no history of previous heart disease, has reported enlarged left chambers in 42.9%, diastolic dysfunction in 54.6%, and LVH in 82.1%, with the eccentric pattern of LVH present in half of the cases. The correlations between LVH, obesity duration and blood pressure levels were positive, as were the correlations between BMI and the diastolic dysfunction indicators. Systolic dysfunction was found in only 10.7% of the population studied. 25 The authors have concluded that ventricular mass adjusted for height can be more precise than ventricular mass adjusted for body surface area, and the former might be a more appropriate index to determine ventricular hypertrophy in obese individuals. 14,25 Likewise, Tavares et al., 28 have found higher sensitivity for the diagnosis of LVH in obese individuals when adjusting LV mass for height as compared to body surface area. 28 Obesity cardiomyopathy Patients with advanced obesity and HF with no identifiable cause of LV dysfunction can be diagnosed with obesity cardiomyopathy. 5,6 That condition isdefinedasHF totallyorpredominantly due to obesity. 20 The diagnosis can be difficult because