The Impact of Obesity on Cardiac Function and Morphology in Aortic Stenosis

Abstract

Introduction and objectives: It is known that obesity can directly affect cardiac structure and function, leading to an entity recently described as "obesity cardiomyopathy". Several pathophysiological mechanisms can be involved in this association, such as hemodynamic changes, endocrine effects (through the secretion of adipokines) and paracrine effects related with epicardial fat. In this study, we aimed to evaluate the effect of several adipose tissue parameters on cardiac function and structure in patients with severe aortic stenosis. Methods: We prospectively evaluated a cohort of patients with severe aortic stenosis referred to cardiac surgery (EPICHEART study). Body weight and height were measured to derive body mass index (BMI) and body composition (% fat mass) was determined using bioelectrical impedance analysis. Epicardial fat volume was evaluated using thoracic multidetector CT (SyngoVolume, Siemens Medical Solutions®) and visceral, subcutaneous and total abdominal fat were evaluated by a single-slice abdominal CT at the level of L4-L5. Echocardiography was prospectively performed to analyze cardiac structure (left atrial volume index; left ventricular volumes; left ventricular mass), systolic (Simpson ejection fraction, S' velocity) and diastolic function (E/A ratio; E' velocities; E/E' ratio). In a subset of 145 patients, left atrial function was assessed by speckle-tracking using Velocity Vector Imaging (VVI) software (syngo VVI 2.0, Siemens Medical Solutions USA, Inc) to determine peak LA strain (PALS), peak strain before atrial contraction (PACS), LA passive emptying strain. Results: The final analysis included 272 participants (75,5±8,4 years old, 50% males). Seventy-six patients were obese and 110 were overweight. Overall, patients with higher weight had increased septum and posterior wall thickness and an increased left ventricular mass and volume (ρ=0.274, p <0.001, ρ=0.208, p <0.01, ρ=0,466, p<0,01, ρ=0,231, p=0,048, respectively). We found no significant correlation between adipose tissue parameters, including epicardial fat or visceral abdominal fat, with systolic function (correlation between BMI and Ejection fraction (EF) ρ= 0,040, p=0,59; correlation between EFV and EF ρ=- 0,003, p=0,96; correlation between VAF and EF ρ= 0,043, p=0,58). Regarding the effects of obesity on diastolic function there was no significant association between adipose tissue tissue parameters and diastolic function (correlation between BMI and E/E' ratio ρ= 0,120, p=0,23; correlation between EFV and E/E' ρ=0,173, p=0,10; correlation between VAF and E/E' ratio ρ=-0,054, p=0,61). Although we observed that patients with increased waist circumference and higher epicardial fat volume had an increased LA area (20,65 to 23,12 cm2, p<0,01; 20,88 to 23,78 cm2, p=0,039, respectively), adipose tissue parameters did not influence LA function (reservoir, conduit or pump function) assessed by speckle-tracking Conclusions: Contrary to what has been observed in other populations, in patients with severe aortic stenosis we did not observe a significant effect of adipose tissue parameters, including epicardial fat, in cardiac structure or systolic/diastolic function. LA function assessed by speckle tracking analysis also did not correlate with adipose tissue. Therefore, it is likely that, in patients with severe aortic stenosis, the impact of increased post-load in cardiac structure and function off-sets the effect of adipose tissue in heart remodeling.