Effect of Weight Loss on Early Left Atrial Myopathy in People With Obesity But No Established Cardiovascular Disease

Abstract

Background Obesity is associated with left atrial (LA) remodeling (ie, dilatation and dysfunction) which is an independent determinant of future cardiovascular events. We aimed to assess whether LA remodeling is present in obesity even in individuals without established cardiovascular disease and whether it can be improved by intentional weight loss. Methods and Results Forty-five individuals with severe obesity without established cardiovascular disease (age, 45±11 years; body mass index; 39.1±6.7 kg/m²; excess body weight, 51±18 kg) underwent cardiac magnetic resonance for quantification of LA and left ventricular size and function before and at a median of 373 days following either a low glycemic index diet (n=28) or bariatric surgery (n=17). Results were compared with those obtained in 27 normal-weight controls with similar age and sex. At baseline, individuals with obesity displayed reduced LA reservoir function (a marker of atrial distensibility), and a higher mass and LA maximum volume (all P<0.05 controls) but normal LA emptying fraction. On average, weight loss led to a significant reduction of LA maximum volume and left ventricular mass (both P<0.01); however, significant improvement of the LA reservoir function was only observed in those at the upper tertile of weight loss (≥47% excess body weight loss). Following weight loss, we found an average residual increase in left ventricular mass compared with controls but no residual significant differences in LA maximum volume and strain function (all P>0.05). Conclusions Obesity is linked to subtle LA myopathy in the absence of overt cardiovascular disease. Only larger volumes of weight loss can completely reverse the LA myopathic phenotype.

Keywords: left atrial myopathy; obesity; reservoir strain; weight loss.

Figure 1. Relationship between obesity and cardiac parameters.

Baseline (in red) and follow‐up (in blue) measurements of left ventricular (A through C) and atrial (D through G) parameters assessed by cardiac magnetic resonance are reported in individuals with obesity. EF indicates ejection fraction or emptying fraction; FU, follow‐up; LA, left atrium; LVlong, left ventricle longitudinal; and LV, left ventricle. These measurements were compared with lean controls (in green), and significant differences are reported as * or ** corresponding to P<0.05 or P<0.01, respectively.

Figure 2. Effects of levels of intentional weight loss on cardiac parameters.

Levels of weight loss were calculated as tertiles of excess body weight percentage loss with a color‐coded legend also reported. Changes in left ventricular mass (A), left atrial maximum volume (B), and left atrial reservoir strain (C) stratified for different levels of weight loss (ie, tertiles of excess body weight percentage loss) are also shown as well as the correlation between excess body weight percentage loss and cardiac parameters. Comparisons for changes in cardiac parameters between tertiles of weight loss are reported in Table S1. Left ventricular mass changes linearly with changes in excess body weight percentage loss (A, $\mathrm{y}=-5.17-0.3*\mathrm{x}$) while left atrial reservoir strain changes quadratically (C, $\mathrm{y}=-0.074*\mathrm{x}+0.003*\mathrm{x}*\mathrm{x}$). The overall population of 45 participants is stratified per tertile of weight loss with 15 individuals within each tertile. LA indicates left atrium; and LV, left ventricle.

Figure 3. Correlation between loss of visceral fat and cardiac parameters.

Correlation between loss of visceral fat and left ventricular mass, left atrial volume, and left atrial reservoir strain. There is also a color‐coded stratification according to tertiles of excess body weight percentage loss. LA indicates left atrium; and LV, left ventricle.