Changes in adipose tissue depots and cardiac geometry following bariatric surgery
Authors: Henry J A , Abdesselam I , Sorimachi H , Rayner J J , Deal O , Byrne J , Neubauer S , Borlaug B A , Rider O J 
Published: October 2022

Abstract

Introduction
Cardiac geometry is affected by body composition, with total body adipose volume being related to left ventricular (LV) dilatation (due to increased intravascular volume and cardiac output), and visceral adipose tissue (VAT) to smaller LV cavity size and concentric remodelling (because of insulin resistance) [1]. As such we hypothesised that changes in VAT and total body weight during weight loss would have a differential impact on cardiac geometry. Alongside this, we hypothesised that, as the pericardium is a fixed volume, changes in epicardial adipose tissue (EAT), may have an additional mechanical effect by reducing pericardial restraint.

Purpose
We sought to investigate long term changes in VAT, total weight and EAT following bariatric surgery and relate them to changes in cardiac geometry.

Methods
Forty patients underwent cardiac magnetic resonance (CMR) imaging before and after bariatric surgery, including 21 who underwent short-term (median 209 days), 28 medium-term (median 428 days) and 12 long-term (median 1030 days) imaging follow up. Cardiac volumes (left atrial (LA), LV end-diastolic volume (LVEDV) and stroke volume (LVSV)) were assessed using cardiac MRI. VAT was assessed at L5 using a T1 weighted, water suppressed sequence. EAT volumes were calculated by manual contouring in end-ventricular systole on short axis slices from the mitral valve to the apex. Percentage changes in volumes were calculated between scans for each individual.

Results
Patients on average lost 32kg within the first 428 days following bariatric surgery (54% excess weight loss, p&lt;0.0001), with no significant change in weight at the longer-term time point (Figure 1A). Most VAT loss occurred in the first 209 days (−42%, p&lt;0.0001) with no subsequent change observed at the final two timepoints (Figure 1B). Similarly, EAT loss occurred in the first 209 days (−13%, mean 10ml, p&lt;0.0001) with non-significant changes thereafter (Figure 1C).
There was a significant decrease in both LA (13%, mean 12ml, p&lt;0.0001) and LVEDV (4%, mean 8ml, p=0.0249) at 209 days post-surgery. Both LA volume and LVEDV had returned to baseline by the longest term time point of 1030 days (Figure 2). LVSV followed a similar pattern being reduced at 209 days (by 10%, mean 9ml, p=0.0019), then returning to levels similar to those pre-weight loss at 1030 days (p=0.44) (Figure 2C).

Conclusions
Cardiac volumes show a biphasic response to weight loss, initially becoming smaller and then returning to baseline by 1030 days. We hypothesise that the early drop in LA and LV cavity size is a response to reduced volume from body mass reduction. In contrast, we propose that the increase in LA and LVEDV that follows results from the longer-term effects of reducing VAT, and increased space within the pericardium resulting from EAT loss allowing expansion to occur.

Funding Acknowledgement
Type of funding sources: Foundation. Main funding source(s): We acknowledge support from the British Heart Foundation Oxford Center of Research Excellence