ABSTRACT
BACKGROUND: Obesity confers higher risks of cardiac arrhythmias. The extent to which weight loss reverses subclinical proarrhythmic adaptations in arrhythmia-free obese individuals is unknown. OBJECTIVE: To study structural, electrophysiological and autonomic remodelling in arrhythmia-free obese patients, and their reversibility with bariatric surgery using electrocardiographic imaging (ECGi). METHODS: Sixteen arrhythmia-free obese patients (43+12years, 13 female, BMI 46.7+5.5kg/m2) had ECGi pre-bariatric surgery (PreSurg), of which twelve had ECGi post-surgery (PostSurg, 36.8+6.5kg/m2). Sixteen age- and sex-matched lean healthy individuals (42+11 years, BMI 22.8+2.6kg/m2) acted as controls and had ECGi once. RESULTS: Obesity was associated with structural (increased epicardial fat volumes and left ventricular mass), autonomic (blunted heart rate variability) and electrophysiological (slower atrial conduction and steeper ventricular repolarisation gradients) remodelling. Following bariatric surgery, there was partial structural reverse remodelling, with a reduction in epicardial fat volumes (68.7cm3 vs 64.5cm3, p=0.0010) and left ventricular mass (33g/m2.7 vs 25g/m2.7, p<0.0005). There was also partial electrophysiological reverse remodelling with a reduction in mean spatial ventricular repolarisation gradients (26mm/ms vs 19mm/ms, p=0.0009), although atrial activation remained prolonged. Heart rate variability, quantified by standard deviation of successive differences of RR intervals, was also partially improved following bariatric surgery (18.7ms vs 25.9ms, p=0.017). Computational modelling showed PreSurg obese hearts had a greater window of vulnerability to unidirectional block and had earlier spiral-wave break-up with more complex re-entry patterns than PostSurg counterparts. CONCLUSION: Obesity is associated with adverse electrophysiological, structural and autonomic remodelling that is partially reversed after bariatric surgery. These data have important implications for bariatric surgery weight thresholds and weight loss strategies.
