The impact of obesity on the left atrium and arrhythmia recurrence in patients with atrial fibrillation undergoing ablation

Abstract Background Obesity and atrial fibrillation (AF) are strongly linked and the prevalence of both conditions is steadily increasing worldwide. The prevalence of obesity is higher among patients with AF than in the healthy population. Both conditions are associated with a significant left atrial (LA) pathology. The aim of our study was to evaluate the differences in LA size and function in patients with AF, depending on the presence of obesity. The incidence of AF recurrence in both groups was also assessed. Methods All patients with AF undergoing first-time ablation for AF between March 2019 – January 2024 were retrospectively analysed. They all had a comprehensive echocardiogram on the day of ablation. Patients were classified into 2 groups, according to the presence of obesity defined as BMI≥30kg/m2 (obese and non-obese group). An analysis of the whole group and a sub-analysis of subgroup with sinus rhythm during echocardiography was performed (to expand LA function assessment and exclude the influence of heart rhythm). Results A total of 735 patients were included (median age 66; 39.1% women) of whom 308 (45.8% ) were obese. The comparative analysis of obese and non-obese patients showed higher LA size values (LAarea, LAV, LAVI assessed by indexed to height2 (but not that indexed to BSA), p<0.001) (Fig.1), more impaired echocardiographic parameters related to LA pressure: higher LA stiffness index (p=0.004), E wave velocity (p=0.002) and E/e' average ratio (p<0.001), as well as higher LA mean pressure measured directly during ablation (p<0.0001) in the obese ones (Table 1). However, there were no differences between obese and non-obese groups in terms of parameters directly assessing LA function (LA emptying fraction, LA reservoir strain, LA appendage velocity). The results obtained on the whole group were confirmed by the sub-analysis of the sinus rhythm group (n=374), where no differences were found between the obese vs. non-obese group regarding additional LA parameters such as LA conduit strain, LA contraction strain, LA contraction systolic index, A wave, a’medial and lateral. The AF recurrence rate assessed after 1 year did not differ between the obese and non-obese group (data available for 63.2% (425) patients; p=0.39) regardless of the initial type of rhythm (AF vs. sinus rhythm). Conclusions In patients with AF undergoing their first ever ablation obesity was related with enlarged LA dimensions and higher LA pressure, as assessed both invasively and non-invasively. It should be emphasized that the results of our analysis suggest indexing LA size in obese patients to height2 rather than to BSA, as this measurement correlates better with other parameters of LA size. The LA function, evaluated using specific echocardiographic parameters, and recurrence rate of AF did not differ between obese and non-obese patients.