Abstract Body (Do not enter title and authors here): Background: Recovery of left atrial (LA) function following catheter ablation for atrial fibrillation (AF) has been associated with favorable outcomes, such as reduced risk of recurrence and improved prognosis. However, clinical determinants of post-ablation improvement in LA function remain poorly understood. Recent studies have suggested an emerging association between obesity and impaired LA function.

Hypothesis: We hypothesized that long-term changes in body weight (BW) following AF ablation are associated with the extent of atrial reverse remodeling.

Objective: This study aimed to evaluate the association between longitudinal patterns of post-ablation BW change and changes in LA reservoir strain (LASr) assessed by transthoracic echocardiography (TTE).

Methods: This prospective, single-center observational study enrolled patients who underwent catheter ablation for AF between August 2022 and June 2024. BW and TTE were assessed at three timepoints: baseline, within 2 days post-ablation, and at 1-year follow-up (Figure 1). Patients were classified using latent class growth modeling (LCGM) based on their longitudinal BW trajectories. To evaluate the time course of LASr, a mixed-effects model for repeated measures (MMRM) was constructed with class, timepoint, and their interaction as fixed effects, and individual patients included as a random effect. The model was adjusted for age, sex, baseline body mass index (BMI), number of previous ablations, left ventricular ejection fraction, and baseline LASr value.

Results: A total of 147 patients were analyzed (median age 70 years, 62% male, median BMI 25 kg/m², 66% with paroxysmal AF). Based on BW trajectories, LCGM identified two distinct classes: Class 1 (n = 119) with minimal BW change and Class 2 (n = 24) with marked BW reduction (Figure 2). In the MMRM analysis, baseline LASr was strongly associated with subsequent changes in LASr (p < 0.001), while class alone was not significant (Class 1 vs. 2: p = 0.13). However, a significant interaction between class and timepoint was observed (p = 0.036), indicating greater improvement in LASr over time in Class 2 (Figure 3).

Conclusions: Post-ablation BW change patterns may be associated with the recovery of LA function. These findings highlight the need for further investigation into the relationship between atrial reverse remodeling and weight dynamics following AF ablation.