Timing of left atrial functional recovery and volumetric remodeling after radiofrequency catheter ablation for paroxysmal atrial fibrillation

Background The temporal relationship between left atrial (LA) functional recovery and structural remodeling after radiofrequency catheter ablation for paroxysmal atrial fibrillation remains incompletely characterized. Objective To characterize the temporal evolution of LA volume and function after ablation using serial cardiac magnetic resonance imaging (CMR). Methods Patients with paroxysmal atrial fibrillation underwent CMR before ablation (T0), immediately after (T1), and at three months (T3). Each patient also underwent one intermediate follow-up scan at either 24 hours (T2a), one week (T2b), or one month (T2c) after ablation. LA volume, total, active, and passive emptying fractions, and reservoir, conduit, and booster pump strain were quantified using CMR feature tracking on steady state-free precession cine 2-chamber and 4-chamber acquisitions. Results 26 patients (19% female, age 62.5 ± 6.6) were enrolled. LA function decreased significantly immediately after ablation, consistent with acute atrial stunning. This decrease was most pronounced in LA active emptying fraction (from 35.9 ± 16.7 at T0 to 11.6 ± 13.7 at T1, p < 0.001) and LA booster pump strain (from 13.3 ± 8.0 at T0 to 3.9 ± 2.0 at T1, p < 0.001). Functional parameters recovered between one week and one month after ablation. LA maximum volume demonstrated a delayed but progressive reduction (from 88.3 ± 26.5 ml at T0 to 79.5 ± 22.8 ml at T3, p=0.026), consistent with reverse atrial remodeling. Conclusion Following radiofrequency catheter ablation for paroxysmal atrial fibrillation, LA stunning and functional recovery precede structural volumetric remodeling, suggesting distinct temporal mechanisms.