Background <p>Markers for stratifying atrial remodeling severity have not yet been established in atrial fibrillation (AF) with left atrial (LA) enlargement. We evaluated the utility of the atrial to brain natriuretic peptide ratio (ANP/BNP) in stratifying atrial remodeling severity and post-ablation recurrence risk in AF patients with LA enlargement.</p> Methods <p>This study included 220 patients who had undergone catheter ablation for AF. Atrial remodeling was assessed based on the presence of low-voltage areas (&lt; 0.5 mV) on electroanatomic mapping, P-wave duration, and intra-atrial conduction time. The associations of the ANP/BNP with atrial remodeling and recurrence 3–12 months post-ablation were examined in AF patients with LA enlargement, defined as an LA diameter &gt; 45&#xa0;mm on echocardiography.</p> Results <p>Low-voltage areas and AF recurrence were found in 49 (22.2%) and 30 (13.6%) patients, respectively. In multivariate logistic models, the ANP/BNP was related to low-voltage areas (odds ratio 0.457; <i>p</i> = 0.016). Receiver-operating characteristic analysis revealed that ANP/BNP &lt; 0.93 was a predictor of low-voltage areas (area under the curve: 0.718). Patients were classified into three groups: non-LA enlargement (<i>n</i> = 146); LA enlargement with high ANP/BNP (≥ 0.93, <i>n</i> = 27); and LA enlargement with low ANP/BNP (&lt; 0.93, <i>n</i> = 47). Patients with LA enlargement and low ANP/BNP had the highest prevalence of low-voltage areas and intra-atrial conduction disturbances among the three groups. Multivariate Cox models revealed that LA enlargement with low ANP/BNP was an independent predictor for recurrence (hazard ratio, 4.064; <i>p</i> = 0.001).</p> Conclusion <p>The ANP/BNP is useful in stratifying atrial remodeling severity and post-ablation recurrence risk in AF patients with LA enlargement.</p> Graphical Abstract <p></p>