BACKGROUND: We hypothesised that changes in the left atrial (LA) structure and function would lead to decreased B-type natriuretic peptide (BNP) levels after pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). This study aimed to assess the effect of PVI on LA structure and function, measured using cardiac computed tomography (CT), and its relationship with BNP in patients with AF. METHODS: We retrospectively analysed patients with AF who underwent cardiac CT before and after PVI at our institution between 21 January 2021 and 31 March 2023. LA volume (LAV) and ejection fraction (LAEF) were measured before and after PVI. The relationship between BNP level and the ratio of LAV to body surface area (LAV/BSA) and that between BNP level and LAEF were compared using propensity score matching (PSM) and Pearson's rank correlation coefficient. RESULTS: A total of 228 patients of (mean age, 61.4 ± 10.2 years) were evaluated. The average BNP levels and maximum and minimum LAV/BSA after PVI were significantly lower than those before PVI (p <
0.05). Patients with an increase in BNP level demonstrated a significantly larger mean maximum and minimum LAV/BSA and a lower mean LAEF before and after PSM than those without an increase (p <
0.05). BNP levels were positively correlated with maximum and minimum LAV/BSA, and showed a negative correlation with LAEF (p <
0.001). CONCLUSION: LA structure and function in patients with AF are essential factors affecting BNP secretion, which improves through PVI.