BackgroundThe diameter of the left atrium (LA) is a major index of prediction for LA fibrosis and ablation outcome in atrial fibrillation (AF). However, an unenlarged LA may not be associated with good results in some cases of AF ablation.ObjectiveExploring the characteristics and ablation prognosis of the patients with fibrotic but unenlarged LAMethodsPatients with persistent fibrillation who underwent catheter ablation in our center were analyzed in this retrospective study. Comprehensive low voltage mapped in LA is considered a fibrotic LA. The patients with fibrotic but unenlarged LA, normal LA, and fibrotic tissue with enlarged LA were included in Groups A, B, and C, respectively. We compared clinical features, electrophysiological findings, immediate ablation results, and follow-up outcomes in three groups.ResultsWe enrolled 9 patients in Group A, 38 in Group B, and 12 in Group C. There were greater proportions of women, low ventricular rates, and high CHA2DS2-VASC scores in the patients with fibrotic LA (Groups A and C). At the end of procedure, all of the patients saw restored sinus rhythm, and the rate of sinus rhythm was lower in Groups A and C than in Group B. Atrial-ventricular block and very-early-stage recurrence were more common in Group A. Sinus rhythm maintenance and LA reversion were rarer in Group A than in Group B or C.ConclusionsA fibrotic but unenlarged LA was more likely to be seen in female with high CHADS2VA2S score. It indicated a poor prognosis for AF ablation.