We evaluated the effects of adjunctive left anterior line (LAL) ablation on LA dyssynchrony and function using real-time three-dimensional echocardiography (3DE) in connection with thromboembolic complications and tachyarrhythmia recurrence in patients with persistent atrial fibrillation (AF). We randomly and prospectively assigned consecutive persistent AF patients to the LAL (n = 52, 65 ± 7 years) and control groups (n = 50, 64 ± 10 years). In the LAL group, extensive encircling pulmonary vein isolation (EEPVI), roof line ablation, and LAL ablation regardless of the extent of the low-voltage area (LVA) were performed. The control group underwent EEPVI and roof line ablation. After ablation, 3DE demonstrated LA dyssynchrony in 23 (46%) and 4 patients (8%, P < 0.001) of the LAL and control groups, respectively. Baseline LA LVAs were relatively small in most patients and there were no significant differences in extent of LVA between control and LAL groups or between patients with and without dyssynchrony. During the follow-up periods (771 ± 121 days), patients with LA dyssynchrony in the LAL group did not show significant differences in symptomatic thromboembolic events (0%) and atrial tachyarrhythmia recurrence (39%) from patients without LA dyssynchrony in the LAL (0% and 30%) and control groups (0% and 32%, respectively). LA ejection fraction and active emptying fraction were lower by 9% on average in the LAL group than in the control group (P < 0.0001). Similarly, in the LAL group, LA ejection fraction, active emptying fraction, and expansion index were significantly lower by approximately 7%, 8%, and 15%, respectively, in LA with dyssynchrony than those in LA without dyssynchrony. In conclusion, LA dyssynchrony and LA hypofunction were induced by LAL ablation in patients with persistent AF and relatively mild LVA. LAL ablation with or without LA dyssynchrony is thought not to affect thromboembolic complications or atrial tachyarrhythmia recurrence.