The atrial defibrillation threshold (ADFT) for internal cardioversion is theoretically related to the critical mass for sustaining atrial fibrillation (AF).

This study aimed to investigate the association of ADFT for internal cardioversion with the outcome of catheter ablation for non-paroxysmal AF (non-PAF).

We included 368 consecutive patients who underwent first-time catheter ablation for non-PAF. Based on the degree of ADFT recorded by the internal cardioversion before pulmonary vein isolation, we divided the patients into low ADFT (<20 J) and high ADFT (≥20 J) groups and analysed the association between ADFT and atrial tachyarrhythmia recurrence.

There were 234 and 134 patients in the low and high ADFT groups, respectively. Of these, 39 patients (16.7%) and 41 (30.6%) patients, respectively, had atrial tachyarrhythmia recurrence during the 2.6±1.0 year follow-up. The high ADFT group showed a significantly higher atrial tachyarrhythmia recurrence than the low ADFT group (p=0.002). This finding was also noted in patients with long-standing persistent AF (p=0.032) but not in patients with persistent AF (p=0.159). The significant predictors of arrhythmia recurrence on multivariate analysis were high ADFT (p=0.004) and long-standing persistent AF (p=0.011). In multivariate analysis within the long-standing persistent AF group, only ADFT remained a significant risk factor for AF recurrence (p=0.035).

The high ADFT of internal cardioversion was found to be a risk factor for post-catheter ablation recurrence in patients with long-standing persistent AF but not in those with persistent AF.