Severe abnormal conduction zone in the left atrium causes atrial tachycardia occurrence following catheter ablation for atrial fibrillation

Background Predictors of atrial fibrillation (AF) recurrence after AF ablation have been well studied; however, predictors of atrial tachycardia (AT) occurrence remain unclear. Abnormal left atrial conduction has gained attention as a possible substrate for AT. Purpose To compare factors linked to AT occurrence and AF recurrence following catheter ablation for AF. Methods We studied 202 patients (103 non-paroxysmal AF, 133 males, and 68±10 years) who underwent their first catheter ablation (pulmonary isolation only) for AF. High-density LA mapping during high right atrial pacing was performed, gaining more than 2000 mapping points (average 3967±904). Isochronal activation maps were created using a 5-ms interval setting. The slow conduction zone (SCZ) was defined as a region with isochronal crowding of ≥3 isochrones within a 4-mm diameter tag, and an area containing ≥8 isochrones was defined as the conduction block zone (CBZ) (Figure). Conduction velocities correspond to ≤27 cm/s for SCZ and ≤10 cm/s for CBZ. The LA low-voltage area (LVA) was defined as a region ≤2 mV. Result During the follow-up period (33±23 months), AT occurred in 18 of 202 patients (9%), and AF recurred in 69 patients (34%). 190 of 202 patients showed SCZ, and 16 patients had CBZ. Elevated BNP level (201±192 vs. 123±129 pg/mL, p=0.0221) and CBZ (31% vs. 7%, P=0.0070) were associated with AT occurrence. In the multivariate analysis, only CBZ (odds ratio 4.65, p=0.0270) was associated with AT occurrence. SCZ was not associated with AT occurrence. Meanwhile, Non-paroxysmal AF (41% vs. 27%, P=0.0424), larger LA dimension (45±7 vs. 42±7 mm, P=0.0280), wider LVA (35±24 vs. 19±14 mm2, P=0.0072), and longer SCZ (68±46 vs. 56±37 mm, P=0.0514) were associated with AF recurrence. In the multivariate analysis, LA dimension (p=0.0424) was independently associated with AF recurrence. Conclusion A conduction block zone in the left atrium is associated with AT occurrence after catheter ablation for AF. Patients with CBZ may require additional induction and ablation for AT during the first AF ablation procedure.