Persistent atrial fibrillation (PersAF) electrogram-based ablation is complex, and appropriate identification of atrial substrate is critical. Little is known regarding the value of the average complex interval (ACI) feature for PersAF ablation.

To evaluate the value of ACI for discriminating active drivers (AD) from bystander zones (BZ), and for predicting AF termination and AF recurrence during PersAF ablation.

We included PersAF patients undergoing radiofrequency catheter ablation by pulmonary vein isolation and ablation of atrial substrate identified by spatiotemporal dispersion or complex fractionated atrial electrograms (>70% of recording). Operators were blinded to ACI measurement which was assessed for each documented atrial substrate area. AF Dominant Frequency (DF) was measured by Independent Component Analysis on 1-minute 12-Leads ECGs at baseline and after ablation of each atrial zone. AD were differentiated from BZ either by a significant decrease in DF (>10%), or by AF termination. Arrhythmia recurrence was sought during follow-up.

We analyzed 159 atrial areas (129 treated by radiofrequency) in 29 patients. ACI was shorter in AD than BZ (76.4±13.6 vs. 86.6±20.3ms; P=0.0055), and mean ACI of all substrate zones was shorter in patients for whom radiofrequency failed to terminate AF (71.3 [67.5–77.8] vs. 82.4 [74.4–98.5]ms; P=0.0126). AF recurrence was associated with more ACI zones with shortest value (3.5 [3–4] vs. 1 [0–1] zones; P=0.021). In multivariate analysis, ACI<70ms predicted AD (OR=4.02 [1.49–10.84], P=0.006) and mean ACI>75ms predicted AF termination (OR=9.94 [1.14–86.7], P=0.038) (Fig. 1).

ACI helps in identifying AF drivers and is correlated with AF termination and with AF recurrence during follow-up.