Relationship Between Complex Signal Identification and Non-Pulmonary Vein Foci

Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation; however, recurrences often originate from non-pulmonary vein (non-PV) foci. The Complex Signal Identification (CSI) algorithm in CARTO 3 assigns electrogram-fractionation scores (0-10). This study evaluated the feasibility of CSI-assisted mapping for identifying non-PV triggers.

We retrospectively analyzed 23 consecutive patients undergoing first-time AF ablation between January and June 2024. After PVI, non-PV triggers were induced using isoproterenol and adenosine triphosphate (ATP). When ectopy was absent, rapid pacing during isoproterenol infusion followed by defibrillation was performed, and ATP testing was repeated. High-density CSI mapping was conducted during sinus rhythm or high right atrial pacing using system default settings, targeting atrial components after ventricular blanking.

A total of 33 non-PV foci were localized (20 left atrium [LA], 13 right atrium [RA]). The mean CSI scores of LA and RA foci were 9.0 ± 2.3 and 8.8 ± 2.7, respectively. ROC analysis showed an AUC of 0.917 for discriminating non-PV foci, with an optimal cutoff of 8.5 (sensitivity 87.9%, specificity 88.3%). At 12 months, arrhythmia-free survival was 82.4% under symptom-driven follow-up. Ablation was selectively performed at the earliest activation and adjacent high-CSI points, avoiding indiscriminate lesion delivery.

CSI-assisted mapping provided practical, adjunctive guidance to provocation and activation mapping for non-PV focus localization. While apparent discrimination was promising, the 8.5 threshold remains exploratory. Larger multicenter studies with standardized CSI settings and systematic post-ablation assessment are warranted to validate these preliminary findings.