Relationship Between Complex Signal Identification and Non‐Pulmonary Vein Foci

Background 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. Methods 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. Results 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. Conclusions 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.