Predicting Ablation Difficulty for Idiopathic Ventricular Premature Contractions: The Role of the Distance Between Earliest Activation Sites Identified by Near-Field and First-Deflection Annotations

Background Catheter ablation is established for idiopathic ventricular premature contractions (VPCs), but elimination may be difficult when the arrhythmogenic substrate is deep within the myocardium. The spatial discrepancy between earliest activation sites identified by first-deflection (FD) and near-field (NF) annotations may represent a practical marker of ablation difficulty. Objective To evaluate whether the NF-FD distance predicts procedural complexity and ablation outcome in idiopathic VPC ablation. Methods We retrospectively analyzed 26 patients with idiopathic VPCs who underwent catheter ablation using the EnSite mapping system (Abbott, Abbott Park, IL, USA) with a high-density grid catheter. The NF-FD distance was calculated on the three-dimensional electroanatomic map. Results Acute success was achieved in 25 patients (96%). Patients with VPC elimination within 5 RF applications had a significantly shorter NF-FD distance than those requiring more (4.7 ± 4.5 mm vs. 20.3 ± 5.6 mm, P < 0.001). ROC analysis showed that NF-FD ≤8 mm predicted the composite endpoint of ≤5 applications and acute success with an AUC of 0.932 (95% CI: 0.837–1.000)) (sensitivity 0.90, specificity 0.86). NF-FD distance correlated significantly with RF applications (R = 0.771), ablation duration (R = 0.801), and total delivered energy (R = 0.816; all P < 0.001). NF-FD distance did not differ between chronic-phase success and recurrence groups (7.6 ± 8.1 mm vs. 10.0 ± 9.0 mm, P=0.352). Conclusion A longer NF-FD distance was associated with greater procedural difficulty; Chronic-phase success remained comparable when sufficient ablation was performed, suggesting that a long NF-FD distance should not discourage continued lesion delivery for durable VPC suppression.