Slow conduction zone isolation as a procedural endpoint in ventricular tachycardia ablation guided by multimodal substrate assessment

Background

In recent years, several functional substrate assessment techniques have been developed to delineate potential isthmuses of scar-related ventricular tachycardia (VT). These approaches represent a paradigm shift compared with conventional strategies based solely on the identification of local abnormal electrogramas (LAVAs). It remains unclear whether ablation guided exclusively by abnormal LAVAs may also eliminate regions that require functional mapping techniques, such as isochronal late activation mapping (ILAM), for their identification. Moreover, there is no consensus regarding the optimal procedural endpoint for VT ablation guided by functional substrate analysis.

Objective

To evaluate the outcomes of scar-related VT ablation guided by multimodal substrate analysis, aiming for complete isolation of all identified slow conduction zones (SCZs).

Methods

Consecutive patients undergoing substrate-based VT ablation were included. Detailed substrate mapping was performed using double extrastimuli to identify SCZs, defined as regions exhibiting LAVAs and/or isochronal crowding (deceleration zones, DZs). The distribution of LAVAs and their relationship with DZs and mapped VT isthmuses were analyzed. The procedural endpoint was complete isolation of all SCZs, defined as elimination of LAVAs/DZs and loss of local capture.

Results

Thirty-six consecutive patients (75% ischemic cardiomyopathy, 94.4% male, 61.8 ± 13.1 years, LVEF 33.9 ± 13.5%) underwent substrate-guided VT ablation. After detailed mapping (4,370 ± 982 endocardial and 7,250 ± 1,325 epicardial points), 54 SCZs were identified (median 2 [1–3] per patient). All SCZs (100%) co-localized with LAVAs, and 41 (75.9%) overlapped with DZs. Twenty-seven VTs were mapped, of which 25 (92.5%) co-localized with SCZs. Mean RF application time was 17.6 (12–24) minutes. Complete SCZ isolation was achieved in 31 patients (86.1%; 96.2% of ischemic and 55.5% of nonischemic cases). Incomplete SCZ isolation was an independent predictor of VT recurrence.

At 13 ± 11 months of follow-up, overall VT-free survival was 72.2% (77.7% in ischemic and 55.5% in nonischemic cardiomyopathy). Overall survival was 94.4%. On multivariate analysis, complete SCZ isolation independently predicted lower VT recurrence (HR 0.47; 95% CI 0.21–0.94; P = 0.035).

Conclusions

Multimodal substrate analysis allows comprehensive evaluation of the arrhythmogenic substrate by integrating electrogram characterization with functional mapping data. Complete isolation of slow conduction zones is associated with significantly improved long-term VT-free survival.Slow Conduction Zone Isolation