MP-453092-5 ISOCHRONAL LATE ACTIVATION MAPPING FOR TARGETED ABLATION OF VENTRICULAR TACHYCARDIA IN PATIENTS WITH TETRALOGY OF FALLOT

Abstract

Patients with tetralogy of Fallot (ToF) have an increased risk of reentrant ventricular arrhythmias (VAs) utilizing slowly conducting anatomic isthmuses (SCAIs). Isochronal late activation mapping (ILAM) is an alternative mapping technique that identifies deceleration zones (DZ) during sinus and paced rhythms. These areas have been shown to be candidate sites for reentrant ventricular arrhythmias. Assess feasibility of ablation targeting DZs identified by ILAM during sinus and paced rhythms among patients with ToF and VAs. Patients ≥25 y/o with ToF and planned surgical or transcatheter pulmonary valve replacement (PVR) underwent ventricular stimulation study prior to PVR (PPVR EPS). Voltage maps and sinus/RV paced ILAM were created with high-density mapping catheters. SCAIs were defined as voltage <1.5 mV and <0.5 m/s between anatomic boundaries. Ablation of candidate DZ (>3 isochrones within 1 cm radius) was performed in all patients with inducible VT/VF. As able, activation mapping of VT was performed and successful ablation sites were compared with DZ locations for mechanistic correlation. Eighteen patients (median age 40.7 years [36-48], 56% female) underwent PPVR EPS. Ten (56%) had inducible VA. High-density mapping was performed with a mean of 5049 points [4580-5523] points in sinus rhythm, and 2518 [1615-3752] with RV pacing). A mean of 2 [1-3] DZ were identified per patient. DZ correlated with traditional SCAIs in 68% of patients. Alternate sites including anterior (20%) and lateral (12%) free-wall were also identified. Patients with inducible VA underwent ablation targeting bidirectional block across SCAIs (successful in 97%) and covering of non-SCAI DZ areas. Seven patients (70%) were non-inducible following ablation. Activation mapping could be performed in two patients with successful termination at DZ in both patients (one SCAI and one anterior RV DZ). No sustained ventricular arrhythmias have been detected at 9 [2-16] months follow-up. Isochronal late activation mapping identifies functional substrates for VT during sinus and paced rhythms and guides targeted ablation in ToF with VA. Regions with isochronal crowding correlated with SCAIs while also identifying alternative sites predictive of ablation success.