Age-Related Ventricular Tachycardia Substrate Characteristics for Repaired Tetralogy of Fallot Before Transcatheter Pulmonary Valve Placement.

Background: Ventricular tachycardia (VT) substrate characteristics before transcatheter pulmonary valve replacement (TPVR) in repaired tetralogy of Fallot (rTOF) are unknown.

Objectives: In this study, the authors sought to evaluate substrates for sustained monomorphic VT before TPVR in rTOF.

Methods: Retrospective (2017 to 2021) and prospective (commencing 2021) rTOF patients with native right ventricular outflow tract referred for electrophysiology study (EPS) before TPVR were included. Electrophysiologic findings and outcomes of VT ablation were determined.

Results: One-hundred eighty patients (mean age 39 ± 14 years, 54% male, 71 retrospective, 109 prospective) were identified. At EPS, monomorphic VT was induced in 45 (25%), and a slowly conducting anatomic isthmus alone was observed in 40 (22%). VT isthmus conduction velocity decreased (-0.08 m/s per decade; P = 0.008) and VT inducibility (P < 0.001 for trend) and cycle length (CL) (+15 ms per decade, P = 0.005) increased with age. Multivariable factors associated with shorter VT CL included preserved isthmus conduction velocity (-50 ms per m/s; P = 0.02), absence of atrial flutter (-18 ms; P = 0.007), and improved RV ejection fraction (-16 ms per 10% increase; P = 0.007). Catheter ablation was acutely successful in 80/83 (96%). At repeated EPS after a median of 5 months, previously ablated substrates were evident in 3/24 (13%) and new VT substrates in 3/33 (9%).

Conclusions: Pre-TPVR VT substrates in rTOF demonstrate age-related degeneration that was associated with VT inducibility and VT CL. Both recovery of VT isthmus conduction and new VT substrates were observed after TPVR despite successful catheter ablation.