Ventricular Tachycardia Substrates in Patients after Repaired Tetralogy of Fallot

Background: Patients after repaired Tetralogy of Fallot (rTOF) have an increasing risk of ventricular tachycardias (VT). Monomorphic VT in this patient population is in the majority of cases related to slow conducting anatomic isthmuses (SCAI). We report our data of risk stratification in this patient population.

Methods: All patients with rTOF undergoing electrophysiological study with risk stratification for VT from January 2019 until September 2023 were included. In all procedures right ventricular voltage and activation mapping during sinus rhythm was performed to identify SCAI (conduction velocity <0,5 m/s) prior to VT induction (up to S4 180 milliseconds). If induced VT was hemodynamically tolerated activation mapping during VT was performed. Ablation was performed with an open irrigated tip catheter.

Results: A total of 41 procedures in 39 patients (mean age 43 years, 15 females) were performed. In primary procedures SCAI were present in 29 patients (74%). VT was only inducible in patients with SCAI (15/29 (52%), thereof 2 different VTs in 4 patients). Ablation was performed in 32 procedures (29 primary procedures with SCAI, one procedure without SCAI, but extended scar and 2 secondary procedures). Ablation was performed of isthmus 3 (between the pulmonary valve and the VSD patch) in 31/32 procedures, isthmus 4 (between the VSD patch and the tricuspid anulus) in 30/32 procedures, isthmus 1 (between the right ventricular incision and the tricuspid anulus) in 4/32 procedures, and isthmus 2 (between the pulmonary valve and the right ventricular incision) in 4/32 procedures. Ablation of all VTs was possible in 13/15 patients (87%). In the remaining two patients after unsuccessful procedure and one other patient ICD-implantation was recommended/performed. During a mean follow-up of 19.5 months only one patient had recurrence of sustained VT/VF (a patient with unsuccessful ablation of SCAI 3 because of implanted melody valve prior to ablation and consecutive ICD implantation). No complications occurred.

Conclusion: SCAI were present in the majority of patients after rTOF. The most frequent SCAI were isthmus 3 and isthmus 4. The success rate of 87% was high and recurrence of VT/VF occurred only in one patient after unsuccessful ablation. ICD implantation was indicated in 3/39 patients.

Publication History

Article published online:
13 February 2024