Document resource
Introduction Adults with repaired tetralogy of Fallot (rTOF) have a lifelong risk of ventricular tachycardia (VT) and sudden cardiac death (SCD). VT is related to defined anatomical isthmuses from morphological and surgical conduction barriers. Published risk scores report accurate prediction of high-risk patients. Catheter ablation of these isthmuses, particularly between the VSD patch and pulmonary valve (isthmus-3), is reported to substantially reduce ventricular arrhythmia with consideration of deferral of defibrillator (ICD) implantation in selected patients. However, uncertainty remains in longer-term ablation outcomes with no data on risk score performance in rTOF patients presenting with VT.Methods Adults with rTOF at a single ACHD centre presenting with documented VT who underwent VT ablation between 2000-2024 were retrospectively reviewed. Clinical data, procedural reports and electro-anatomical maps were reviewed. VT ablation was performed as per published protocols with VT stimulation and activation mapping guided ablation and substrate based ablation in patients without inducible VT. Success included VT non-inducibility and/or conduction block across the targeted isthmus in patients without inducible VT. VT recurrence and mortality were recorded and the predictive performance of six risk scores/guidelines was assessed.Results 13 patients (85% male, median age 43 years) underwent 19 catheter-based ablations with a median follow-up over 88 months (IQR 13-178). VT was inducible in 12 patients (63%) with activation mapping demonstrating an isthmus-3 dependent circuit in 6 (50%), isthmus 1,2 or 4 circuit in 5 (42%) and an unconventional VT circuit (‘non-isthmus’) in 1 patient. Isthmus-3 was part of the ablation strategy in 12 patients (63%).Ablation was acutely successful in 15 patients (80%) with better outcomes in isthmus-3 ablations (92%) compared to isthmus 1,2 or 4 (50%, χ2 = 4.02, p=0.045). VT recurred during follow-up in 12 patients (63%) with lower recurrence following isthmus-3 ablations (50%) compared with isthmus 1,2 or 4 ablations (100%; χ2 = 5.73, p = 0.017). The single non-isthmus ablation was acutely successful without VT recurrence (figure 1). All patients with an acutely unsuccessful ablation had VT recurrence. There was one death with ICD therapy refractory VF.Risk score prediction for VT was unreliable and inconsistent ranging from 0/19 (Khairy, Prevention-ACHD) to 15/19 (Spanish-ACHD) with none predicting the whole cohort. All patients had at least one risk score that predicted an intermediate or high risk of VT or SCD (figure 2).Conclusions VT ablation in rTOF has a high acute success, particularly with isthmus-3, however VT recurrence remains common in the intermediate-term and deferral of ICD implantation should be highly selected. Risk score performance was sub-optimal and inconsistent at identifying this high-risk cohort. Use of multiple scoring criteria and adjunctive strategies is strongly recommended.Abstract 522 Figure 1Abstract 522 Figure 2