Introduction A 51-year-old man with Brugada syndrome (BrS) and spontaneous coved-type ECG (Figure 1A) was admitted for ICD implantation following out-of-hospital cardiac arrest due to ventricular fibrillation (VF). Given the dramatic event and high risk of VF recurrence, the previously asymptomatic patient asked about available treatment options. Anti-arrhythmic drug therapy (hydroquinidine) and epicardial ablation were discussed with the patient and he opted for catheter ablation.

Methods and Results After ICD implantation the patient underwent epicardial mapping of the right ventricle (RV). Using an anterior epicardial access, a steerable epicardial sheath (Agilis™ EPI) and a 3D mapping system (NavX, St. Jude Medical) with a linear multipolar mapping catheter (Livewire™), we performed voltage, activation and potential duration mapping of the RV epicardium. The baseline map (Figure 2A) revealed a small area with fractionated and prolonged potentials (duration > 110ms measured from QRS onset) over the RV outflow tract (RVOT). Interestingly, after an Ajmaline administration (30mg) and the induction of coved-type ECG in right precordial leads (Figure 2B) these potentials expanded both in duration and distribution extending down to the RV free wall (Figure 2B). Fractionated potentials with prolonged duration beyond the QRS end were targeted by ablation (30 Watts, irrigated radiofrequency) leading to further dramatic increase of ST-segment elevation during ablation (Figure 2C). Afterwards, another Ajmaline administration (30mg) induced coved-type ECG only in lead V1 (placed in 2nd intercostal space over the RVOT, Figure 2D) corresponding to residual prolonged and fractionated electrograms in the RVOT (Figure 2D). After re-ablation of these potentials a final re-map with Ajmaline (30mg) demonstrated a normal potential duration in the entire RV epicardium and only horizontal or ascending ST-segment elevation (Figure 2E). While the 12-lead ECG one day after ablation showed a round ST elevation in V1 and a horizontal (ascending) ST elevation in V2 (Figure 1B), the 12-lead ECG at three months follow-up was completely unremarkable (Figure 1C). ICD interrogation demonstrated freedom from VF and the patient continues to be free of any symptoms. Ajmaline challenge was offered but was denied.

Discussion Since the initial study by Nademanee et al. (Circ 2011) describing successful prevention of VF recurrence by catheter ablation of abnormal electrograms over the RVOT epicardium in BrS, Sacher et al. (HR 2014) and Brugada et al. (Circ EP 2015) demonstrated that sodium channel blockade can prolong the duration of abnormal epicardial electrograms and reveal an arrhythmogenic substrate extending beyond the RVOT. We present (1) re-induction of coved-type ECG by Ajmaline after epicardial ablation, caused by (2) residual abnormal electrograms in the corresponding epicardial RVOT region, and (3) disappearance of drug-induced coved-type ECG after abolition of the remaining epicardial substrate and (4) resolution of spontaneous coved-type ECG at three months follow-up.

Conclusion Catheter ablation of low-amplitude, high-frequency potentials with abnormally prolonged duration in the RV epicardium appears to be a safe and effective treatment for high-risk symptomatic BrS patients. In order to achieve complete substrate elimination, catheter ablation in BrS should be guided by repeated administration of Ajmaline to unmask the entire epicardial substrate.