Atrialized right ventricular chamber as a source of ventricular tachycardia in Ebstein's anomaly. Analysis of two successful catheter ablation cases Carla Losantos, MD, Guillermo Muñoz, MD, Manlio F. Márquez, MD, Jorge Gómez, MD, Moises Levinstein, MD, Santiago Nava, MD ⁎ Electrocardiology Department, National Institute of Cardiology Ignacio Chavez, Mexico City, Mexico abstract article info Available online xxxx Keywords: Ventricular tachycardia Congenital heart disease Ebstein's anomaly Catheter ablation Ventricular tachycardia in Ebstein's anomaly patients is rare and increases the risk of sudden death up to 6 times. We present two cases of Ebstein's anomaly, the first of them with a history of Glenn surgery and biological prosthesis at tricuspid position and the second case without surgical repair. Both admitted to the emergency room due to ventricular tachycardia poorly tolerated. Detailed substrate characterization and pace mapping showed fragmented signals in the area of atrialized right ventricle and correlated were pace mapping reproduced morphology identical to the clinical VT, ablation at this sites were successful without recurrence during follow-up. © 2020 Elsevier Inc. All rights reserved. Introduction Ebstein's anomaly (EA) is a congenital heart disease (CHD) charac- terized by dysplasia and apical displacement of the septal leaflet of the tricuspid valve, and subsequently right ventricular atrialization [2]. The incidence of ventricular arrhythmias in CHD patients is estimated in 0.1 to 0.2% per year [3]. In EA ventricular tachycardia (VT) is rare, de- scribed in around 2% of patients [1]. Data on clinical and electrophysio- logical characteristics of VT in EA patients is scant. We present two cases of EA and VT with a left bundle branch block (LBBB) morpohology suc- cessfully treated with catheter ablation. Case 1 A 15-year-old boy with EA and atrial septal defect type ostium secundum that was surgically treated with a Glenn anastomosis, and tri- cuspid valve replacement at 10 years of age, was admitted to the ER due to fast palpitations. A wide QRS complex tachycardia at 180 bpm with LBBB morphology and extreme axis deviation was documented (Fig. 1A); due to poor hemodynamic tolerance, it was electrically cardioverted. Because of the Glenn anastomosis an ICD implant was consider unsuitable and patient was taken to the EP lab for radiofre- quency catheter ablation (RFCA). Clinical VT was induced with programed electrical stimulation (PES) at right ventricular (RV) apex, and poorly tolerated requiring electrical cardioversion after brief local activation mapping. Substrate mapping with CARTO XP system identi- fied a wide area of low and fragmented potentials at the basal aspect of the RV near the TV in the atrialized right ventricle (ARV) Fig. 2A. Care- ful pace mapping at sites of scar and fragmented signals was performed until a 12 out of 12 match was achieved with a latency of stimulus to ECG similar to local electrogram to ECG at the site of earliest recording (Fig. 2B) (no matching system was available at that time). A line of ab- lation was then performed at this site with no VT induction afterwards. Patient has remained asymptomatic after 10 years of follow up. Case 2 A 48-year-old female with EA and 56% of atrialized RV, with a previ- ous history of three VT episodes despite treatment with amiodarone, was taken to the EP lab for RFCA. Electrocardiogram during tachycardia showed a regular broad QRS complex tachycardia at 140 bpm with LBBB morphology, negative concordance at precordial leads and left axis de- viation (Fig. 1B). Clinical VT was induced with PES, poor hemodynamic tolerance was observed but VT resumed spontaneously. A substrate mapping with CARTO 3 system was performed identifying a wide area of scar and fragmented signals in the ARV (Fig. 3A) and voltage map in sinus rhythm showing late potentials and fragmentation in scar area (Fig. 3B). Pace mapping with Passo® was performed near the Journal of Electrocardiology 62 (2020) 165–169 Abbreviations: ARV, atrialized right ventricle; CA, catheter ablation; CHD, congenital heart disease; EA, Ebstein's anomaly; ER, emergency room; LBBB, left bundle branch block; RFCA, radiofrequency catheter ablation; RV, right ventricular; RVOT, right ventricular outflow tract; SCD, sudden cardiac death; VT, Ventricular Tachycardia; PES, programed electrical stimulation. ⁎ Corresponding author at: National Institute of Cardiology Ignacio Chavez, Juan Badiano, 1, Col. Sección XVI, C.P. 14080 Ciudad de Mexico, Mexico. E-mail address: santiagonavat@hotmail.com (S. Nava). https://doi.org/10.1016/j.jelectrocard.2020.08.006 0022-0736/© 2020 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect Journal of Electrocardiology journal homepage: www.jecgonline.com