Discussion

Ventricular tachycardia is rarely documented in Ebstein’s anomaly. ^{Reference Walsh2–Reference Shivapour, Sherwin and Alexander4} Shivapour et al reported that only 3 of 74 patients (4%) with an Ebstein’s anomaly undergoing a Cone procedure had sustained monomorphic ventricular tachycardia. ^{Reference Shivapour, Sherwin and Alexander4} Ventricular tachycardia may be associated with complex congenital heart diseases, especially following surgical ventriculotomies. ^{Reference Zeppenfeld, Schalij and Bartelings1} Reentry circuit isthmuses of ventricular tachycardia are often located within anatomically defined isthmuses bordered by unexcitable tissue, such as a patch in the right ventricular outflow tract or tricuspid valve. ^{Reference Zeppenfeld, Schalij and Bartelings1} Linear ablation of the isthmus is necessary to eliminate the ventricular tachycardia in this situation. On the other hand, the point catheter ablation technique for macro-reentrant ventricular tachycardia has rarely been reported and drawing an entire activation map of the ventricular tachycardia could be avoided. ^{Reference Shoda, Kasanuki and Ohnishi5} Moving a mapping catheter from the systolic phase to the diastolic phase is useful to detect the area of diastolic fragment potentials, which is an appropriate ablation target. If the phenomena of concealed entrainment and a post pacing interval equal to the cycle length of the ventricular tachycardia are defined, the point ablation technique could be utilised. ^{Reference Shoda, Kasanuki and Ohnishi5}

A prior histologic evaluation of the atrialised right ventricle in Ebstein’s anomaly has demonstrated clusters of cardiomyocytes isolated by fibrotic networks. ^{Reference Anderson and Lie6,Reference Frescura, Angelini and Daliento7} Circuits of ventricular tachycardia are likely to be intrinsic to the congenitally abnormal atrialised right ventricle or hypoplastic right ventricle and are a consequence of degenerative remodelling. Moore et al demonstrated that ventricular arrhythmia substrates were localised to the atrialised right ventricle in un-operated patients with Ebstein’s anomaly. ^{Reference Moore, Shannon and Gallotti3} They also reported focal ventricular tachycardia in eight patients and macro-reentrant ventricular tachycardia in four; however, the efficacy of the point ablation for macro-reentry was not well described. In our case, the tachycardia circuit was eliminated by a single point catheter ablation at an area with diastolic fractionated potentials. The boundary between the atrialised right ventricle and hypoplastic right ventricle can be identified with 3D substrate mapping. Recorded potentials in the atrialised right ventricle differ from those in the hypoplastic right ventricle.

Ebstein’s anomaly is characterised by apical displacement and dysplasia of the septal leaflet of tricuspid valve with a right ventricular atrialisation compromising its function. The functional part of the right ventricle is often small and ill-equipped to maintain a full cardiac output, especially in patients with Ebstein’s anomaly with pulmonary atresia. The choice of surgery for patients with a small functional right ventricle might be a single-ventricle repair. ^{Reference Shinkawa, Polimenakos and Gomez-Fifer8} After a total cavopulmonary connection operation, access to the right ventricle is difficult because it should be approached using a conduit puncture or transaortic procedure. Hence, ventricular tachycardia substrates should be eliminated before a total cavopulmonary connection.

We reported a successful point ablation in a case with Ebstein’s anomaly and pulmonary atresia associated with a sustained macro-reentrant ventricular tachycardia and history of a ventriculotomy. The ventricular tachycardia substrate and slow conduction zone existed in a low voltage area between the atrialised right ventricle and hypoplastic right ventricle.