Atypical twin atrioventricular nodal re-entrant tachycardia in a congenitally corrected transposition of the great arteries patient with a surgical repair of a ventricular septal defect: a case report

Background: Twin atrioventricular (AV) nodal tachycardia is a rare mechanism of supraventricular arrhythmia, only seen in some specific congenital heart defects (CHD). It consists of a re-entrant circuit between two distinct AV nodes (anterior and inferior). Since both nodes have antegrade and retrograde conduction, there is usually two QRS morphologies in sinus rhythm.

Case summary: This case is about an atypical twin AV nodal tachycardia in a 15 years old patient with congenitally corrected transposition of the great arteries and previous history of a ventricular septal defect repair. The surgical closure was probably responsible of a poor antegrade conduction over the inferior AV node, which was responsible for a unique QRS morphology. He finally received a catheter ablation of the inferior AV node. He remained asymptomatic without anti-arrhythmic drugs at 8-months post-ablation.

Discussion: Twin AV nodal re-entrant tachycardia is a rare phenomenon. The presentation and electrophysiological study can be both atypical due to previous surgical repair. The operator should be aware of specific CHD where twin AV nodal re-entrant tachycardias are expected.