Atrial tachycardia ablation through the sub-pulmonary ventricle in a patient with multiple malformations associated with congenitally corrected transposition of the great arteries and double-sided slow-pathway.

A 46-year-old woman with congenitally corrected transposition of the great arteries (ccTGA) associated with dextrocardia, situs viscerus inversus, and left superior vena cava persistence presented with an incessant supraventricular tachycardia. Electrophysiological study was not conclusive in differential diagnosis of atrial tachycardia versus atypical atrioventricular (AV) nodal reentrant tachycardia, also due to the unconventional anatomy of the coronary sinus. By a comprehensive mapping of cardiac chambers, a double side slow-pathway was localized in both atrial chambers and subsequently ablated by radiofrequency delivery without tachycardia changes. Aortic root and cusps were devoid of electrical activity. The muscular part of the sub-pulmonary ventricle at the level of interatrial septum showed an earliest activation signal of -90 ms and ablation of this site was effective in abolish the tachycardia. This is the first case to report technical concerns of septal atrial tachycardia ablation in ccTGA associated with multiple anatomical malformations. Moreover, some peculiarities have been reported for the first time including the presence of double-side AV nodal slow-pathway and atypical localization of the tachycardia origin into the muscular part of the sub-pulmonary ventricle instead of posterior pulmonary cusp.