Twin Atrioventricular Nodes Connecting to Sling of Conduction Tissue in Congenitally Corrected Transposition Associated With Straddling Tricuspid Valve

This report describes a case of reentrant supraventricular tachycardia relating to “twin” atrioventricular nodes in a 6-year-old female patient with congenitally corrected transposition of the great arteries associated with straddling tricuspid valve. Straddling and overriding of the tricuspid valve literally or by definition indicate malalignment of the inlet part of the ventricular septum and atrial septum by an abnormally large ventriculoatrial septal angle. Therefore, anterior atrioventricular conduction tissues are expected in this setting; however, the present report describes an exception to the rule that combination of straddling tricuspid valve is unlikely to be associated with twin atrioventricular nodes/sling. The patient underwent successful ablation of one atrioventricular node, eliminating the tachycardia, and subsequently Fontan-type palliation.