We present the case of a 23-year-old male diagnosed with a complex congenital heart disease (with single ventricle physiology) which necessitated many surgical interventions including total cavopulmonary connection. The patient presents with recurrent (almost daily) highly symptomatic atrial tachycardia with rapid ventricular rate and poor haemodynamic tolerance. Due to failure of antiarrhythmic drug therapy the patient was referred for catheter ablation. Atrial access was provided following transconduit puncture with a standard transseptal set. Crossing to the atrium with the transseptal introducer was not successful due to resistance from the conduit and the atrial wall. Therefore, balloon dilation of the puncture using a cutting balloon was carried out which resulted in easy crossing to the atrium with a steerable transseptal introducer. Several atrial tachyarrhythmias were induced two of which allowed mapping demonstrating a macroreentrant tachycardia dependent on the cavoannular isthmus as well as a complex fi gure-of-eight circuit involving right pulmonary veins and the right atrial appendage. Linear lesions transecting the critical isthmuses of the two circuits were delivered which rendered the patient noninducible. During a 9-month follow-up period the patient remained arrhythmia free.