Ventricular location of a part of the right atrial isthmus after tricuspid valve replacement for Ebstein's anomaly: a challenge for atrial flutter ablation.

We report the case of a patient with atrial flutter late after tricuspid valve replacement for Ebstein's anomaly. Computed tomographic angiography revealed that coronary sinus ostium and part of the right atrial isthmus were located on the ventricular side of the valve ring due to the specific surgical approach in this condition. Based on the results of electroanatomic mapping and entrainment, the arrhythmia was found to be cavotricuspid isthmus dependent clockwise atrial flutter. Completion of the isthmus line required ablation lesions across the artificial valve. When these were delivered the arrhythmia terminated and isthmus block was achieved. Due to arrhythmia recurrence a redo procedure was performed which demonstrated conduction recovery in the ventricular part of the cavotricuspid isthmus. Intracardiac ultrasound-guided ablation successfully eliminated conduction across the isthmus with subsequent freedom from arrhythmia on follow up.