Mechanism and mapping of atrial arrhythmia in the modified Fontan circulation

The Fontan circulation has been a major success in the management of patients with functionally single-ventricle cardiac lesions, although arrhythmia remains one of the major complications in the long term and historically has been difficult to treat. The electrophysiologic substrate within the right atrium is complex, with areas of scarring and/or anatomic structures acting as central barriers to conduction in reentrant circuits, which may be mechanistically and anatomically different from typical atrial flutter. Developments in three-dimensional mapping have improved our understanding of different arrhythmia mechanisms, which is fundamental to developing a better strategy for arrhythmia ablation using percutaneous techniques.