Moving the Goalposts

Atrial arrhythmias have for decades been recognized as a principal late complication of the Fontan procedure. A specific connection between the 2 was recognized soon after the procedure emerged as a standard clinical pathway for patients with single ventricle physiology. Intra-atrial reentrant tachycardia (IART) is a major cause of morbidity in the form of recurring symptoms and need for medical intervention in these patients. Early on, risk factors for future IART were identified, most notably the occurrence of atrial arrhythmia in the perioperative period. The relationships between organized atrial tachycardias and comorbidities such as thromboembolism, heart failure, and mortality have been investigated and are now well established. These observational associations were established through retrospective studies, which could not allow for attribution of causality. Despite this weakness of this type of clinical evidence, IART has been clearly identified in multiple concordant studies as one of the bad actors predictive of poor long-term outcome in patients undergoing the Fontan procedure.