Surgical ablation of AT or atrial flutter can be effective in ACHD patients undergoing planned surgical repair.497 508 See Online Data Supplement 20. In patients with symptomatic SVT undergoing planned surgical repairs of structural heart disease or ischemic heart disease, observation studies report that arrhythmia surgery can be integrated into the operation with high efficacy and without increased surgical morbidity.497 500 In populations including those with tetralogy of Fallot/double-outlet right ventricle, tricuspid valve repairs, and ASD, rates of freedom from recurrent AT or atrial flutter have been reported as 73% to 93% without antiarrhythmic medications during medium-term follow-up of 2.5 to 10 years. Catheter ablation may be attempted in specialized centersbefore surgical Fontan repair. There are no RCTs comparing efficacy of catheter versus surgical ablation of AT or atrial flutter in patients with prior Fontan repairs. The incidence of AT or atrial flutter in patients with prior Fontan repairs approaches 60% and increases with advancing age. Catheter ablation success rates in this subset of patients are lower than for other lesions,457 with acute success in 54% to 75%, and with recurrent AT in 27% to 50% of patients within 2 to 4 years490,495 ; death or transplantation was reported in 27% during follow-up. Several observational studies of surgical resection and ablation for AT or atrial flutter associated with Fontan conversion reported rates of freedom from AT of 12% to 16% during follow-up extending to 8 years501 505 ; death or transplantation was reported in 6% to 14% during follow-up. Performance of a modified right atrial maze procedure versus CTI ablation was associated with lower recurrence rates.501 Alternatively, surgical repairs without arrhythmia intervention are associated with high recurrence rates of AT. 