Characterization of reentrant circuit in macroreentrant right atrial tachycardia after surgical repair of congenital heart disease - Isolated channels between scars allow "focal" ablation

Background-The purpose of this study was to characterize the circuit of mac roreentrant right atrial tachycardia (MacroAT) in patients after surgical r epair of congenital heart disease (SR-CHD). Methods and Results-Sixteen patients with atrial tachycardia (AT) after SR- CHD were studied (atrial septal defect in 6, tetralogy of Fallot in 4, and Fontan procedure in 6). Electroanatomic right atrial maps were obtained dur ing 15 MacroATs in 13 patients, focal AT in 1 patient, and atrial pacing in 2 patients without stable AT. A large area of low bipolar voltage (less th an or equal to0.5 mV) involved most of the free wall in all patients and co ntained 2 to 7 dense scars or lines of double potentials, forming 29 narrow channels (width less than or equal to2.7 cm) between scars in all but 1 pa tient, who had a single scar and only focal AT. All 15 MacroATs were propag ated through narrow channels. Ablation within the channel eliminated all 15 MacroATs with 1 to 3 (median I) radiofrequency applications. Ablation was performed in 9 other channels identified during MacroAT (5 patients) and in 5 channels identified during atrial pacing (2 patients). Conduction block was obtained across 28 of 29 channels. After ablation, reproducible sustain ed right AT was not induced in any patient. During follow-up (median 13.5 m onths), new MacroATs, atrial fibrillation, or palpitations occurred in 3 of 16 patients. Conclusions-MacroAT after SR-CHD requires a large area of low voltage conta ining greater than or equal to2 scars forming narrow channels. Ablation wit hin the channels eliminates MacroAT.