<正>Objective:To evaluate the electrophysiological characteristics and radiofrequency catheter ablation of atrial tachycardia （AT） in patients with repaired atrial septal defects（ASD）. Methods: In 76 consecutive patients with AT who underwent the electrophysiological study and radiofrequency catheter ablation （RFCA）. 4 patients （one male and three female aged 35. 5±11. 5 years） had AT-related myocardial scar or incision. Earliest activation combined with entrainment mapping was adopted to determine a critical isthmus. Results: Re-entry related to the lateral atriotomy scar was inducible in 3 of 4 patients. With en-trainment mapping

the PPI-TCL difference was <30 ms when pacing at the inferior margins of the right lateral atriotomy scar. Among them

2 patients had successful linear ablation between scar area to inferior vena cava

and 1 patient between scar areas to tricuspid annulus. Re-entry involving an ASD patch was demonstrated in 1 of 4 patients. PPI-TCL differences <30 ms were found when entraining tachycardia at sites near the septal patch. But linear ablation failed in terminating AT. There was no complication during procedure. No recurrence of incision-related AT was found during follow-up except for the failed patient. Conclusion: Under conventional electrophysiological mapping

adopting linear ablation from scar area to anatomic barrier

successful ablation also can be obtained in patients with IRAT related to myocardial scar or incision.