Catheter ablation for a right anteroseptal accessory pathway in a patient with an endocardial cushion defect.

We report a radiofrequency catheter ablation for atrioventricular reentrant tachycardia in a patient with a right anteroseptal accessory pathway complicating an endocardial cushion defect. His bundle potential was recorded 20 mm posterior to the accessory pathway. In the presence of associated congenital heart disease, it is very important to understand the anatomy of the conduction system prior to radiofrequency catheter ablation.