Atrial tachycardia originating from an incompletely isolated box lesion in a patient undergoing thoracoscopic left atrial appendectomy and surgical ablation for long-standing persistent atrial fibrillation.

The efficacy of pulmonary vein isolation for persistent atrial fibrillation or long-standing persistent atrial fibrillation is limited. Thoracoscopic surgical ablation was introduced as an alternative treatment, but additional catheter ablation is needed to treat postoperative atrial tachycardia in some cases. Little is known about electrophysiological characteristics or mapping techniques of recurrent tachycardia after total thoracoscopic surgical ablation and left atrial appendectomy. A 63-year-old man underwent catheter ablation of atrial tachycardia after total thoracoscopic left atrial appendectomy and surgical ablation of atrial fibrillation lasting longer than 5 years. Catheter ablation was performed using a three-dimensional mapping system. Electroanatomical mapping outside the box lesion revealed a centrifugal activation pattern with the origin located at the gap of the roofline, and further activation mapping inside the box lesion was conducted again with the reference catheter positioned at the left atrial posterior wall, which revealed localized reentrant atrial tachycardia. Atrial tachycardia was smoothly treated with activation mappings. This case indicated the utility of activation mappings separating outside the box lesions from inside the box lesions. <Learning objective: Electroanatomical mapping outside a box lesion might help to ablate postoperative atrial tachycardia in a patient undergoing surgical box isolation, and reentry localized in the left atrial posterior wall could be visualized using a three-dimensional mapping system with the reference catheter positioned at the box lesion. Confirmation of a completely isolated box lesion is vital, because such patients have a sufficiently enlarged left atrium that has the arrhythmogenicity to maintain atrial tachycardia.>.