Abstract

Introduction: Atrial arrhythmias are common complications in patients with surgically corrected congenital heart disease. Among them, macro-reentrant atrial flutter may involve both typical and scar-related atypical circuits, which increase diagnostic and therapeutic complexity.

Case presentation: A 52-year-old woman with a history of repaired partial atrioventricular septal defect was admitted with palpitations, dyspnea, and signs of acute heart failure. ECG showed persistent atrial flutter with WPW type B; echocardiography revealed reduced LVEF (36%). Ensite 3D mapping identified two independent macro-reentrant circuits: a scar-related flutter involving the right atrial lateral wall and a typical cavotricuspid isthmus–dependent flutter. Initial ablation from the inferior border of the lateral scar to the tricuspid annulus modified the flutter cycle length but failed to terminate the arrhythmia. Subsequent CTI ablation successfully restored sinus rhythm. A posterior septal accessory pathway was also identified and ablated.

Conclusion: Multiple forms of atrial flutter may coexist in patients with surgically repaired congenital heart disease. High-resolution 3D mapping enables accurate diagnosis and effective catheter ablation of these complex arrhythmias.