The Long Shadow of Repair: Late-Onset AV Block and Atrial Arrhythmias After Scimitar Syndrome and Mitral Annuloplasty

Background and Clinical Significance: Scimitar Syndrome is a rare congenital cardio-pulmonary anomaly characterized by partial anomalous pulmonary venous return, often requiring early surgical correction. It may coexist with other congenital or acquired cardiovascular anomalies, including valvular diseases such as mitral regurgitation. When this intervention is combined with mitral valve annuloplasty, the proximity to the atrioventricular node may predispose patients to late-onset conduction disturbances. Case Presentation: We describe the case of a 53-year-old male who developed paroxysmal atrial fibrillation, atrial flutter, and intermittent second-degree AV block decades after un-dergoing surgical correction of Scimitar Syndrome with concomitant mitral annuloplasty. Multimodal echocardiographic evaluation revealed preserved left atrial volume, normal intra-atrial conduction time, mildly reduced strain, and maintained atrial synchrony. The patient was treated with direct oral anticoagulants, beta-blockers and underwent im-plantation of a ventricular leadless pacemaker. Conclusions: This case highlights the role of atrial function imaging in guiding rhythm management and procedural choices in surgically-corrected congenital heart disease.