Abstract
BACKGROUND: The 'univentricular' heart encompasses a variety of congenital cardiac defects characterized by a single functional ventricle and an underdeveloped ventricular chamber. Surgical intervention, typically in infancy or childhood, aims to regulate pulmonary blood flow volume. In adulthood, untreated patients may experience limitations in physical activity and elevated morbidity due to persistent cyanosis and arrhythmias, notably after the Fontan procedure. CASE SUMMARY: A 38-year-old Mexican man with an unrepaired morphologically right single ventricle and a common atrium presented with palpitations. Diagnostic imaging revealed a hypertrophic systemic single ventricle with severe atrioventricular valve regurgitation and pulmonary stenosis. Despite ongoing anticoagulant and beta-blocker therapy, persistent symptoms prompted catheter ablation guided by CARTO-Merge(®), a function that overlays computed tomography or magnetic resonance imaging onto a CARTO(®) electroanatomical map. Ablation along the cavo-annular isthmus was successfully performed, achieving arrhythmia termination. Post-ablation, the patient developed sinus rhythm and second-degree atrioventricular block, necessitating the implantation of an epicardial pacemaker. DISCUSSION: Atrial flutter ablation in univentricular hearts without prior surgery is rare. Such patients are predisposed to post-Fontan arrhythmias, often requiring intervention due to increased morbidity. Atrial flutter arises from scarred post-surgery regions, necessitating careful assessment and management. Our case demonstrates successful ablation in a complex congenital heart condition, highlighting the importance of comprehensive imaging, understanding arrhythmia mechanisms, and meticulous procedural techniques for optimal outcomes.