Beyond rhythm disorder: a rare case report of a young patient with mediastinal bronchogenic cyst

Background: Mediastinal bronchogenic cysts are sporadic congenital tumors, accounting for approximately 10%-15% of all mediastinal masses. In most cases, they remain asymptomatic. We present a case of a young man with new-onset atrial fibrillation caused by extra cardiac compression of the left atrium by mediastinal bronchogenic cyst. We report the first documented case in our country of a patient with a mediastinal bronchogenic cyst presenting with cardiac symptoms. Case summary: A 39-year-old man was admitted to the emergency department with palpitations, dyspnea, and tachycardia that developed after physical activity. Electrocardiography demonstrated the first episode of atrial fibrillation. Echocardiography revealed an oval echolucent mass compressing the left atrium. Cardiac magnetic resonance imaging showed a massive mediastinal bronchogenic cyst causing compression of the left atrium, right inferior pulmonary vein, and esophagus, which was displaced to the left side. Robot-assisted thoracoscopic surgery was planned and performed successfully. Discussion: Although typically asymptomatic, bronchogenic cysts can acutely present with life-threatening complications, particularly when they compress important cardiovascular structures. This case highlights the important role of comprehensive evaluation in young patients. It is crucial to consider extra cardiac causes in new-onset atrial fibrillation, especially in young adults. Fast and accurate diagnosis is essential to prevent further complications, with management extending beyond restoring sinus rhythm.