Right Atrial Fibrosarcoma Mimicking Myxoma with Intermittent Complete Atrioventricular Block in a Young Adult: A Case Report

Abstract

Primary cardiac tumors are rare and may be associated with nonspecific symptoms and cardiac conduction disturbances. Preoperative imaging may not reliably distinguish benign from malignant cardiac masses. A 19-year-old man presented with progressive dyspnea, fatigue, and diaphoresis. Electrocardiographic assessment identified first-degree atrioventricular (AV) block with intermittent complete AV block. Transthoracic echocardiography revealed a 2 × 2 cm right atrial mass with a left ventricular ejection fraction of 65%, and cardiac computed tomography raised suspicion of myxoma. While awaiting surgery, the patient received dopamine at 15 μg/kg/min and oxygen at 3 L/min by nasal cannula. He underwent tumor excision with cardiopulmonary bypass and permanent pacemaker implantation. Intraoperative ventricular fibrillation caused cardiac arrest, for which defibrillation and adrenaline were administered. Histopathology was reported as low-grade fibrosarcoma. After three days of intensive care, he was discharged in stable condition on postoperative day four. A right atrial tumor clinically suspected to be myxoma was associated with advanced intermittent AV conduction disease and was subsequently reported as low-grade fibrosarcoma. This case emphasizes cardiac imaging, rhythm surveillance, histopathological assessment, and careful interpretation of perioperative outcomes.