Anterior Mediastinal Mass Causing Intermittent Atrial Fibrillation.

Mediastinal masses are a rare finding in the emergency department and typically present with vague chest complaints such as chest discomfort, chest pain, or dyspnea. Rarely do these tumors present with dysrhythmias, and when dysrhythmias are present, they typically arise secondary to endocrine or metabolic effects exerted by the tumor. Here we report a case of a patient who presented to the emergency department with atrial fibrillation with rapid ventricular response, concomitant with a history of recurrent palpitations that were previously aborted with self-induced vagal maneuvers. Upon further investigation, the patient had an anterior mediastinal mass, diagnosed as a thymoma, suspected to be contributing to his presenting dysrhythmia through mass effect.