When the Heart Pays for the Chest: A Case Report of an Extracardiac Mediastinal Mass Presenting With Cardiac Arrhythmias.

Mediastinal masses are an uncommon finding in the emergency department and cause a variety of symptoms and presentations. Cardiac arrhythmias represent a rare complication that may reveal these tumors, particularly through cardiac compression. We report the case of a 40-year-old patient with a past medical history of a primary mediastinal hepatoid adenocarcinoma treated with chemotherapy. The patient was admitted to the emergency department with palpitations occurring with changes of position. Upon further investigation and initial treatment with an oral beta-blocker, the patient had an enormous anterior and middle mediastinal mass extending vertically across all three anatomical levels, with significant mass effect on cardiac structures explaining his dysrhythmia occurring at the change of position. Given the size of the mass and its close relationship to surrounding structures, the patient was started on chemotherapy while continuing beta-blocker therapy. Palpitations are most often a symptom of a benign underlying condition; however, they can also be a sign of potentially serious and life-threatening diseases, and hence a thorough investigation is important.