Rare cause of atrial fibrillation: a thymic mass.

A 62-year-old African-American man admitted to the emergency room with chest pain and exertional dyspnoea. He was found to be in rapid atrial fibrillation with pulmonary oedema. A transoesophageal echocardiogram performed prior to cardioversion showed a depressed left ventricular function (ejection fraction 30%) and an extracardiac heterogeneous echodensity compressing the right atrium and the superior vena cava. CT of the chest confirmed an anterior mediastinal mass measuring 13.5×6.6×10.1 cm, exerting a mass effect on the right atrium with mediastinal and right hilar adenopathy. CT-guided biopsy of the mediastinal mass revealed thymic carcinoma (squamous cell subtype). The metastatic workup was negative. The mass was deemed surgically unresectable due to its proximity to the heart. Chemotherapy was initiated with carboplatin/paclitaxel every 3 weeks with plans for intensity modulated radiotherapy after one to two cycles of chemotherapy. The patient recently had a repeat CT scan of the chest showing regression of the tumour.