Man in his 40s with palpitations

A man in his 40s was admitted to our hospital after an enlarged heart was incidentally discovered at a local hospital during a routine medical evaluation for palpitations lasting 4 months. Physical examination and laboratory investigations were unremarkable. Transthoracic echocardiography revealed a large, well-circumscribed cystic mass in the mediastinum, measuring approximately 121×96 mm. Scattered floating echogenic foci were observed within the lesion. The mass exerted extrinsic compression on the right atrium, resulting in increased intracavitary flow velocity, with a peak velocity of 131 cm/s and a corresponding pressure gradient of 7 mm Hg. The echocardiographic and non-enhanced chest CT findings are shown in figure 1.