Balloon-shaped cystic subaortic membrane.

A 22-year-old man with a 4 month history of dyspnoea on exertion was referred for echocardiography. Transthoracic echocardiography revealed a balloon-shaped cystic mass (2 x 2 cm) attached to the left ventricular outflow tract (LVOT). Continuous-wave Doppler echocardiography showed a 44 mmHg mean LVOT gradient. The patient underwent transoesophageal echocardiography for detailed echocardiographic examination of LVOT and aortic valve. Transoesophageal echocardiography revealed a balloon-shaped cystic mass originating from the LVOT at the aorto-mitral communication. In the operating theatre, a cystic ballooning subaortic membrane was found and excised successfully. The morphology of the membrane was similar to that shown by transoesophageal echocardiography.