A 66-year-old female with a history of hypertension presented for an elective transthoracic ultrasound. The study revealed normal left and right ventricular size and function and an echogenic band running along a normally sized left atrium. Subsequently a transesophageal echocardiogram (TEE) was organised which revealed a thin partial membrane arising from the roof of the left atrium (LA) and extending across to the interatrial septum (IAS) ( Fig. 1A, B, C and D ). Colour Doppler imaging revealed unidirectional, laminar flow through the membrane ( Fig. 1E and F). The remainder of the study was unremarkable, with normal left and right ventricular function and absent valvular pathology.