Flail subaortic membrane mimicking left ventricular outflow tract obstruction in hypertrophic cardiomyopathy.

A subaortic membrane is an uncommon cause for left ventricular outflow tract obstruction. Hypertrophic cardiomyopathy with dynamic left ventricular outflow tract obstruction would mask the presence of the subaortic membrane on transthoracic echocardiography and cause a false diagnosis. We report a patient with subaortic stenosis due to flail subaortic membrane misdiagnosed as obstructive hypertrophic cardiomyopathy on transthoracic echocardiography, identified on transesophageal echocardiography and cardiac catheterization.