Discrete Sub Aortic Membrane: the Role of Trans Esophageal Echocardiography

Discrete subaortic membrane is a rare cause of left ventricular outflow tract obstruction. The Mmode and two-dimensional transthoracic echocardiographic features of discrete subaortic membrane have been described previously. In this study transesophageal e.chocardiography (TEE) have been performed in 8 patients. previously diagnosed by transthoracic echocardiography to have discrete subaortic membrane. The study showed that TEE is far superior to transthoracic echocardiography in clearly showing the discrete membrane in full length with clear points of insertion. Moreover. the distance of the membrane from the aortic valve as well as the thickness of the membrane can be measured more accurately. Aortic regurgitation, a common complication of discrete subaortic membrane, was present in 7 patients. The severity of aortic regurgitation correlated inversely with the distance of subaortic membrane from the aortic valve. Although it was generally accepted that discrete sub aortic membrane is a congenital anomaly, some reports raised the question of whether discrete subaortic membrane is a congenital or an acquired lesion. There are some suggestions that the subaortic membrane may be derived from endocardial proliferation with fibrosis into the left ventricular outflow tract stimulated by turbulent blood flow through ventricular septal defects. This hypothesis may be supported by our findings in one patient who has a small ventricular septal defect and a very short membrane extending only a few mm from the interventricular septum. Further follow-up by TEE may show the progressive nature of this membrane.