Aneurysm of the membranous ventricular septum resulting in pulmonary outflow tract obstruction in congenitally corrected transposition of the great arteries.

Aneurysm of the membranous ventricular septum causing subpulmonic obstruction in patients with corrected transposition is rare but well documented. Higher left-sided (morphologic right) ventricular pressure causes protrusion of the aneurysm into the pulmonary outflow tract of the right-sided morphologic left ventricle, causing obstruction related to lack of conus and proximity of the aneurysm to subpulmonary region. Echo Doppler studies and angiography are useful in making a correct diagnosis. Surgical resection of the aneurysm along with closure of the ventricular septal defect is the treatment of choice. The prognosis is likely to be excellent.