Transposition of the great arteries associated with a double left ventricular outflow tract.

A case is described in which, at semilunar valve level, the aorta and pulmonary artery arose from inappropriate ventricles. Despite this, the outflow tracts to both vessels originated from the left ventricle. Embryologically, it is speculated that this anomaly is the result of normal rotation of the proximal conus, without concomitant truncal inversion, and excessive leftward shift of the proximal conus and conal septum or anterior and rightward deviation of the anterior segment of the ventricular septum. Surgical repair using a double conduit between the right ventricle and pulmonary artery and left ventricle and aorta, respectively, was unsuccessful.