Because of the displacement of the malaligned outlet septum
into the right ventricle, the aortic root, of necessity,
overrides the muscular ventricular septum. In the setting
of significant subpulmonary obstruction, shunting across
the interventricular communication is predominantly
from right-to-left, which promotes ejection of deoxygenated
blood into the systemic circulation. The chronic volume
load sustained by the overriding aorta is implicated
in the dilation of the aortic root noted in adults with
tetralogy of Fallot [7,8].