- Characterized by pulmonary stenosis, ventricular septal defect, overriding of the aorta, and right ventricular hypertrophy.
- The spiral ridges may unequally separate the aorta from the pulmonary trunk, so that the pulmonary trunk is poorly developed.  The aorta is overdeveloped so that it cannot now be connected to the interventricular foramen and it comes to override the interventricular septum and receives blood from both ventricles.

- The two ventricles are in open communication so that the pressure in the right ventricle is as high as that in the left ventricle, and the wall of the right ventricle is hypertrophied.

- The following combination is Fallot's tetralogy: Pulmonary stenosis (narrowed pulmonary trunk), right ventricular hypertrophy, ventricular septum defect, overriding aorta.

- The venous blood entering the aorta causes cyanosis. (blue baby).
- Can surgically form an artificial ductus arteriosus and so increase the pulmonary circulation, increase the pressure in the left ventricle and reduce the amount of blood entering the aorta.

Reference:
1. Anatomy & Physiology Manual. Butler L, Bouncir G, Burnett G. Lancashire & South Cumbria Cardiac Network. 2004.