What Are Its Effects?

Unlike the other form of Transposition (Transposition of the Great Arteries: D-Type), the blood flow in this defect is normal. Oxygen-rich blood from the lungs is pumped through the aorta to the body and oxygen-poor blood from the body is pumped through the pulmonary artery to the lungs. Therefore, the abnormal positions of the ventricles and great arteries do not cause problems per se.  However the right ventricle is now the systemic ventricle, and prone to failure over decades.

However, the defects that may be associated with this condition, such as ventricular septal defects, narrowing of the pulmonary artery, defective tricuspid valve, and a defective pacemaker, may cause difficulties.

Perhaps the most serious complication that may arise stems from the abnormal conduction system. (Please see Electrophysiology for a discussion of normal conduction.) Because the conduction pathways differ significantly from the normal arrangement, the beating of the heart may be abnormal. In extreme cases, there may be the development of third degree, or complete, heart block, in which the atrial and ventricular pumping become completely out of synch with a slow overall heart rate.