In transposition of the great arteries, the two major arteries leaving the heart are connected to the wrong ventricles, the two lower chambers of the heart. The result is that blood containing oxygen from the lungs is pumped back into the lungs, while blood that lacks oxygen, which is necessary to nourish the body, is pumped throughout the body.

Permanent treatment requires a surgical procedure to switch the arteries to their proper places. This operation, called an arterial switch operation, is done within the first few weeks of life. It is an open-heart procedure that requires a temporary stopping of the baby's heart while a heart-lung machine handles respiration and blood circulation. Any abnormal holes between the ventricles or atria also are closed.

As part of the procedure, the coronary arteries - the arteries that supply blood to the heart - have to be taken off their normal position on the aorta and transplanted into the new "aorta" that now carries oxygenated blood from the left ventricle around the body. Rarely, this may be lead to problems that require further procedures.