Scientists have yet to determine why transposition of the arteries happens in 0.2 of every 1,000 developing fetuses.

What happens is that two main arteries carrying blood away from the heart are reversed.A normal blood pattern carries blood in a cycle: body-heart-lungs-heart-body.But when transposition happens, the blood pathway is impaired because the two arteries are connecting to the wrong chambers in the heart, according to the American Heart Association.This means that the blood flow cycle is stuck in either: body-heart-body (without being routed to the lungs for oxygen), or lungs-heart-lungs (without delivering oxygen to the body).William Ingles at 10 months had what is called the Mustard procedure to save his life.The surgical procedure was developed in the late 1950s, and creates a tunnel, or baffle, between the atria. The atria are the two chambers of the heart that receive blood from the veins and force it by muscular contraction into the two lower chambers on each side of the heart, which in turn force it into the arteries.The procedure redirects oxygen-rich blood to the right ventricle and aorta and the oxygen-poor blood to the left ventricle and the pulmonary artery, according to the American Heart Association.But people who have had the procedure may have problems in their 20s and 30s.The surgery leaves areas of scar that can cause abnormal heart rhythms. Since the right ventricle remains the heart's main pumping chamber, it can become weakened, resulting in congestive heart failure.About half of patients will develop blockage in the baffles that were created to reroute the blood flow, according to the American Heart Association.