An anomalous left coronary artery from the pulmonary artery is a problem that occurs when the baby's heart is developing early in the pregnancy. The developing blood vessels in the heart do not connect correctly.
In the normal heart, the left coronary artery starts in the aorta. The aorta is the major blood vessel that takes oxygen-rich blood from the heart to the rest of the body.
In children with ALCAPA, the left coronary artery starts at the pulmonary artery. The pulmonary artery is the major blood vessel that takes oxygen-poor blood from the heart to the lungs.
When this defect occurs, blood that is lacking in oxygen is carried to the left side of the heart. Therefore, the heart does not get enough oxygen. When the heart muscle is deprived of oxygen, the tissue begins to die. This condition leads to a heart attack in the baby.
A condition known as "coronary steal" further damages the heart in babies with ALCAPA. The low blood pressure in the pulmonary artery causes blood from the abnormal left coronary artery to flow toward the pulmonary artery instead of toward the heart. This results in less blood and oxygen to the heart. This problem will also lead to a heart attack in a baby. Coronary steal develops over time in babies with ALCAPA if the condition is not treated early.