What is it called when the left artery of your child's heart goes up and over instead of down like normal?

Not clear: There are several of the left arteries leaving the child's heart: main one - aorta, which goes from the left ventricle and supplies the brain and the whole body with the oxygenated blood, left coronary arteries, which give the blood supply to the heart (left anterior descending, left circumflex, left marginal).

Abnormal artery: This can be called anamolous origin of coronary artery. If this artery is not in danger from compression from pulmonary arteries than this is a benign variation and no need to worry. Discuss this with your child's cardiologist.