Congenital heart disease refers to a form of heart problem that starts before birth (congenital). Congenital heart disease includes a large number of conditions. The formation of the heart before birth is very complex and is sometimes abnormal. For example, if a part of the main artery that comes from the heart is narrowed, that is called coarctation of the aorta. There may be holes inside the heart which keep the blood from flowing normally inside the heart. Other congenital heart problems are caused by abnormal heart valves. In some cases, congenital heart problems are discovered at birth. Other times the problems may not be detected until the person is an adult