They are called congenital because they are present at birth and do not go away by themselves. A normal heart . Right and left are as on the person, not as seen.
Arrows indicate direction of blood flow.
Some CHDs are so mild that they may never be noticed, while others are so severe they result in early death. This is especially true if the defect is such that it produces hypoxia in the heart muscle itself. In general the causes of congenital heart problems are now known to result from defects or mutations in genes. Others are associated with chromosomal abnormalities such as Down's syndrome. Most, though, appear during prenatal develolpment or become problems later in life because of changed heart-muscle behavior that starts with protein changes specified by genes.