Coarctation of the aorta is a constriction (narrowing) of a part of the aorta, the main artery carrying "red blood" to the body. This generally occurs close to the region where arteries to the head and neck arise. The constriction obstructs blood flow to the lower parts of the body. It causes blood pressure to increase above the coarctation, resulting in higher blood pressure in the upper part of the body compared with the lower part of the body.

The left side of the heart works hard as it tries to pump blood past the coarctation. This may cause the left ventricle to enlarge. If the coarctation is very severe, an infant's heart may fail, resulting in rapid heart rate, rapid breathing and poor feeding. In less severe narrowing, the child may have no noticeable side effects except increased blood pressure. If the high blood pressure continues, damage results to other blood vessels in the body.

The age when the coarctation is repaired depends on the severity of the constriction and the patient's symptoms. Usually, surgery is needed very early in infancy. Children with coarctation require penicillin (also called SBE prophylaxis) prior to any dental work or surgery on the mouth, bowel, or bladder. This helps prevent the uncommon, but possible, occurrence of bacterial infection affecting the heart near the defect or the heart valves.