A narrowing of the AORTA in the vicinity of the insertion of the DUCTUS ARTERIOSUS. It is a congenital abnormality sometimes not discovered until well into childhood or adolescence. The diagnosis is initially suspected by discovering a major difference between the pulses and blood pressure in the arms and that of the legs. Confirmation is by ultrasound. If untreated it leads to hypertension and heart failure, which can be prevented by surgical correction of the anomaly in infancy. Paediatricians screen for coarctation by feeling for femoral pulses, which are absent or weak in this condition.