The obstruction to blood flow caused by the coarcation causes high blood pressure in the left ventricle (which pumps blood into the aorta) and the part of the aorta between the heart and the blockage (the aortic arch - AA in diagram).

While the blood pressure in the upper body becomes high, the blood pressure in the lower body is low because of the reduced blood flow through the aorta. If the obstruction in the aorta is severe, infants will develop severe heart failure and low perfusion of the lower body organs after the patent ductus arteriosus (PDA) closes in the first several days after birth. If the problem is not diagnosed promptly, the infant may die.