Coarctation of the aorta is a congenital heart disorder where the aorta is abnormally narrow. This defect forces the left ventricle to work harder, which can lead to heart failure.In a healthy heart, the left atrium fills with oxygenated blood from the lungs, and then passes it to the left ventricle. Pumped by the left ventricle, the blood then travels through the aorta to the rest of the body. First, several arteries branch off the aorta to take blood to the head and arms. Then the aorta takes blood toward the legs and abdomen. Coarctation generally occurs after the aorta has branched to bring blood to the upper body, but before it has brought the blood toward the lower body. Some of the blocked blood thus is rerouted towards the upper body. This leads to high blood pressure in the arms and head, and low blood pressure in the legs and abdomen.