Coloured 3D computed tomography (CT) scan of the heart of a child with coarctation of the aorta, the body's main artery (red). This is a congenital (present at birth) defect, where part of the aorta is narrowed (at upper right). This narrowing causes the heart to need to beat harder to pump blood around the body. Mild cases may not be diagnosed until adulthood, but severe cases can lead to heart failure and death if not treated. Treatment is with surgery to either widen or replace the affected area.