Illustration based on 3D computed tomography (CT) scans of a bicuspid aortic valve (green, centre) showing calcification. This is a heart abnormality present from birth in which the aortic valve only has 2 flaps instead of the usual 3. This can cause health problems such as reduced blood flow from the heart to the body (aortic stenosis) and blood to leak backwards into the heart (aortic regurgitation). The mitral valve is seen in the foreground (green).