Prosthetic heart valve. 3D CT (computed tomography) scan of a 70-year-old patient's chest. This is a profile view of the left side, with the front of the chest at left and the spine at right. The prosthetic heart valve (white) is seen at centre left, with the heart below it. The stitches used to close the chest are seen at upper left. The heart valves prevent backflow of blood in the heart. If they start to fail, a condition known as incompetence, then the patient may not get enough oxygenated blood. This leads to shortness of breath, chest pain and possibly a heart attack. The replacement valve here is artificial, but some can be from donors or even from other animals, usually a pig.