Stent in a coronary artery. Coloured 3D computed tomography (CT) scan of a stent (green mesh tube at upper right) that has been implanted in the anterior descending branch of the left coronary artery. The stent has been implanted in an operation known as coronary angioplasty, which uses a catheter to place the stent inside the coronary artery. The stent opens up the artery, improving the previously impaired blood supply to the heart muscle. This can prevent conditions such as angina and heart attacks.