When the coronary arteries become too narrow, cardiologists may perform an angiogram , a test that involves passing a catheter from a large artery in the leg or arm into the heart's coronary arteries. Dye is injected to see how narrow the artery is. If the coronary artery is too narrow, a balloon in the catheter is inflated to dilate the narrowed artery. This is called angioplasty . Arteries in about a third of the patients who have undergone this procedure will become narrow again. To fortify the vessel, a metal device called a stent may be placed inside the narrowed portion of a blood vessel, like a small pipe, to allow blood to flow through them.
The surface of the stent may interact with blood, causing it to clot, which could obstruct blood flow to the heart muscle and cause a heart attack. Most clots are caused by platelets , cells on the blood that help blood clot (see JAMA Patient Page, October 10, 2012). Drugs that impede platelets from forming clots, like aspirin, are given to patients to reduce the risk of clots forming in the stents. Other drugs used for this purpose are prasugrel, ticagrelor, clopidogrel, and ticlopidine. If the stent is uncoated, then some medication to reduce platelet action is necessary throughout the patient's life. Some stents have coatings that slowly release medications to prevent blood clotting. These are called drug-eluting stents, and patients with them only need to take platelet-inhibiting medications for a short while after the stent is placed.