The coronary arteries supply blood to the heart muscles; if they become narrowed or blocked by accumulations of plaque (coronary artery disease), this can impair the functioning of the heart. To determine whether, where, and to what extent an artery is blocked, an interventional cardiologist may perform a coronary angiogram. This procedure provides an X-ray picture of the artery. A thin, flexible tube called a catheter is inserted in the patient’s arm, leg or neck and guided through the blood vessels to the coronary arteries, where it is used to inject a special dye into the artery that allows the image to be taken. A coronary angiogram is minimally invasive and involves little to no pain.