A coronary angiogram is a special X-ray test. It shows whether your coronary arteries are narrowed or blocked. The coronary arteries supply your heart muscle with blood. They can become clogged from a buildup of cholesterol, cells or other substances (plaque). This can reduce the blood flow to your heart.
If plaque in a heart artery breaks, a blood clot forms. The clot further blocks the blood flow through the narrowed artery. If the blood flow is completely blocked to part of the heart muscle, it can result in a heart attack. An angiogram can help show where and the percentage your arteries are blocked. This information helps your health care team choose what treatment you need.