This 3D animation from The Human Atlas explains Angiogram.

The heart is a beating muscle that continually pumps blood to the rest of the body. The coronary arteries supply the heart itself with the necessary oxygen and nutrients it needs to function effectively.

Over time, fatty deposits called plaque can build up inside the arteries, clogging the passages and reducing the flow of blood. If the coronary arteries develop plaque, blood flow to the heart can be compromised.

If a patient develops heart-related symptoms, such as chest pain, dizziness or light-headedness, a coronary angiography may be performed to test for the presence of plaque in the coronary arteries.

During angiography, a small incision is made in the upper thigh in order to gain access to the femoral artery. Next, a guide wire is inserted into the femoral artery and is threaded to the aorta. A catheter is then inserted along the guide wire.

Once the catheter reaches the aorta, a contrast dye is injected. When the dye flows from the aorta to the coronary arteries, an x-ray, or angiogram, is obtained. The image taken during angiography will show if there is any blockage, aneurysms, narrowing, or other abnormalities in the arteries.

Following the angiography, the catheter and guide wire are removed. If treatment is necessary, the physician can recommend appropriate therapy.