During an angiogram procedure the patient is positioned lying down on his or her back on a special table in the hospital examination room. An IV line is then inserted into one of the patient's veins and a mild sedative may be given to help the patient relax. Patients remain awake during the angiogram so they can listen to the doctors and nurses and follow their instructions as well as be able to report to the medical staff any discomfort or other feelings they may have during the procedure.

Electrodes are placed on the patient's chest to monitor the heart during the procedure. Blood pressure and the amount of oxygen in the patient's blood is also measured during an angiogram. The site where the catheter is to be inserted (usually near the groin or in one arm) is washed and then numbed with a local anesthetic. A small incision is made at the insertion site and a plastic sheath is inserted into an artery or vein. The sheath serves as the entryway for the catheter, which is then threaded to the patient's heart.

Once the catheter is in place, special contrast dye is injected into the catheter. This can cause flushing of the face or a warm sensation throughout the body in many patients. It may also cause some to feel their heart is skipping beats. One reason patients are kept awake during an angiogram is so they can report to the doctor or nurse how they are feeling during the procedure. The dye then moves through the patient's blood vessels, during which an X-ray machine is used to take a rapid series of images (angiograms) which give the doctor a detailed picture of the inside of the heart's blood vessels and allow him or her to identify any blockages or areas of obstruction.

After the procedure the incision is closed with a plug or clamp; in some cases a nurse may use manual pressure to close it off. The patient is observed and monitored in the recovery room, where he or she must rest and lie flat for up to several hours after the angiogram is completed.