The procedure will begin with the physician inserting an intravenous (IV) line into the patient’s arm. The IV allows the physician to give the patient a sedative and other necessary fluids or medications during the procedure.

Most patients will receive a local anesthetic and remain awake for the procedure. However, some patients, especially young children, may be given a general anesthetic and sleep through the procedure. Small devices (electrodes) will be taped to the patient’s body, which allow the physician to monitor heart rate. A small device (pulse oximeter) may be clipped to the patient’s finger to monitor the blood oxygen level during the procedure. The patient’s head will be placed into a positioning device to keep it still during the test.

The catheter can be inserted in the femoral artery of the groin (most common), the carotid artery in the neck (rarely), or the brachial artery of the arm. If the carotid artery is used, sandbags or a towel will be placed under the patient's shoulder to hyperextend the head and neck. If the brachial artery is used, a blood pressure cuff will be placed on the patient’s arm below the insertion site so the dye released from the catheter will not go down into the arm and hand.

The insertion site is cleaned, shaved and numbed (with a local anesthetic). The physician then inserts a thin catheter (using a special needle and wire) into a blood vessel and feeds it through the artery and up into the head. There may be some minor discomfort during this period, but most patients do not feel the catheter moving through the body.

When the catheter reaches the target area, a dye (contrast medium) is injected through the catheter. This dye allows the physician to clearly see the cerebral arteries on the angiogram. The patient may feel hot and flushed for about 10 seconds as the dye is administered. Allergic reactions to contrast dyes are rare. However, patients should inform the physician or testing technician immediately if they experience any of the following sensations during the procedure:

The dye is easily visible to the physician monitoring the angiogram images, which may be viewed on a television monitor or as a series of still images. A series of x-rays will be taken as the physician views the images. A “shadow” cast by the dye will show blockages or irregularities of the arteries. In the case of diseased arteries, for example, arterial walls may appear to be abnormally narrow or irregularly shaped.

Once the angiograms have been taken, the catheter is removed from the body and pressure is placed on the point of catheter entry. In some cases, a small “plug” will be placed in the puncture site to stop the bleeding. This plug will be normally absorbed by the body over time.

The length of the angiogram procedure will depend on which blood vessels are being targeted. The angiogram procedure may take 15 minutes to an hour, or a total of one to two hours from pre-procedural preparation to the removal of the catheter.