You have 2 carotid arteries in your neck that bring blood from your heart to your brain. The test may also look at the vertebrobasilar artery, which also brings blood to your brain.
Your healthcare provider uses a device called a transducer to make pictures of the arteries. The transducer sends out sound waves that bounce off your blood vessels. The sound waves are too high-pitched for you to hear. The transducer then picks up the bounced sound waves and translates them into pictures.
A duplex scan means that the provider uses 2 transducers. The second one (Doppler) lets your provider hear the sound waves the transducer sends out. He or she can hear how fast blood is flowing through a blood vessel and in which direction it is flowing. No sound or a faint sound may mean that you have a blockage in the flow.
You may need this scan if your healthcare provider thinks you may have:
- A blockage (occlusion) in a carotid artery
- Narrowing (stenosis) in a carotid artery
A blockage may be caused by a buildup of fatty material (plaque), a blood clot (thrombus), or other substances.
Symptoms of blockage may include:
- Temporary blindness in one eye
- Temporary inability to speak or move
These symptoms may be early warning signs of a stroke.
You may also need this scan even if you have no symptoms but your healthcare provider hears an abnormal sound (bruit) in an artery. This abnormal sound may mean that you have a problem with blood flow in the artery.
Here are other reasons you may have this scan:
- To see how well blood is flowing after a procedure done on an artery. This may have been a procedure to open up an artery (angioplasty) or surgery to bypass a blocked artery.
- To see how well blood is flowing before you have major heart surgery. This surgery may be bypass surgery or surgery to fix or replace a heart valve.
- To find where clotted blood has collected (hematoma)
- To find out if an artery wall has split (dissection). This may cause a blockage or weaken the artery wall.
Your healthcare provider may have other reasons to recommend a carotid artery duplex scan.
This scan has no risk from radiation. The transducer usually causes no discomfort when put on your skin.
You may have risks depending on your specific health condition. Be sure to talk with your provider about any concerns you have before the scan.
Certain things can make this scan less accurate. These include:
- Severe obesity
- Irregular heart rhythms (arrhythmias)
- Heart disease
- Your healthcare provider will explain the procedure to you. Ask him or her any questions you have about the procedure.
- You may be asked to sign a consent form that gives permission to do the test. Read the form carefully and ask questions if anything is not clear.
- You do not need to stop eating or drinking before the test. You also will not need medicine to help you relax (sedation).
- If you smoke, you may need to stop for at least 2 hours before the test. Smoking causes blood vessels to narrow. You may also be asked to not drink or eat any foods with caffeine for about 2 hours before the test.
- Follow any other instructions your provider gives you to get ready.
You may have this scan as an outpatient or as part of your stay in a hospital. The way the test is done may vary depending on your condition and your healthcare provider's practices.
Generally, a carotid artery duplex scan follows this process:
- You will be asked to remove any clothing, jewelry, or other objects that may get in the way of the scan.
- You will be given a gown to wear.
- You will lie on an exam table with your neck slightly bent backward.
- The technologist will put a clear gel on the skin over the area where the carotid arteries are.
- The Doppler transducer will be pressed against the skin and moved around over the area of the artery being looked at.
- When blood flow is detected, you will hear a "whoosh, whoosh" sound. The probe will be moved around to look at blood flow in different areas of the artery. Both sides of your neck will be looked at.
- Once the test is done, the technologist will wipe off the gel.
The carotid artery duplex scan is not painful. But you may have some discomfort from lying still during the test. The technologist will use all possible comfort measures and finish the procedure as quickly as possible to minimize any discomfort.
You do not need any special care after a carotid artery duplex scan. You may go back to your usual diet and activities unless your doctor tells you otherwise.
Your healthcare provider may give you other instructions, depending on your situation.
Before you agree to the test or the procedure make sure you know:
- The name of the test or procedure
- The reason you are having the test or procedure
- What results to expect and what they mean
- The risks and benefits of the test or procedure
- What the possible side effects or complications are
- When and where you are to have the test or procedure
- Who will do the test or procedure and what that person’s qualifications are
- What would happen if you did not have the test or procedure
- Any alternative tests or procedures to think about
- When and how will you get the results
- Who to call after the test or procedure if you have questions or problems
- How much will you have to pay for the test or procedure
January 16, 2018
Brott, TG. Guidelines on the Management of Patients with Extracranial Carotic and Vertebral Artery Disease, Journal of the American College of Cardiology, 2011 (57);8, pp.e16-e94, Evaluation of Carotid Artery Stenosis, Up To Date
Mancini, Mary, MD,Taylor, Wanda, RN, PhD