What Is a Carotid Doppler Test?

The carotid Doppler test, or carotid ultrasound, is a non-invasive test that uses sound waves to detect narrowing of your arteries or potential blockages caused by plaque. It helps your healthcare provider determine if you are at risk of having a stroke and if you need treatment to prevent it.

This article explains the purpose of a carotid ultrasound, what to expect during the procedure, and how the results are used.

What Does a Carotid Doppler Look For?

You have two large carotid arteries in your neck that supply blood to the brain. A Doppler, or ultrasound, uses sound wave imaging technology to monitor these arteries.

A physician prescribes a carotid ultrasound for a variety of reasons, including if:

• You have an increased risk of having a stroke.
• You have a blockage, known as an occlusion, from plaque, a blood clot, or something else.
• Your carotid artery is narrowing, known as stenosis.
• Your healthcare provider hears an abnormal sound in your artery.
• You had a TIA (transient ischemic attack).
• You have a stent placement in your carotid artery that needs to be evaluated.
• You a have a condition such as diabetes, high blood pressure, or high cholesterol.
• You are preparing for coronary artery bypass surgery.
• You have a family history of stroke or heart disease.
• You have been diagnosed with a hematoma.

How to Prepare for the Test

Wear something loose and comfortable that does not cover your neck. Avoid necklaces and/or earrings; your healthcare provider will likely ask you to remove them.

Your healthcare provider should explain the proper protocol to you and should be able to answer any questions you may have. There are few restrictions or instructions on preparing for a carotid Doppler test.

Before your test, you may need to:

• Sign a consent form.
• Stop smoking for at least two hours before your appointment.
• Stop drinking or eating anything containing caffeine two hours before your appointment.

What to Expect During the Test

For most people, a carotid ultrasound takes an average of 15 to 30 minutes. The test is done in a special room with the Doppler machine and a table for you to lie on.

You can expect your healthcare provider to follow the five steps listed below, but what actually happens may vary depending on your condition, so follow their instructions.

1. Remove any clothing or jewelry that blocks your neck area.
2. Lay on a table with your neck bent back slightly.
3. The ultrasound technician will apply a lubricating, jelly-like substance to both sides of your neck, where the carotid arteries are.
4. The Doppler or ultrasound wand is moved back and forth over the neck to detect blood flow.
5. You will hear a "whooshing" sound from the machine.

After the images are captured, you will be given towels to help wipe off the lubricant. You can then get dressed and leave the testing room.

After the Test

Once the test is complete, you are free to resume normal activities with no restrictions, unless your healthcare provider recommends otherwise. The results should be available within a few days at most.

After your test, here's what happens next:

1. An ultrasound technician records the completed test on a videotape. 
2. A diagnostic radiologist reviews the tape to measure blood flow and determine the amount and location of any narrowing of the carotid arteries.
3. The radiologist then sends a report to your physician. 
4. The radiologist will review the written report.
5. The results of your test, along with other factors determined by your individual condition, guide further treatment recommendations.

Interpreting the Results

Your healthcare provider will be given a report within days of the test. These results will be shared with you in person or during a telehealth appointment.

A Doppler scan measures the flow of blood. A normal result will typically show the blood moving at a rate of 30 to 40 centimeters per second. However, the normal range varies from person to person. Normal test results mean that there is no narrowing of the arteries or that there is no significant blockage or problem.

Follow-Up Testing

Once your healthcare provider shares your results, they may also recommend that the test be repeated in the near future. Another Doppler carotid test may be necessary to get more details because there was an issue with the first scan. Repeat scans may also be used to compare earlier and later readings to see if treatment is working.

Depending on your Doppler results, your healthcare provider may also recommend other tests. These include:

• Computed tomography (CT) angiogram scan: A CT scan is a noninvasive type of X-ray that creates a 3D image of the blood vessels in your body. Using dye injected into your vein, the image can show details of your carotid arteries.
• Magnetic resonance imaging (MRI): An MRI uses a strong magnetic field and radio waves to produce two- or three-dimensional images of your blood vessels.
  

These tests may not be covered by insurance in some instances, which is one of the reasons they’re not the first choice of healthcare providers. However, they can offer important details when the results of a carotid doppler are unclear.

Evidence of Stroke Risk

If the Doppler shows you're at risk for having a stroke, your healthcare provider may recommend lifestyle changes to lower the risk.

They may suggest changing your diet to include foods low in saturated fats, trans fats, and cholesterol as well as those high in fiber and low in sodium.

Other lifestyle changes may include:

• Maintaining a healthy weight
• Getting regular physical activity
• Avoiding smoking and secondhand smoke
• Limiting alcohol consumption

Your healthcare provider may also adjust your medication or prescribe additional medications to help lower your risk of stroke. These may include:

• Medications such as Bayer (aspirin) or Plavix (clopidogrel) to prevent blood clots
• Statins such as Lipitor (atorvastatin) to lower your cholesterol
• Antihypertensives such as ACE inhibitors or calcium channel blockers to lower your blood pressure
  

If you have severe plaque buildup, your healthcare provider may recommend a carotid endarterectomy. This is a surgical procedure to remove plaque from the carotid artery. Severe blockages can also be treated with angioplasty, a procedure that uses a balloon to create a wider opening in a narrow or blocked artery.

Summary

A Doppler carotid test is a non-invasive way to check your cardiovascular health. The ultrasound is safe and easy and offers images of soft tissue that cannot be seen on an X-ray. With the information provided, your healthcare provider can see if you need treatment for a blockage, which can go far to prevent a stroke.