July 8, 2014
News Review From Harvard Medical School -- Carotid Ultrasound Not Recommended for All
Most adults don't need to be tested for narrowing of the arteries leading to the brain, an expert group says. The new statement is a final guideline from the U.S. Preventive Services Task Force. This expert group provides advice on preventive care to doctors and the government. The new statement focused on narrowing of the carotid arteries. Narrowed arteries can increase the risk of stroke. Ultrasound can detect these deposits. But the task force concluded that adults with only average risk and no symptoms should not routinely get this test. The test sometimes leads to a "false positive" result. This means that it shows a condition that the person does not really have. But the initial test results often lead to more testing and even surgery. These further steps may cause stroke, heart attack or even death. These potential harms outweigh the potential good of having everyone get a carotid ultrasound test, the task force said. The advice does not apply to people who have a history of stroke or mini-stroke or current symptoms of a stroke. The journal Annals of Internal Medicine published the advice online. HealthDay News wrote about it July 7.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
A narrowed carotid artery means you are at increased risk of stroke. Doctors call it carotid artery stenosis. The carotid arteries are the blood vessels in the neck that supply oxygen-rich blood to the brain.
To reduce the risk of stroke, you'd think it would always be helpful to find a narrowed carotid artery. Once found, it could be opened with surgery. That's the reason that a new report looks at this question: Should all adults have a screening test to look for carotid artery stenosis, even if they feel fine?
The last time the U.S. Preventive Services Task Force formally addressed this question, the answer was no. That was in 2007.
The task force recruits experts with different specialties. This reduces the risk of bias, which can happen when just one specialty group issues guidelines. This time, the expert panel once again recommended against routine screening. The updated advice was posted for public comment earlier this year. Now, the advice is official.
The test used most often to look for carotid artery stenosis is an ultrasound. The test itself is safe and painless.
A doctor or technician puts a wand on each side of the neck. It sends out radio waves to see if there is any narrowing of the carotid artery. There is no radiation. Based on the images, the doctor can estimate the amount of narrowing.
But the test is not "harmless." The ultrasound pictures may suggest a greater narrowing than actually exists. This means more testing and potentially surgery.
The task force provided these reasons for recommending against screening for all adults:
- Only a small number of strokes are directly related to a carotid artery narrowing of 70% or greater. (Doctors consider surgery to open the artery if it is narrowed 70% or more.)
- Less than 1% of the general population has carotid artery stenosis of 70% or greater.
- High blood pressure, high cholesterol, atrial fibrillation (an irregular heartbeat) and diabetes pose a greater risk of stroke than a narrowed carotid artery.
- For those without symptoms, surgery provides only a small improvement in stroke risk compared with just taking medicine.
- The procedure to open the artery carries a risk of stroke, heart attack and death during and right after the surgery.
What Changes Can I Make Now?
The task force advice applies only to routine screening for carotid artery stenosis. An ultrasound of the neck remains an important test for anyone with symptoms that suggest a stroke, even if those symptoms last only a few minutes. In these cases, surgery to open the artery may be needed.
Your doctor may have ordered an ultrasound of your neck arteries for some other reason besides symptoms. Here are some possible reasons:
- Your doctor listens with a stethoscope to your neck and hears a whooshing sound called a bruit. This sound is almost always produced by a narrowed artery.
- You have had a heart attack or have known coronary artery disease or other artery disease.
- You have factors that increase your risk of stroke, such as:
- A family history of heart attack or stroke before age 55 for a man or 60 for a woman
- High blood pressure
- High LDL ("bad cholesterol"), especially if HDL ("good cholesterol") is low
If you have had an ultrasound that shows a narrowed carotid artery, it does not mean you need surgery to open the artery. The narrowing is caused by fatty deposits inside the carotid artery. And it's also happening in a lot of your other arteries as well. This includes the coronary arteries that feed oxygen and nutrients to the heart.
Take action. You can reduce these fatty deposits and prevent new ones. Here's how:
- Don't smoke.
- Stick to a heart-healthy diet, such as a Mediterranean-style diet.
- Maintain a healthy weight to help prevent diabetes.
- Stay physically active and exercise regularly.
- Keep your blood pressure under control.
- Lower your LDL cholesterol, with medicine if necessary. The best medicine is a statin drug.
Low-dose aspirin can help prevent strokes and heart attacks in people with carotid artery stenosis. Ask your doctor if that's the right treatment for you.
If you have atrial fibrillation, you are likely to form blood clots inside your heart. These can break away, travel to the brain and cause a stroke. Your doctor will likely recommend medicine to help prevent blood clots from forming.
What Can I Expect Looking to the Future?
Surgery to open a carotid artery is being performed much less often today than it was 10 to 20 years ago. But for people with a minor stroke or temporary stroke symptoms, surgery may be the best option.
Carotid artery surgery is safer now than ever before. It is safest when your surgeon and the hospital have a lot of experience doing the procedure. If you need this procedure, ask your surgeon how many he or she has done. Better outcomes are linked with a higher number of carotid surgeries performed.
There are no specific guidelines as to the exact number to use. I suggest at least 10 a year, or more than 50 in the last 5 years.