Subclavian steal syndrome occurs when blood flow reverses in one of the arteries supplying blood to the neck, head, and arms. The condition is usually caused by a narrowing in one of the arteries and is treatable.

Subclavian steal syndrome is a circulation issue that occurs when blood flow is reversed in one of the arteries supplying blood to the neck, head, and arms. It’s an uncommon condition that usually affects older adults.

Symptoms of subclavian steal syndrome can range from mild to severe. Depending on the location and severity of the arterial blockage, treatment might be limited to the management of cholesterol and blood pressure levels. Or it may require an invasive procedure to improve blood flow in the affected artery.

Subclavian steal syndrome is usually a treatable condition with a low risk of long-term complications.

This article examines the symptoms and causes of subclavian steal syndrome, along with its diagnosis, treatment, and outlook.

Infographic showing reverse blood flow in subclavian steal syndromeShare on Pinterest
Subclavian steal syndrome occurs when blood flows from your brain (rather than from your heart) to your arm. This reverse blood flow is typically caused by a narrowing in one of the arteries. Illustration by Jason Hoffman

The subclavian arteries are located just below the collarbone (clavicle). They supply blood to the vertebral arteries, which carry blood away from the heart to the brain and spine, and to the arteries in both arms.

If you have subclavian steal syndrome, it means blood flows down from your brain (rather than from your heart) to your arm.

The change in blood flow usually occurs when there is a narrowing in one of the arteries (called “stenosis”). This disrupts the heart’s ability to pump blood through that blood vessel. This “backward” blood flow is called retrograde blood flow.

Can subclavian steal syndrome cause a stroke?

Even though a certain type of subclavian steal syndrome means that blood that might otherwise reach the brain is flowing away from the brain, the condition does not appear to raise the risk of stroke.

A 2021 study involving patients diagnosed with acute ischemic stroke suggests that only 2.2 percent of them also had subclavian steal syndrome and that the condition did not contribute to their stroke. Instead, researchers proposed that atherosclerosis — the buildup of plaque within arteries — was a contributing factor to both subclavian steal syndrome and stroke.

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It’s not clear how prevalent subclavian steal syndrome is, though estimates range from 0.6 percent to 6.4 percent of the general population.

Subclavian steal syndrome is usually the result of atherosclerosis, the narrowing of an artery due to the buildup of plaque along artery walls. When normal blood flow becomes blocked or severely restricted, retrograde blood flow may occur in that artery.

Risk factors for subclavian steal syndrome include:

Subclavian steal syndrome can also develop because of a malformed blood vessel. The malformation may be one you’re born with (congenital) or be the result of a medical procedure like angioplasty.

Subclavian steal syndrome symptoms can vary, depending on which arteries are experiencing retrograde flow. For many people, the condition presents no noticeable symptoms.

However, when symptoms present, they can be quite severe and come on suddenly. For example, if one of the arteries supplying blood to the arms is affected, arm pain is more likely to develop from physical exertion.

Other possible subclavian steal syndrome symptoms include:

  • aphasia (difficulty speaking or understanding speech)
  • ataxia (impaired motor control and coordination)
  • dizziness
  • headache
  • fainting (syncope)
  • lightheadness
  • vertigo
  • visual disturbances

Some of these symptoms, including aphasia, headache, and a decrease in motor control, are also among the signs of a stroke, and should therefore be treated as medical emergencies.

Likewise, sudden lightheadedness and arm pain can sometimes indicate a heart attack. These symptoms also should prompt a 911 call or trip to the emergency department.

Diagnosing subclavian steal syndrome starts with a review of your symptoms and medical history, as well as your family’s medical history. Then blood pressure is measured in both arms.

A 2020 American Academy of Ophthalmology report suggests that a difference in blood pressure readings of more than 20 mmHg may indicate subclavian steal syndrome.

Bedside screening using Doppler ultrasound, a noninvasive imaging test that uses sound waves to create images of inside the body, may help detect retrograde blood flow. Other imaging tools that may be used include carotid duplex ultrasonography and magnetic resonance angiography.

If you have subclavian steal syndrome, but you do not have symptoms or your symptoms are mild, you may not need treatment. But because the condition is often a sign that there may be atherosclerosis elsewhere in the body, your doctor may recommend measures to help manage your:

You may also be advised to quit smoking if you smoke and adopt a heart-healthy lifestyle that typically includes:

Balloon angioplasty

When there’s extensive or complete arterial blockage, balloon angioplasty can be a safe and effective means of restoring proper blood flow, according to a 2020 study.

In balloon angioplasty, a catheter fitted with a small, deflated balloon at one end is guided through a blood vessel to the blockage. The balloon is then inflated, pushing aside the plaque in the artery and allowing blood to flow normally again. In some cases, a mesh stent is left in place to keep the artery open after the balloon and catheter are withdrawn.

Your doctor may also prescribe medications like antiplatelet agents and anticoagulants to help lower the risk of blood clots.

Subclavian steal syndrome itself isn’t usually life threatening. It’s manageable, especially with a health-promoting lifestyle and consistent management of cardiovascular disease risk factors. For those reasons, the outook is usually positive for people with subclavian steal syndrome.

Keep in mind that a diagnosis of subclavian steal syndrome may be an indicator that you may be at risk for other, potentially more serious circulation problems.

Subclavian steal syndrome may be a benign condition that causes you few if any problems. But it should be viewed as an indicator to be proactive about your cardiovascular health.

Managing your blood pressure, blood glucose, and cholesterol and keeping up with your scheduled physicals and other medical exams and screenings can help you identify any similar circulation problems early to help prevent more serious complications.