Subclavian Steal Syndrome : Causes, Risk Factors, Symptoms, Treatment

Arteries and blood vessels play the role of carrying blood from the heart to other parts of the body. Antegrade refers to the flow of blood away from the heart while retrograde is the flow of blood toward the heart.

Subclavian steal syndrome is characterized by an abnormal flow of blood in the arteries. It affects the artery that supplies blood to the neck and head or the arteries supplying blood to the arms.

Subclavian steal syndrome involves the retrograde flow of blood in the vertebral arteries, which means that some amount of blood will be moving away from the neck and head.

According to a report, subclavian steal syndrome affects 0.6% to 6.4% of the general population.⁽¹⁾

Subclavian steal syndrome may vary in severity. It is classified according to the extent to which it disrupts the blood flow.

• Grade 1 (Pre-subclavian steal syndrome): It describes reduced antegrade blood flow in the affected arteries.
• Grade 2 (Intermittent or partial subclavian steal syndrome): A mixture of antegrade and retrograde blood flow in the affected arteries.
• Grade 3 (Permanent or advanced subclavian steal syndrome): It describes the permanent retrograde blood flow in the affected artery.

Arteries play the role of carrying oxygenated blood to all the parts of the body. A person has 2 subclavian arteries, each of which sends blood to a different side of the body. The subclavian artery sends blood to the chest, shoulder, arm, and head.

Subclavian steal syndrome occurs when the heart has difficulty pumping blood through the subclavian artery. This may lead to some degree of retrograde blood flow within the artery and arteries that branch from it.

The most common risk factor for subclavian steal syndrome is atherosclerosis, a condition in which a person’s arteries become blocked or narrow due to the deposition of plaques.⁽³⁾

The plaque build-up may make it difficult for the heart to pump oxygenated blood through the subclavian artery. This may increase the risk of subclavian steal syndrome.

Other risk factors for subclavian steal syndrome include:

• Large artery vasculitis
• Thoracic outlet syndrome
• Narrowing of blood vessels following surgical treatment of certain heart conditions
• Congenital heart irregularities
• Having an extra rib
• Takayasu’s arteritis, an inflammatory condition affecting large blood vessels

Mostly, people with subclavian steal syndrome do not experience any symptoms. If the symptoms develop, they might vary according to the arteries it affected.

Subclavian steal syndrome of the vertebral artery may cause neurological symptoms following certain head movements or upper body exercises. These symptoms occur because the brain and spinal cord are not receiving enough blood to function properly.

According to a 2020 article the common neurological symptoms include:

• Tinnitus
• Dizziness
• Vertigo
• Hearing loss
• Blurred vision
• Fainting
• Loss of muscle coordination

If subclavian steal syndrome affects the arteries carrying blood to the arm, the person may experience symptoms in the affected arm following exercise as the arm might not be receiving enough blood.

The symptoms include:

• Numbness
• Pain
• Tingling and pricking sensations

A study done in 2010 suggested people with subclavian steal syndrome have an increased risk of mortality when compared with the general population.⁽²⁾

As people with subclavian syndrome do not often experience any symptoms, they may benefit from regular health monitoring.

A study done in 2014 found that those suffering from mild symptoms of subclavian steal syndrome observed an improvement in their symptoms without medical intervention.⁽³⁾ However, someone experiencing severe symptoms might need treatment, depending on the symptoms.

People with atherosclerosis and other cardiovascular conditions can find an improvement in symptoms with lifestyle changes, which may include:

• Quitting smoking
• Managing stress
• Following a healthful diet
• Regular physical activity
• Maintaining moderate weight

Sometimes lifestyle changes may not be enough to address the symptoms of subclavian steal syndrome as sometimes the cause may be atherosclerosis.

If a person has atherosclerosis statin may be needed to control cholesterol levels and prevent plaque formation. Additional medication may be needed to control inflammation and blood pressure and prevent the formation of blood clots.

Some people may need surgery to remove the blockage or address the narrowing of the subclavian artery.

The outlook for a person with subclavian steal syndrome depends on the underlying cause and whether the condition is treatable or manageable. In some people, it may improve with medical intervention. As the condition is often symptomless, people who are at its risk should undergo regular health monitoring.