Subclavian Steal Syndrome

Definition

Subclavian steal syndrome also referred to as subclavian steal phenomenon is a condition characterized by a reversal flow of the blood in the vertebral artery as a result of stenosis or occlusion in the subclavian artery. The term steal in the disease describes the manner of the blood flow where it flows in retrograde pattern and the blood supply is rather stolen from the circular vertebrobasilar system to supply the upper extremities.

The subclavian artery stemmed from the vertebral arteries and serves to supply the upper extremities with blood. It is a paired artery of the chest located below the clavicle and receives blood from the aortic arch. The left subclavian artery branches off the arch of aorta and supply the left arm of the body with blood. The right subclavian artery stemmed from the brachiocephalic artery and supplies the right arm of the body with blood.

Subclavian steal syndrome is a rare condition and is only recognized as an incidental finding during the sonography procedure of the vertebral system. The prevalence of the disease remains unknown as most of the patient suffering from subclavian steal syndrome does not seek medical attention. The left subclavian artery however is found to be more commonly affected than the right subclavian artery. The anatomical location of the left subclavian artery puts it at greater risk for atherosclerosis which is regarded to be the most common cause of subclavian steal syndrome.

Symptoms

The signs and symptoms of subclavian steal syndrome varied although most patients are asymptomatic that the incidence is only recognized as incidental in diagnostic procedure done for some other medical condition.

Numbness of the arm that extends down to the fingertips is the most frequent symptom of the subclavian steal syndrome. The affected arm may also feel heavier compared to the other arm and may also have stiffness.

The following signs and symptoms may be experienced by patient with subclavian steal syndrome:

• Vertigo or a perception of spinning motion is experienced by almost half of the patients suffering from subclavian steal syndrome
• Presyncope or almost fainting and syncope is reported to be exhibited in more than 10% of patients with the syndrome
• Loss of visual which may be from unilateral visual field loss to bilateral visual field loss or total blindness may also occur
• Tingling sensation or numbness in the face
• Transient hemiparesis may also be experienced
• Diplopia or double vision occurs in about 20% of subclavian steal syndrome patient
• The affected arm has a decreased blood pressure of about less than 20mm Hg compared to the unaffected arm
• Problems with memory which tend to be severe
• Blotchy patches of reddish to whitish discoloration in the hands may also occur
• The pulse may be weak or may be absent
• Arm claudication may also occur although this seldom happens and is due to the perfusion of the collateral vessels

The symptoms of subclavian steal syndrome may also be difficult to recognize as it share the same signs and symptoms of other syndromes that are vascular caused.

Causes

Subclavian steal syndrome occurs when there is the presence of an occlusion or narrowing in the subclavian artery. The redundancy in the circulation in the brain and the retrograde flow of the blood as a consequence of the occlusion and narrowing in the subclavian artery resulted to the syndrome.

The blood is being drawn off from the brain, neck and shoulder via the collateral vessels to supply sufficiently the increased demand for oxygen of the upper extremities thereby leading to a reversal flow of blood.

Atherosclerosis is regarded as the most common cause of subclavian steal syndrome. The disease is defined as the narrowing and hardening of the arteries as a result of plaque buildup around the arterial wall. The anatomical location of the left subclavian artery puts it at risk for atherosclerosis that subclavian steal syndrome on the left side of the body is more common than on the right side of the body.

Takayasu disease is a form of Arteriopathies believed to cause subclavian steal syndrome. This disease is characterized by a chronic inflammation of the aorta and the large blood vessels that allocate the blood from the heart. This disease however is considered to be the least common cause of subclavian steal syndrome.

Blalock Taussig shunt is a surgical procedure indicated to increase the blood flow to the lungs. The procedure involves placing a tube between the subclavian artery and the lung artery. Subclavian steal syndrome is highly potential as the subclavian artery is being sacrificed to deliver the aim of the surgical procedure.

Other causes of subclavian steal syndrome include the following:

• Thoracic aortic dissection
• Interrupted aortic arch
• Preductal aortic coarctation in congenital

Risk factors are also considered to increase the incidence of subclavian steal syndrome and such risk factors may include the following:

• Cigarette smoking
• Familial vascular disease
• Hyperlipidemia
• Diabetes mellitus
• Hypertension
• Hypercholesterolemia
• Hyperhomocysteinemia
• Subclavian artery stenosis

Diagnosis

Diagnosing subclavian steal syndrome initially starts with a physical examination. Routine laboratory tests are also necessary to determine the risk for atherosclerosis which is the predominant cause of subclavian steal syndrome.

Imaging tests are vital in confirming the incidence of subclavian steal syndrome where more of these tests can reveal the characteristic of the blood flow in the artery and vein and can therefore define the existence of subclavian steal syndrome. Imaging tests recommended for diagnosing the syndrome include the following:

Doppler ultrasound is an important test in identifying the subclavian artery. The ultrasound can reveal changes in the blood flow and can therefore show a retrograde blood flow if there is any.

CT angiography can easily identify stenosis of the subclavian artery or occlusion and can also identify the location of arterial lesions.

Magnetic resonance angiography is the alternative to the usual angiography in assessing subclavian steal syndrome. It can easily identify the subclavian artery stenosis or occlusion and can also identify the arterial lesion.

Treatment

The goal of treatment in subclavian steal syndrome is to restore the normal pattern of blood flow or the antegrade flow of the blood. Pharmacological treatment of subclavian steal syndrome on the other hand is not yet known to effectively address the condition.

Surgical therapy is the most recommended in treating subclavian steal syndrome and such surgical therapies include the following:

• Endovascular methods are becoming popular due to the minimal invasiveness approach of the method
• Bypass surgery which includes extrathoracic carotid-subclavian bypass
• Percutaneous transluminal angioplasty