Alan B. Sanderson, MD
DESCRIPTION 
- Subclavian steal syndrome (SSS) refers to the condition where stenosis of the subclavian artery proximal to the origin of the vertebral artery causes diminished blood flow to the distal subclavian artery, and blood flow in the vertebral artery flows in a retrograde fashion in order to supply the distal subclavian artery. Thus, the blood supply to the ipsilateral arm is “stolen” from the posterior cerebrovascular circulation, which then relies on the contralateral vertebral artery. The development is usually chronic.
- SSS was first recognized by conventional angiography in the 1960s. Noninvasive imaging has shown that SSS is much more common than was initially thought, and is usually asymptomatic.
- Most symptoms can be ascribed to ischemia of the posterior cerebrovascular territory. Arm claudication is less common. A related phenomenon, called “coronary-subclavian steal,” involves myocardial ischemia after using the internal mammary artery in coronary artery bypass surgery.
- Systems affected: Central nervous system, Cardiovascular system
- Synonyms: The term “subclavian steal phenomenon” refers to asymptomatic SSS. Some authors reserve the term “subclavian steal syndrome” for symptomatic cases only.
EPIDEMIOLOGY
Incidence
No specific data are available.
Prevalence
- Estimates range from 0.4–6.4%.
- A 2010 study found subclavian steal in 5.4% (429/7,881) of patients referred for carotid duplex ultrasound to investigate cerebrovascular disease. Only 8.9% (38/429) of these were symptomatic (0.5% of total subjects) (1).
- Age/gender: Most patients are male, aged >50 years old.
RISK FACTORS
Genetics
No genetic syndrome is identified.
GENERAL PREVENTION
Smoking cessation, medical management of hypertension, dyslipidemia, and diabetes
PATHOPHYSIOLOGY
- When the blood pressure in the basilar artery is greater than the blood pressure in the distal subclavian artery, then blood flow along the vertebral artery will be in a retrograde direction.
- The left side is involved about 80% of the time. Bilateral SSS is uncommon.
- Subtypes:
- Complete: Flow in the vertebral artery is retrograde throughout the cardiac cycle.
- Partial: Flow in the vertebral artery is anterograde during diastole, retrograde during systole.
ETIOLOGY
- Atherosclerosis is by far the most common cause.
- Takayasu arteritis is a rare cause, classically occurring in females of Asian descent younger than 30 years old. Takayasu arteritis involves proximal subclavian stenosis in up to 85% of patients, and is more likely than atherosclerosis to cause bilateral disease.
COMMONLY ASSOCIATED CONDITIONS
Vascular disease at other sites, including coronary artery disease, carotid stenosis, and peripheral vascular disease.
[Outline]
HISTORY
- Symptoms of vertebrobasilar insufficiency can include dizziness, vertigo, visual changes, loss of consciousness.
- A minority of patients complain of arm claudication.
- Patients with coronary-subclavian steal may complain of cardiac chest pain.
- Symptoms are usually transient, and may accelerate in severity or frequency over months. Exercise of the ipsilateral arm may provoke symptoms.
PHYSICAL EXAM
- Vital signs: A blood pressure differential (PD) between the two arms >20 mm Hg is strongly associated with SSS. SSS was found in 77% of patients with PD of 20–30 mm Hg, 90% of patients with PD of 30–40 mm Hg, and 100% of patients with PD >40 mm Hg. As PD increases, complete SSS becomes more likely. The proportion of symptomatic patients also increases with increasing PD. Bilateral SSS is less likely to have PD >20 mm Hg, but the systolic blood pressure in both arms is usually <100 mm Hg in these patients (1)[C].
- Cardiovascular: Listen for bruits over the heart and great vessels, including the neck vessels. Palpate the radial and/or brachial pulses bilaterally, noting any differences in timing or amplitude between sides.
- Neurologic: Perform a complete screening neurologic examination, paying careful attention to the cranial nerves and visual system. Between episodes the neurologic examination is usually normal.
- Symptoms can sometimes be elicited during examination by having the patient exercise the ipsilateral arm.
DIAGNOSTIC TESTS AND INTERPRETATION
Lab
Initial Lab Tests
There are no specific laboratory tests.
Follow-Up & Special Considerations
Consider checking serum inflammatory markers in patients suspected of having Takayasu arteritis.
Imaging
Initial Approach
Duplex ultrasound is the initial test of choice because it is noninvasive, relatively inexpensive, has few contraindications, and readily visualizes the direction of flow in vessels (1)[C].
Follow-Up & Special Considerations
CT, MRI, or conventional angiography may also be useful in certain cases, especially if intervention is planned (1)[C].
Pathological Findings
Biopsy is not usually performed. Histology usually shows atherosclerosis. Histology of Takayasu arteritis shows inflammation of the vasa vasorum during the acute phase, and fibrosis with destruction of elastic tissue during the chronic phase (4)[C].
DIFFERENTIAL DIAGNOSIS
- Other causes of neurologic symptoms: Vertebral or basilar artery stenosis, thromboembolic disease, basilar migraine, infectious, inflammatory, or neoplastic disease involving the brainstem, toxic or metabolic conditions such as hypo- or hyperglycemia, syncope, seizure, trauma
- Other causes of arm symptoms: More distal arterial stenosis or occlusion, peripheral neuropathies, including mononeuritis multiplex, entrapment neuropathies, and brachial plexopathies, other causes of thoracic outlet syndrome, asymmetric myopathy
- Other causes of cardiac symptoms: Coronary artery disease, coronary vasospasm, non-cardiac chest pain
[Outline]
MEDICATION
First Line
- Because SSS is rare, there are no randomized trials to guide management.
- Antiplatelet agents, such as aspirin 81 mg daily (1,2)[C].
- Medical management of underlying risk factors for vascular disease, including blood pressure, diabetes, and dyslipidemia (1,2)[C].
- Treatment of Takayasu arteritis where applicable, usually with corticosteroids (4)[C].
Second Line
Other antiplatelet agents, such as clopidogrel 75 mg daily.
ADDITIONAL TREATMENT
General Measures
- Smoking cessation
- Patients may be counseled to avoid exercise of the affected arm, and to avoid other inciting factors such as neck positions, etc.
Issues for Referral
Patients should be followed by a vascular surgeon. There are no data to guide the timing or interval of visits (1,2)[C].
SURGERY/OTHER PROCEDURES
Endovascular approaches have been used since the 1990s. A 2009 paper reported 104 consecutive patients treated with either balloon angioplasty alone or angioplasty with stenting, with an overall technical success rate of 96% and sustained 1-year primary patency of 88%. Complication rates are low, and the procedure is less invasive, so many recommend this approach as first-line therapy (2)[B].
- Traditional vascular surgery approaches such as carotid-subclavian bypass show superior 5-year patency rates in the range of 95%, but complication rates between 12 and 29% (2)[B].
IN-PATIENT CONSIDERATIONS
Initial Stabilization
- There are no specific data to guide management.
- Assure adequate blood pressure
- Control blood glucose
- Prompt diagnosis to rule out other conditions
Admission Criteria
There are no specific data to guide management. It is prudent to admit patients who may be candidates for intervention due to severity of symptoms, or who need a number of diagnostic tests to rule out other potential conditions.
IV Fluids
If indicated for hypotension in the setting of active symptoms. There is no preference for one type of IV hydration.
Nursing
- Assure glucose control in patients with diabetes.
- Manage accurate administration of medications.
- Provide patient education on SSS and comorbid conditions.
Discharge Criteria
There are no specific data to guide management. Clinicians should use their best judgment to discharge patients safely after an appropriately thorough workup, and after watching for and managing any complications of therapy.
[Outline]
FOLLOW-UP RECOMMENDATIONS
- Patients should be followed by a vascular surgeon.
- Primary care doctors or medical specialists should provide treatment for underlying medical risk factors.
- Neurologists may be involved to follow the course of neurologic symptoms.
PATIENT MONITORING
- Most patients can be managed in the outpatient setting, but may be admitted for initial diagnosis or for procedures.
- There is no consensus on surveillance imaging after diagnosis or after procedural interventions.
- Patients who undergo endovascular procedures may require additional procedures to repeat angioplasty or stenting in the case of restenosis (1,2,3)[C].
DIET
- Diets shown to be helpful in other atherosclerotic vascular diseases are likely to be helpful in vertebrobasilar insufficiency, but there are no research studies addressing this topic.
- Diabetic diet if applicable.
PATIENT EDUCATION
- Patients should be educated regarding the cause of their symptoms and treatment options.
- Patients should be informed of underlying risk factors for SSS and counseled regarding smoking cessation and compliance with medical therapies for hypertension, dyslipidemia, and diabetes.
- Patients should know what symptoms should prompt them to seek medical care.
PROGNOSIS
The overall prognosis is not known. Whether symptomatic patients improve with medical therapy alone or whether they eventually require procedural intervention is not known.
COMPLICATIONS
Coronary-subclavian steal can occur in patients who have coronary artery bypass surgery using the internal mammary artery.
[Outline]
ICD9
435.2 Subclavian steal syndrome