Ocular symptoms of subclavian steal syndrome

Key Points at a Glance

Key Points of This Disease

• This disease is caused by proximal stenosis or occlusion of the subclavian artery, leading to reversal of blood flow in the ipsilateral vertebral artery and hypoperfusion of the vertebrobasilar system.
• The prevalence is 0.6–6.4%, more common in men over 50 years old, and occurs on the left side in approximately 82% of cases.
• Visual symptoms may include blurred vision, diplopia, visual field defects, and transient monocular vision loss.
• Suspect this disease when the systolic blood pressure difference between both arms is 20 mmHg or more, and confirm the diagnosis with specialized imaging tests.
• Percutaneous transluminal angioplasty with stent placement is currently the first-line treatment, with a reported 5-year patency rate of 83–89%.
• Many cases are asymptomatic due to compensation by extensive collateral circulation.
• As a systemic vascular disease based on arteriosclerosis, comprehensive management of risk factors is important.

1. Ocular symptoms of subclavian steal syndrome

Subclavian steal syndrome (SSS) is a condition in which stenosis or occlusion of the proximal subclavian artery causes reversal of blood flow in the ipsilateral vertebral artery. This leads to hypoperfusion of the vertebrobasilar system, reducing blood flow to the occipital lobe, brainstem, and eyes, resulting in various neurological and ocular symptoms.

In 1960, Contorni reported the first case of angiographic reflux in a patient with absent radial pulse, and in 1961, Fisher coined the term “subclavian steal”.

Epidemiology

• Prevalence: 0.6–6.4%¹⁾. Found in 2–4% of the general population, and more frequent in patients with comorbid cardiovascular disease³⁾
• Patient background: More common in men, with a male-to-female ratio of 2:1, and predominantly occurs in those aged 50 years or older⁶⁾
• Laterality: The left subclavian artery accounts for 82.3% of cases, and bilateral involvement is 13%
• High rate of asymptomatic cases: While approximately 30% of patients with peripheral artery disease have subclavian artery stenosis, only 38.5% of those with a blood pressure difference of 50 mmHg or more exhibit symptoms⁴⁾
• Differential perspective: 17% of extracranial arterial diseases are due to subclavian artery occlusion, and about 9% of these are symptomatic⁶⁾

Q How common is subclavian steal syndrome?

A

It is found in 2–4% of the general population, but most cases are asymptomatic³⁾. Among patients with peripheral arterial disease, about 30% have subclavian artery stenosis, and even with a large blood pressure difference, many remain asymptomatic⁴⁾.

2. Main symptoms and clinical findings

Central retinal artery occlusion following laser treatment for ocular ischemic aortic arch syndrome. GMS Ophthalmol Cases. 2015 Dec 2; 5:Doc14. Figure 3. PMCID: PMC5015624. License: CC BY.

Fluorescein angiogram showing significantly delayed arterial filling with 60 seconds in the right eye (A) and 52 seconds in the left eye (B) and poor peripheral perfusion. Arteries are attenuated and veins are dilated and non-tortuous in both eyes. The late film (C) shows mild capillary leakage in the right eye at 6 minutes but no macular edema or neovascularization.

Subjective Symptoms

Subjective symptoms of SSS reflect hypoperfusion in the vertebrobasilar artery system.

• Visual symptoms: blurred vision (about 5 minutes per episode, 2–3 times per day), double vision, visual field defects. Some patients report bilateral visual changes as monocular.
• Dizziness and ataxia: rotational vertigo, ataxia, dysarthria, dysphagia
• Syncope and presyncope: recurrent syncope triggered by arm exercise³⁾
• Symptoms in the affected arm: intermittent fatigue, numbness, pain in the arm, worsening with exercise²⁾

Clinical Findings (Findings Confirmed by Physician Examination)

Systemic Findings

• Bilateral arm blood pressure difference: SSS is suspected when the difference is 20 mmHg or more. A difference of 40 mmHg or more corresponds to grade II–III. Representative measurements: a difference of 60 mmHg (right 170/100 vs left 110/70 mmHg) ²⁾, a difference of 40 mmHg ³⁾, and an asymptomatic case with a difference of 70 mmHg ⁴⁾ have been reported.
• Systolic murmur in the neck or supraclavicular fossa: Auscultated over the subclavian artery ³⁾.
• Diminished radial and ulnar artery pulses on the affected side.

Ophthalmic Findings

• Hollenhorst plaque: May extend from the ipsilateral to the contralateral side. Plaques may also be present in both carotid arteries.
• Asymmetry of retinal artery pressure: A report of a left SSS case showed right eye 120/20 gm vs left eye 30/20 gm.
• Asymmetry of ocular pulse amplitude (OPA): In a case of brachiocephalic artery steal syndrome, OPA decreased on the affected side before revascularization and normalized after revascularization.
• Retinal findings: Retinal hemorrhage, dot hemorrhages, microaneurysms (reported in SSS cases due to Takayasu arteritis).
• Incomplete central retinal artery occlusion (CRAO): Short posterior ciliary artery occlusion due to ophthalmic artery spasm.
• Oculomotor nerve palsy: Reported in cases of isolated subclavian artery associated with congenital vascular malformation.

Severity Classification

Grade I (pre-steal)

Decreased vertebral artery blood flow: Antegrade blood flow in the affected vertebral artery is reduced.

No subjective symptoms: Often discovered incidentally on imaging or ultrasound.

Grade II (alternating flow)

Diastolic antegrade, systolic retrograde: The direction of blood flow changes with the pulse.

Mild to moderate symptoms: Symptoms tend to appear during exercise.

Grade III (Persistent Reversal)

Constant retrograde flow: Blood flow in the affected vertebral artery is continuously reversed.

Prominent symptoms: Hypoperfusion symptoms in the vertebrobasilar system occur even at rest.

Q What difference in blood pressure between both arms should raise suspicion of subclavian steal syndrome?

A

A systolic blood pressure difference of 20 mmHg or more raises suspicion of SSS. A difference of 40 mmHg or more corresponds to Grade II–III, but there are cases with a 70 mmHg difference that remain asymptomatic ⁴⁾. It is difficult to predict symptoms based solely on blood pressure difference, and confirmation by ultrasound or imaging is necessary.

3. Causes and Risk Factors

The most common cause of SSS is atherosclerosis, and 81% of patients are reported to have multiple atherosclerotic lesions in the cerebral supply vessels.

Other causes

• Takayasu arteritis / Giant cell arteritis
• Radiation-induced vascular damage
• Thoracic outlet syndrome (compression syndrome)
• Fibromuscular dysplasia
• Neurofibromatosis
• Cervical rib
• After repair of coarctation of the aorta
• Congenital vascular malformation

Risk factors

• Dyslipidemia, hypertension, diabetes mellitus⁶⁾
• Aging (over 50 years old), smoking
• Family history of cardiovascular disease³⁾

Special conditions

• Dialysis-associated SSS: Excessive blood flow in dialysis access can cause or worsen steal syndrome even in patients without subclavian artery stenosis¹⁾
• Coronary-subclavian steal: Occurs after coronary artery bypass grafting using an internal thoracic artery graft. Presents with exertional angina.

Prevention and Daily Care

Most SSS is based on arteriosclerosis. The following measures can help reduce risk.

• Manage hypertension, diabetes, and dyslipidemia as directed by your doctor.
• Smoking cessation is one of the most important preventive measures for vascular diseases including SSS.
• Regularly measure blood pressure in both arms; if the difference is large, consult your doctor.
• If you are on dialysis, discuss the risk of steal syndrome related to vascular access with your primary physician.

Q If I am on dialysis, is my risk of subclavian steal syndrome higher?

A

Excessive blood flow from dialysis access (such as a shunt) can cause SSS-like symptoms even without subclavian artery stenosis ¹⁾. Dizziness and upper limb symptoms during dialysis may be due to this mechanism and require early evaluation.

4. Diagnosis and Testing Methods

Noninvasive Tests

• Bilateral arm blood pressure measurement: The simplest method. Can be performed at the bedside; a difference of 20 mmHg or more suggests SSS.
• Color Doppler ultrasound: First-line noninvasive screening. Detects reversal of vertebral artery blood flow and can simultaneously evaluate stenosis in multiple vessels.
• Transcranial Doppler ultrasound (TCD): Detects blood flow changes in the posterior circulation. Can detect grade I pre-steal components³⁾
• Hyperemia-ischemia cuff test: Detects latent SSS under ultrasound monitoring⁶⁾
• Ophthalmodynamometry: Estimates carotid to ophthalmic artery stenosis by comparing differences in fundus pressure and brachial blood pressure
• Color Doppler imaging (CDI): Analyzes blood flow direction, velocity, and pulse wave changes in the ophthalmic artery, useful for diagnosing ocular ischemic syndrome

Imaging tests

The characteristics of each imaging diagnostic method are shown below.

Examination method	Main use	Features
CTA	Identification of stenosis and calcification assessment	Visualizes occlusion and retrograde filling3)
MRA (TOF method)	Vertebral artery signal evaluation	Decreased signal on the affected side is useful for early diagnosis5)
DSA (cerebral angiography)	Definitive diagnosis and treatment	Gold standard6)

Tanaka et al. (2022) reported a case of a 76-year-old male with recurrent vertigo, in which TOF-MRA showed decreased signal in the left proximal intracranial vertebral artery, and angiography confirmed occlusion of the left subclavian artery origin and left vertebral artery reflux ⁵⁾. They reported that changes in MRA signal intensity are useful for early diagnosis of SSS.

Differential Diagnosis

• Central nervous system: Orthostatic hypotension, cardiac arrhythmia, TIA, epileptic seizures, migraine, arterial dissection
• Upper limb ischemia: Peripheral artery disease, thoracic outlet syndrome, Raynaud’s phenomenon, Takayasu arteritis
• Ocular ischemia: Differentiation from diabetic retinopathy and central retinal vein occlusion is important

5. Standard Treatment

Medical Treatment

Management of risk factors and pharmacotherapy are the mainstays.

• Risk factor management: Control of hypertension, diabetes, dyslipidemia; smoking cessation
• Antiplatelet therapy: DAPT (dual antiplatelet therapy) with aspirin plus clopidogrel ^{2, 6)}, or low-dose aspirin alone ⁴⁾
• Statins: Atorvastatin 40 mg/day or similar ⁶⁾
• Follow-up: Regular monitoring with ultrasound

Ophthalmic treatment for ocular ischemia

• Panretinal photocoagulation: Performed when iris rubeosis or neovascular glaucoma is present
• Intravitreal injection of VEGF inhibitors: Not covered by insurance but sometimes used for neovascular cases
• Evaluation of transient monocular vision loss: Assess stenosis with carotid Doppler ultrasound, rule out arrhythmia. Evaluate the degree of ocular ischemia with electroretinography and fluorescein angiography

Endovascular treatment

The current first-line treatment is percutaneous transluminal angioplasty (PTA) with stent placement.

• 5-year patency rate: 83–89%
• Complications: stroke rate 0.6–1%, minor complications 4.5–5.3% (dissection, TIA, distal embolism, bleeding, etc.)
• Restenosis rate: 10% (decreases to 5% when combined with angioplasty)⁶⁾

Neupane et al. (2024) performed angioplasty plus stent placement for severe proximal left subclavian artery occlusion in a 60-year-old woman²⁾. Postoperative DAPT (aspirin + clopidogrel) plus statin was initiated, and blood flow recovery and symptom resolution were achieved.

Surgical Treatment

This option is selected when endovascular treatment is difficult (e.g., severe calcification) or has failed.

The long-term patency rates for each surgical procedure are shown below.

Procedure	Patency rate
Subclavian artery transposition	5-year 98%
Carotid-subclavian bypass	5-year 95%, 10-year 83%
Carotid-axillary artery bypass	96% at 47 months1)
Axillary-axillary artery bypass	76% at 5 years1)

• Surgical repair outcomes: mortality 0.5%, stroke rate <3.8%
• Indications for carotid-axillary artery bypass: when subclavian artery is heavily calcified and stenting is difficult¹⁾. However, attention must be paid to complications such as phrenic nerve palsy and lymphorrhea¹⁾

Hashimoto et al. (2023) performed common carotid artery to axillary artery bypass using an 8mm PTFE graft in an 83-year-old dialysis patient with severe calcification of the subclavian artery ¹⁾. The patient was discharged on postoperative day 11 and showed no recurrence at 1 year postoperatively.

Treatment Considerations

• The restenosis rate after stenting is 10%, requiring long-term ultrasound follow-up.
• Occlusion or recurrence of SSS after surgical bypass has been reported, with higher recurrence risk in patients with severe vascular disease ⁶⁾.
• In SSS related to dialysis access, blood flow adjustment on the access side is also a treatment option.

Q What are the long-term outcomes of stent treatment?

A

The 5-year patency rate of percutaneous transluminal angioplasty plus stent placement is favorable at 83–89%. However, the restenosis rate is 10%, which decreases to 5% when combined with angioplasty ⁶⁾. Regular follow-up with ultrasound examination is important after surgery.

6. Pathophysiology and Detailed Mechanism

The basic mechanism of SSS is as follows:

1. Stenosis or occlusion of the proximal subclavian artery reduces blood pressure distal to the occlusion.
2. The ipsilateral vertebral artery begins to supply blood retrogradely from the high-pressure basilar artery to the low-pressure subclavian artery.
3. Antegrade blood flow to the vertebrobasilar system decreases, causing hypoperfusion to the occipital lobe, brainstem, and eyes.

Sites of damage due to hypoperfusion in the vertebrobasilar artery system

• Medulla oblongata: Wallenberg syndrome (nystagmus, vertigo, facial sensory disturbance, crossed sensory disturbance)
• Pons: MLF syndrome (internuclear ophthalmoplegia), Foville syndrome, Millard-Gubler syndrome
• Midbrain: Weber syndrome, Benedikt syndrome, Parinaud syndrome (vertical gaze palsy)
• Occipital lobe: Homonymous hemianopia, higher visual dysfunction

Mechanism of ocular ischemia

• Posterior cerebral artery ischemia → reduced blood flow to the occipital visual cortex → cortical visual impairment
• Decreased ophthalmic artery perfusion pressure → retinal and choroidal ischemia → ocular ischemic syndrome

Mechanism of exacerbation during exercise

Using the affected upper limb increases blood flow demand to the arm muscles, increasing blood flow to the distal subclavian artery. This increases “steal” from the vertebral artery, worsening hypoperfusion to the brain and eyes.

Mechanism of dialysis-related SSS

Excessive blood flow from the dialysis access (shunt) increases blood flow demand in the subclavian artery, which can cause vertebrobasilar insufficiency even without obvious stenosis of the subclavian artery¹⁾.

Coronary-subclavian steal

This is a special condition in which, after coronary artery bypass grafting using an internal thoracic artery graft, blood flows backward from the graft into the subclavian artery, causing myocardial ischemia (exertional angina).

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7. Latest research and future prospects (research-stage reports)

For patients: Please read this

The following content is currently at the research stage or under clinical trial and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Early Diagnosis Using MRA Signal Changes

Tanaka et al. (2022) reported a case showing that decreased signal intensity of the affected vertebral artery on TOF-MRA is useful for early diagnosis of SSS ⁵⁾. The role of noninvasive, low-cost MRA as a screening tool before DSA is attracting attention.

Management of Recurrent SSS

Leach et al. (2023) reported a case of a woman in her late 50s with recurrent SSS after left subclavian artery stent occlusion and bypass occlusion ⁶⁾. She had comorbidities including hypertension, type 2 diabetes, dyslipidemia, coronary artery disease, and bilateral carotid artery stenosis, and was confirmed to have recurrent SSS combined with orthostatic cerebral hypoperfusion syndrome (OCHOS). The challenge of establishing recurrence risk and long-term management strategies in patients with severe polyvascular disease is suggested.

Management Guidelines for Asymptomatic SSS

Appropriate management guidelines for asymptomatic SSS have not been established.

Amano et al. (2021) reported an 82-year-old male who was completely asymptomatic despite a systolic blood pressure difference of 70 mmHg ⁴⁾, and discussed the need for intervention in incidentally discovered asymptomatic SSS and the importance of routine bilateral blood pressure measurement.

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8. References

1. Hashimoto K, Kawahara T, Miyoshi K, et al. A case of carotid-axillary bypass for subclavian steal syndrome in an 83-year-old female undergoing hemodialysis. Int J Surg Case Rep. 2023;112:108974.

2. Neupane D, Kafle S, Chhetri V, et al. Subclavian steal syndrome. Clin Case Rep. 2024;12:e8561.

3. Shemesh E, Karkabi B, Zissman K. Multimodality imaging in subclavian steal syndrome. Oxford medical case reports. 2021;2021(7):omab048. doi:10.1093/omcr/omab048. PMID:34306715; PMCID:PMC8297644.

4. Amano Y, Watari T. “Asymptomatic” subclavian steal syndrome. Cureus. 2021;13(10):e19109.

5. Tanaka T, Fukushima K, Goto H, et al. Brain magnetic resonance angiography of subclavian steal syndrome. JMA J. 2022;5(4):551-552.

6. Leach DF 3rd, Radwanski DM, Kaur P, Das DD, Kondapalli M. Recurrent Subclavian Steal Syndrome: A Novel Case of Vasculopathy. Cureus. 2023;15(1):e33310. doi:10.7759/cureus.33310. PMID:36741643; PMCID:PMC9894333.