Overview
Definition:
Subclavian steal syndrome (SSS) is a condition characterized by stenosis or occlusion of the subclavian artery proximal to the origin of the vertebral artery, causing retrograde flow in the vertebral artery and symptoms of vertebrobasilar insufficiency
Stenting is a minimally invasive endovascular technique used to restore antegrade flow and alleviate symptoms.
Epidemiology:
It is estimated to affect 0.1% to 0.5% of the general population, with higher prevalence in older individuals and those with significant atherosclerotic risk factors
Men are more commonly affected than women
The left subclavian artery is more frequently involved than the right.
Clinical Significance:
Unmanaged SSS can lead to significant morbidity due to inadequate blood supply to the brain and upper extremity
Prompt diagnosis and intervention are crucial to prevent debilitating neurological events such as stroke, transient ischemic attacks (TIAs), and to improve upper limb perfusion and function
Understanding the surgical interface is vital for residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Arm claudication with exertion
Inequality of blood pressure between arms
Vertigo
Dizziness
Tinnitus
Visual disturbances
Syncope
Hemiparesis or hemiplegia
Dysarthria
Nausea
Vomiting
Ataxia.
Signs:
Diminished or absent radial pulse on the affected side
Blood pressure differential > 20 mmHg between arms
Subclavian bruit, typically heard in the supraclavicular fossa
Symptoms exacerbated by arm exercise
Pallor or cyanosis of the affected arm.
Diagnostic Criteria:
No single definitive diagnostic criteria exist, but a combination of clinical suspicion, physical findings, and characteristic imaging findings is used
Key elements include a significant pressure gradient between arms, neurological symptoms consistent with vertebrobasilar insufficiency, and imaging evidence of subclavian artery stenosis or occlusion with retrograde vertebral artery flow.
Diagnostic Approach
History Taking:
Detailed inquiry regarding neurological symptoms (transient or permanent), arm symptoms (pain, weakness, fatigue) with exertion, and comparison of blood pressures
Assess for risk factors for atherosclerosis (hypertension, diabetes, hyperlipidemia, smoking)
Ask about previous vascular procedures or radiation therapy to the chest/neck.
Physical Examination:
Bilateral arm blood pressure measurement, noting significant discrepancies
Palpation of radial and brachial pulses for amplitude and symmetry
Auscultation for supraclavicular bruits
Neurological examination to assess for focal deficits, cranial nerve dysfunction, and cerebellar signs
Examination of the upper extremities for signs of ischemia.
Investigations:
Duplex ultrasonography: Initial non-invasive assessment of subclavian artery stenosis and flow patterns
Arteriography (Digital Subtraction Angiography - DSA): Gold standard for anatomical definition of stenosis, collateralization, and planning endovascular intervention
CT Angiography (CTA) or MR Angiography (MRA): Non-invasive imaging modalities to visualize the subclavian and vertebral arteries, providing detailed anatomical information.
Differential Diagnosis:
Thoracic outlet syndrome
Vertebral artery dissection
Basilar artery migraine
Atherosclerotic intracranial stenosis
Aortic arch syndrome
Cervical spondylosis with cord compression
Transient ischemic attack (TIA) of other etiology.
Surgical Interface
Indications For Stenting:
Symptomatic subclavian artery stenosis or occlusion causing vertebrobasilar insufficiency or significant arm ischemia
Asymptomatic stenosis > 50-70% in patients with a highly tortuous vertebral artery or severe intracranial disease may be considered for intervention
Documented pressure gradient across the stenosis.
Preoperative Preparation:
Comprehensive risk assessment (cardiac, renal)
Review of imaging studies to confirm anatomy, severity of stenosis, and suitability for endovascular approach
Peri-procedural anticoagulation and antiplatelet therapy initiation
Patient counselling regarding procedure, risks, benefits, and alternatives
Informed consent.
Procedure Steps:
Access: Typically via femoral artery puncture (Seldinger technique)
Catheterization: Guidewire and diagnostic catheter advanced into the aortic arch and selected subclavian artery
Angiography: Baseline arteriogram to confirm lesion and assess collateral flow
Angioplasty: Balloon angioplasty performed across the stenosis to dilate the artery
Stenting: Deployment of a self-expanding or balloon-expandable stent across the stenotic segment, ensuring adequate coverage of the lesion
Post-stent Angiography: To confirm satisfactory stent deployment and restoration of antegrade flow, with resolution of retrograde vertebral flow
Access site closure.
Intraoperative Monitoring:
Continuous electrocardiogram (ECG) monitoring for arrhythmias
Blood pressure monitoring to detect hypotension or hypertension
Neurological status monitoring for any signs of acute ischemia
Fluoroscopic guidance for precise catheter and stent placement
Doppler assessment of limb perfusion if available.
Postoperative Care
Immediate Postoperative Care:
Hemodynamic monitoring and management
Pain control
Assessment of access site for bleeding or hematoma
Neurological assessment for any new or worsening deficits
Administration of post-procedure anticoagulation/antiplatelet therapy as per protocol.
Medications:
Dual antiplatelet therapy (aspirin and clopidogrel or ticagrelor) initiated per institutional protocol, typically for at least 6-12 months post-stenting
Long-term aspirin therapy may be recommended
Statins for lipid management
Blood pressure control medications as needed.
Follow Up:
Regular clinical follow-up at 1, 6, and 12 months, then annually
Assessment of symptom resolution
Blood pressure checks
Duplex ultrasonography or CTA/MRA at intervals to assess stent patency and identify in-stent stenosis
Emphasis on lifestyle modifications and secondary prevention of atherosclerosis.
Complications
Early Complications:
Access site complications (hematoma, pseudoaneurysm, arteriovenous fistula)
Distal embolization leading to stroke or transient ischemic attack (TIA)
Artery dissection or perforation
Stent malapposition or migration
Acute stent thrombosis
Allergic reaction to contrast media
Bleeding or retroperitoneal hemorrhage.
Late Complications:
In-stent restenosis (ISR) due to neointimal hyperplasia
Late stent thrombosis
Recurrent stenosis proximal or distal to the stent
Persistent or recurrent symptoms
Endoleak if a covered stent is used.
Prevention Strategies:
Meticulous technique during vascular access and catheter manipulation
Appropriate stent selection and deployment
Aggressive use of antithrombotic therapy
Careful patient selection and risk stratification
Optimizing angioplasty technique to minimize vessel trauma.
Key Points
Exam Focus:
Recognize the classic presentation of subclavian steal syndrome
Understand the indications for stenting versus bypass surgery
Master the interpretation of arteriographic findings and duplex ultrasound
Recall the critical importance of antiplatelet therapy post-stenting.
Clinical Pearls:
Always measure bilateral arm blood pressures
A significant gradient (>20 mmHg) and a supraclavicular bruit are highly suggestive
Exercise stress testing of the arm can unmask subtle symptoms
Consider SSS in patients with unexplained neurological events or arm symptoms, especially with atherosclerotic risk factors.
Common Mistakes:
Attributing all arm or neurological symptoms to other causes without considering subclavian steal
Inadequate imaging leading to misdiagnosis of stenosis severity
Premature discontinuation of dual antiplatelet therapy, increasing the risk of stent thrombosis
Failure to adequately assess for concomitant coronary or carotid artery disease.