What is the management of retrograde flow to the right vertebral artery?

Retrograde Flow to Right Vertebral Artery: Definition and Management

What It Is

Retrograde flow in the right vertebral artery represents blood flowing backward (toward the arm rather than toward the brain), most commonly caused by proximal subclavian artery stenosis or occlusion—this is the hallmark of subclavian steal syndrome. 1, 2

• When the dominant vertebral artery is subtended by subclavian obstruction, reversal of flow reduces basilar artery perfusion and causes posterior cerebrovascular insufficiency 1
• Atherosclerosis is the most common cause, though Takayasu arteritis, giant cell arteritis, fibromuscular dysplasia, and radiation-induced arteriopathy can also be responsible 1, 2
• Less commonly, retrograde vertebral flow occurs from increased subclavian flow (such as with dialysis access fistulas) rather than stenosis 3

Clinical Presentation to Assess

Symptoms are typically aggravated by exercising the ipsilateral arm, which amplifies the flow reversal. 1

Posterior Circulation Symptoms

• Lightheadedness, syncope, vertigo, ataxia, diplopia, motor deficits 1, 2
• Visual disturbances, dysphasia, dysarthria, confusion, facial sensory deficits 2
• Perioral numbness, blurred vision, tinnitus, bilateral sensory deficits 1

Upper Extremity Symptoms

• Arm or hand claudication, paresthesia, rest pain 1
• Digital ischemia, coldness or numbness in the affected arm 2

Physical Examination Findings

• Blood pressure asymmetry between arms >10-15 mmHg (lower pressure on affected side) is a key diagnostic finding 2
• Periclavicular or infraclavicular bruit suggests subclavian stenosis 1, 2

Important caveat: Many patients with subclavian steal are asymptomatic despite having flow reversal in the vertebral artery, and retrograde flow per se is a benign entity. 2, 4

Diagnostic Approach

First-Line Imaging

• Duplex ultrasonography can identify reversal of flow in the vertebral artery with intrastenotic high-velocity flows and monophasic post-stenotic waveforms 1, 2
• Bidirectional flow (retrograde in systole, antegrade in diastole) indicates incomplete reversal 3, 4

Advanced Imaging

• CT angiography or MR angiography of the aortic arch identifies the location and severity of subclavian artery stenosis 2, 5
• Imaging in multiple arm positions (neutral and abducted/elevated) assesses dynamic arterial compression 5
• Sagittal reformations are essential because axial slices alone underestimate stenosis in 43% of cases 5
• MRA with contrast distinguishes anterograde from retrograde perfusion 5
• Catheter angiography remains the gold standard but is typically reserved for cases where endovascular intervention is planned 1, 5

Management Algorithm

Asymptomatic Patients

Routine revascularization is NOT recommended in asymptomatic patients with subclavian steal syndrome. 2

• Exception: Patients requiring myocardial revascularization where the ipsilateral internal mammary artery is needed for coronary artery bypass grafting 1, 2
• During follow-up, asymptomatic patients do not become symptomatic, and there are no strokes or stroke-related deaths 4

Symptomatic Patients

Symptomatic patients should be considered for subclavian revascularization using either endovascular or surgical techniques. 1, 2

Endovascular Options

• Balloon angioplasty, atherectomy, and stenting have high initial success rates (93-98%) 2
• Lower long-term patency compared to surgery 2
• No randomized trials have compared endovascular methods with surgical revascularization 1

Surgical Options (Preferred for Long-Term Patency)

• Carotid-subclavian bypass with prosthetic grafting has excellent long-term patency (96-100% at 5 years) 2
• Other extra-anatomic revascularization methods include carotid-axillary or axilloaxillary bypass and subclavian-carotid arterial transposition 1
• Surgical repair is associated with low morbidity and mortality 1

Medical Management

Despite the paucity of evidence specific to vertebral artery disease, medical management should follow guidelines for carotid artery disease. 1

• For acute ischemic syndromes involving the vertebral artery territory with angiographic evidence of thrombus, anticoagulation is generally recommended for at least 3 months 1
• Aspirin and warfarin are equally efficacious after initial non-cardioembolic ischemic stroke 1
• Ticlopidine was superior to aspirin for secondary prevention in patients with symptomatic posterior circulation disease 1
• Aspirin plus dipyridamole reduced vertebrobasilar territory stroke/TIA to 5.7% compared with 10.8% for placebo 1

Critical Pitfalls to Avoid

• Do not assume symptoms are due to vertebrobasilar insufficiency without excluding cardiac arrhythmias, orthostatic hypotension, and vestibular disorders 1
• Surgical procedures that restore antegrade vertebral artery flow do not necessarily improve symptoms of posterior circulation ischemia 4
• Accurate selection of surgical candidates remains imprecise and requires not only identification of vertebrobasilar disease but also confirmation that symptoms are due to these stenoses 4
• An inter-arm systolic blood pressure difference >25 mmHg is associated with doubled mortality risk and should prompt immediate evaluation 2