What are the diagnostic tests for Subclavian Steal Syndrome?

From the Guidelines

Subclavian steal syndrome is best diagnosed through a combination of imaging studies, with duplex ultrasound being the initial test of choice, as recommended by the 2024 ESC guidelines for the management of peripheral arterial and aortic diseases 1. This non-invasive test can detect reversed flow in the vertebral artery and stenosis in the subclavian artery. If ultrasound findings are suggestive, CT angiography (CTA) or magnetic resonance angiography (MRA) should follow to provide detailed anatomical information about the stenosis location and severity, as outlined in the 2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS guideline on the management of patients with extracranial carotid and vertebral artery disease 1. Some key points to consider when testing for subclavian steal syndrome include:

• Bilateral arm blood pressure measurement is recommended for all patients with peripheral arterial and aortic diseases, as stated in the 2024 ESC guidelines 1
• A difference greater than 20 mmHg in blood pressure between the two arms is suggestive of subclavian stenosis, as mentioned in the example answer
• Exercise testing of the affected arm can sometimes provoke symptoms and demonstrate the steal phenomenon, as noted in the 2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS guideline 1
• Transcranial Doppler can also be useful to assess blood flow changes in the vertebrobasilar system during arm exercise, as recommended in the 2024 ESC guidelines 1 These tests are important because subclavian steal syndrome occurs when stenosis of the subclavian artery proximal to the vertebral artery origin causes blood to flow retrograde in the ipsilateral vertebral artery, potentially causing vertebrobasilar insufficiency symptoms like dizziness, visual disturbances, and ataxia, particularly during arm exercise, as described in the 2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS guideline 1. The diagnosis and management of subclavian steal syndrome should be individualized, taking into account the patient's symptoms, the severity of the stenosis, and the presence of other comorbidities, as recommended in the 2024 ESC guidelines 1.

From the Research

Subclavian Steal Syndrome Testing

• Subclavian steal syndrome is a condition characterized by retrograde blood flow in the vertebral artery, often caused by significant subclavian or innominate artery obliteration 2.
• The syndrome can be diagnosed using non-invasive techniques such as Doppler ultrasound, which can determine the direction of flow in the vertebral arteries 2, 3.
• Doppler ultrasonography can also be used to monitor patients after subclavian stenting and detect restenosis 4.
• Other diagnostic modalities include CT or MR angiography, which can confirm the diagnosis of subclavian steal syndrome 3, 5.
• The diagnosis of subclavian steal syndrome should be considered in patients with discrepant arm blood pressures, diminished or weakened radial pulse, vertebral-basilar symptoms, or arm ischemia 6.

Diagnostic Techniques

• Doppler ultrasound is a useful screening tool for subclavian steal syndrome, with high reliability and accuracy 2, 4.
• CT or MR angiography can provide detailed images of the subclavian and vertebral arteries, confirming the diagnosis of subclavian steal syndrome 3, 5.
• Duplex ultrasound can confirm inverted vertebral artery flow, which is a characteristic feature of subclavian steal syndrome 5.
• Multi-slice computed tomography angiography can provide detailed images of the subclavian and vertebral arteries, confirming the diagnosis of subclavian steal syndrome 5.

Clinical Correlation

• Subclavian steal syndrome can cause symptoms such as paroxysmal vertigo, drop attacks, and arm claudication due to compromised vertebrobasilar and brachial blood flows 3.
• The syndrome can also cause transient ischemic attacks (TIAs) due to decreased blood flow to the brain 5.
• Atherosclerosis of the subclavian artery is the most common cause of subclavian steal syndrome 3.
• The diagnosis and treatment of subclavian steal syndrome require a multidisciplinary approach, involving vascular surgeons, radiologists, and other healthcare professionals 3, 5.