Approach Considerations
After an adequate physical examination, routine laboratory studies should be ordered to address risk factors for atherosclerosis. These tests should include a fasting lipid profile and blood glucose.
Imaging studies that may be considered include duplex ultrasonography (US), computed tomography (CT) angiography (CTA), four-vessel cerebral arteriography, magnetic resonance angiography (MRA), and chest radiography. [7] (See Subclavian Steal Syndrome Imaging.) Electrocardiography (ECG) may also be considered.
Ultrasonography
Duplex US is the most important test of the extracranial carotid and vertebral arteries, as well as the subclavian artery. It can demonstrate retrograde blood flow in the vertebral artery and any significant occlusive lesions of the carotid arteries in the neck.
Subclavian steal syndrome is now most commonly diagnosed during Doppler US examination of the neck arteries. [8] In most cases, because of anatomic constraints imposed by the chest wall, it is difficult to assess the proximal subclavian artery adequately by means of US.
Angiography
Searching for significant lesions in the ipsilateral carotid artery is important. If brachial artery pressures are significantly decreased (>20%) in comparison with the contralateral side, arch aortography should be performed to further define the problem and plan for operative or interventional repair.
Although conventional angiography remains the gold standard investigation for the diagnosis of subclavian occlusive disease in most centers, CTA has replaced this modality as the first-line test. It has a high sensitivity and specificity and has the advantage of being able to identify other lesions in the arch vessels. No arterial puncture is required. Currently, CTA is regarded as excellent for planning and sizing in endovascular treatment, and only rarely is conventional four-vessel arteriography required.
Four-vessel cerebral arteriography can define the problem anatomically, demonstrating retrograde blood flow in the vertebral artery and associated proximal occlusive subclavian artery lesions. In addition, arteriography serves as a road map for possible repair (surgical or endovascular) of the subclavian artery.
MRA has become an alternative to conventional angiography for the assessment of subclavian steal syndrome, especially in patients with renal dysfunction. Unfortunately, however, MRA often overestimates the degree of arterial obstruction and is associated with a higher degree of false-positive results.
Other Tests
Chest radiography is performed to look for unusual causes of subclavian artery obstruction (eg, cervical rib).
Because many of these patients have concomitant ischemic heart disease, ECG is advisable.
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Irregular proximal subclavian stenosis.
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Retrograde blood flow from left vertebral artery into left subclavian artery in patient with subclavian steal syndrome.
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Successful stent treatment of subclavian stenosis, with restored antegrade flow into vertebral artery.
