From the Guidelines
The best diagnostic test for subclavian artery stenosis is duplex ultrasonography, which should be used as the initial imaging modality. This non-invasive test combines B-mode ultrasound with Doppler flow studies to visualize the vessel and assess blood flow patterns, enabling the detection of high-velocity flows indicating >50% stenosis 1. For more definitive evaluation, CT angiography (CTA) or magnetic resonance angiography (MRA) are excellent second-line options, with CTA offering superior spatial resolution and detailed anatomical information 1.
Key Considerations
- Duplex ultrasonography is the recommended initial imaging modality due to its non-invasive nature and ability to detect significant stenosis.
- CTA and MRA are useful for more definitive evaluation, with CTA providing superior spatial resolution and detailed anatomical information.
- Digital subtraction angiography remains the gold standard for diagnosis but is typically reserved for cases requiring intervention due to its invasive nature and associated risks.
- When evaluating patients with suspected subclavian stenosis, clinicians should also perform a physical examination including bilateral blood pressure measurements to check for a difference greater than 15-20 mmHg between arms, which suggests significant stenosis 1.
Diagnostic Approach
- The choice of diagnostic test should consider the patient's clinical presentation, risk factors such as smoking or atherosclerosis, and the presence of symptoms like arm claudication, subclavian steal syndrome, or vertebrobasilar insufficiency.
- MRA may help identify the severity of thoracic outlet syndrome (TOS) and guide surgical or endovascular management, and can be used to evaluate interval changes in the thoracic outlet, assess adequate decompression, and confirm arterial patency 1.
From the Research
Diagnostic Tests for Subclavian Artery Stenosis
The diagnosis of subclavian artery stenosis can be achieved through various imaging techniques. The choice of diagnostic test depends on the severity of the stenosis and the presence of symptoms.
- Computed Tomography Angiography (CTA): CTA is a highly accurate diagnostic test for subclavian artery stenosis, with a high concordance rate with digital subtraction angiography (DSA) in grading subclavian artery stenosis 2.
- Color Doppler Ultrasonography: Color Doppler ultrasonography is a non-invasive diagnostic test that can evaluate subclavian artery stenosis, with optimal cutoff values of peak systolic velocity (PSV) ≥ 230 cm/s and PSV ratio (PSVr) ≥ 2.2 to predict ≥ 50% stenosis 3.
- Digital Subtraction Angiography (DSA): DSA is considered the gold standard for diagnosing subclavian artery stenosis, but it is an invasive procedure 4, 5, 6.
- Subclavian Duplex Ultrasound: Subclavian duplex ultrasound is a non-invasive diagnostic test that can evaluate subclavian artery stenosis, with a proposed cutoff value of > 240 cm/s to predict significant subclavian stenosis 5.
Comparison of Diagnostic Tests
The diagnostic tests for subclavian artery stenosis have varying degrees of accuracy and invasiveness. CTA and color Doppler ultrasonography are non-invasive tests with high accuracy, while DSA is an invasive test considered the gold standard.
- Accuracy: CTA has a high concordance rate with DSA, while color Doppler ultrasonography has optimal cutoff values to predict ≥ 50% stenosis 2, 3.
- Invasiveness: CTA and color Doppler ultrasonography are non-invasive tests, while DSA is an invasive procedure 4, 5, 6.
Clinical Implications
The choice of diagnostic test for subclavian artery stenosis depends on the clinical presentation and the presence of symptoms. Symptomatic patients with ultrasonic parameters of PSV ≥ 230 cm/s and PSVr ≥ 2.2 may need to be considered for further verification by CTA or MRA, or by DSA with a view to percutaneous transluminal angioplasty/stent implantation in the same session 3.