From the Guidelines
The best initial test to evaluate suspected subclavian or axillary artery stenosis or occlusion is duplex ultrasonography, specifically US Duplex Doppler Subclavian Artery and Vein, as it is an excellent initial study in the evaluation of arterial stenosis and thrombosis 1. This non-invasive imaging modality combines B-mode ultrasound with Doppler flow analysis to visualize the vessels and assess blood flow characteristics. The advantages of duplex ultrasonography as a first-line test include its wide availability, lack of radiation exposure, and absence of contrast requirements. The test can effectively detect stenosis by identifying areas of increased flow velocity, turbulence, and post-stenotic flow disturbances. It can also directly visualize occlusions and collateral circulation patterns. For optimal results, the examination should include assessment of both upper extremities to allow comparison of blood flow patterns and pressures. Some key points to consider when using duplex ultrasonography for this purpose include:
- Direct visualization of the subclavian and axillary arteries for aneurysmal change, arterial stenosis, and thrombosis 1
- Assessment of dynamic arterial blood flow during abduction to identify changes in peak velocity or reproducible symptoms indicative of stenosis or occlusion 1
- Evaluation of the cross-sectional area of the costocervical space for potential compression or other pathology 1 While duplex ultrasonography may have limitations in visualizing the proximal subclavian artery due to interference from the clavicle or lung tissue, it remains the preferred initial test due to its safety profile and diagnostic capabilities, as supported by the most recent guidelines 1. If duplex findings are inconclusive or if intervention is planned, more advanced imaging such as CT angiography or conventional angiography may subsequently be required, as suggested in other studies 1.
From the Research
Initial Test for Suspected Subclavian or Axillary Artery Stenosis or Occlusion
To evaluate suspected subclavian or axillary artery stenosis or occlusion, the best initial test can be determined based on the available evidence.
- Duplex Ultrasound: This non-invasive method is highly effective for detecting stenosis or occlusion in peripheral arterial disease, including subclavian and axillary arteries 2, 3. It provides detailed information on the location, extent, and severity of the disease.
- Characteristics of Arterial Duplex Testing: Understanding the features of duplex-acquired velocity spectra recordings is fundamental to accurate diagnostic testing, including the characteristic spectral features of "normal" versus "abnormal" arterial flow, hemodynamic changes associated with stenosis or occlusion 4.
- Velocity Criteria: A subclavian artery flow velocity exceeding 240 cm/s seems to be predictive of significant subclavian stenosis, as proposed by new subclavian duplex ultrasound velocity criteria 2.
- Comparison with Other Imaging Modalities: While computed tomography angiography (CTA) is also used for evaluating arterial stenosis or occlusion, duplex ultrasound has been found to be less accurate than CTA in evaluating iliac arterial diseases but shows good diagnostic concordance with digital subtraction angiography (DSA) in detecting hemodynamic stenosis and occlusion of the femoro-popliteal axis 5.
- Clinical Findings and Ultrasonographic Results: Continuous-wave (CW) Doppler sonography has proved to be a reliable tool for detecting subclavian stenosis or occlusion and reversal of blood flow in the vertebral artery, with the incidence of subclavian stenosis or occlusion found to be 1.15% among examined patients 3.
Given the evidence, duplex ultrasound appears to be a suitable initial test for evaluating suspected subclavian or axillary artery stenosis or occlusion due to its non-invasive nature, effectiveness in detecting stenosis or occlusion, and the availability of established velocity criteria for interpreting results 6, 2, 3.