From the Guidelines
Multiphase flow in the right subclavian artery on ultrasound is typically a normal finding and does not require specific treatment, unless accompanied by symptoms of subclavian steal syndrome or other vascular compromise. When evaluating the right subclavian multiphase flow on ultrasound, it's essential to consider the clinical context and potential symptoms. According to 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, subclavian steal syndrome is a condition where the proximal subclavian artery becomes stenotic or occluded, leading to reversal of flow in the vertebral artery and potential posterior cerebrovascular insufficiency.
Key Considerations
- The presence of multiphase flow in the right subclavian artery on ultrasound may not be pathological in itself, but it's crucial to assess for symptoms such as arm claudication, digital ischemia, or subclavian steal syndrome.
- The diagnosis of subclavian steal syndrome should be considered in patients with symptoms of posterior cerebral circulatory insufficiency aggravated by upper-limb exercise, as stated in the guideline 1.
- Asymptomatic patients with reversal of flow in a vertebral artery or other manifestations of subclavian steal syndrome require no specific intervention other than strategies directed at the secondary prevention of ischemic events related to systemic atherosclerosis, unless the ipsilateral internal mammary artery is required for myocardial revascularization 1.
Clinical Implications
- Correlation with clinical symptoms and additional imaging studies like CT angiography might be warranted if there are concerns about vascular compromise.
- Symptomatic patients should be considered for subclavian revascularization with endovascular or surgical techniques, as recommended in the guideline 1.
From the Research
Right Subclavian Multiphase Flow on US
- The evaluation of right subclavian multiphase flow on ultrasound (US) is crucial for diagnosing subclavian artery stenosis, as seen in studies 2, 3, 4.
- Color Doppler ultrasonography can be used to evaluate symptomatic subclavian artery stenosis, with parameters such as peak systolic velocity (PSV) and acceleration time being significant indicators of stenosis 2.
- A study found that PSV ≥ 230 cm/s and PSVr ≥ 2.2 can predict ≥ 50% stenosis, while PSV ≥ 340 cm/s and PSVr ≥ 3.0 can predict ≥ 70% stenosis 2.
- Another study evaluated the diagnostic value of hemodynamic parameters of color Doppler flow imaging for severe (70-99%) subclavian artery stenosis, finding optimal cutoff values for PSV1, EDV, and PSV1/PSV2 ratio 3.
- Doppler ultrasonography can also be used for patient monitoring after subclavian stenting, with a more than twofold PSV increase being an indicator of restenosis 4.
Diagnostic Parameters
- Peak systolic velocity (PSV) is a significant parameter in evaluating subclavian artery stenosis, with higher values indicating more severe stenosis 2, 3, 4.
- The PSV ratio (PSVr) is also an important parameter, with a ratio ≥ 2.2 indicating ≥ 50% stenosis and ≥ 3.0 indicating ≥ 70% stenosis 2.
- End diastolic velocity (EDV) and the PSV1/PSV2 ratio are also useful parameters in evaluating severe subclavian artery stenosis 3.
Treatment and Monitoring
- Percutaneous transluminal angioplasty (PTA) with stent placement is a common treatment for subclavian artery stenosis, with studies showing its effectiveness in maintaining patency and reducing symptoms 5, 4.
- Doppler ultrasonography can be used to monitor patients after subclavian stenting, allowing for early detection of restenosis and prompt intervention 4.