From the Guidelines
Subclavian steal syndrome is characterized by reversed blood flow in the vertebral artery due to proximal subclavian artery stenosis or occlusion, with primary features including arm claudication, vertebrobasilar insufficiency symptoms, and a blood pressure difference of more than 20 mmHg between arms. The syndrome is often asymptomatic and discovered incidentally, with symptoms more likely to occur during arm exercise when blood is "stolen" from the brain to supply the arm 1. Risk factors include atherosclerosis, smoking, diabetes, and hypertension.
Key Features
- Arm claudication (pain, fatigue, or weakness in the affected arm with exertion)
- Vertebrobasilar insufficiency symptoms (dizziness, vertigo, visual disturbances, ataxia, syncope)
- Blood pressure difference of more than 20 mmHg between arms
- Diminished or absent pulses in the affected arm
- Bruit over the supraclavicular area
Diagnosis
Diagnosis involves vascular imaging such as duplex ultrasound, CT angiography, or MR angiography to confirm the stenosis and flow reversal 1. Duplex ultrasound assessment of subclavian arteries enables the detection of subclavian steal syndrome via intrastenotic high-velocity flows or monophasic post-stenotic waveforms.
Treatment
Treatment depends on symptom severity, ranging from conservative management of cardiovascular risk factors to endovascular procedures like angioplasty with stenting or surgical bypass for severely symptomatic patients 1. Asymptomatic patients with asymmetrical upper-limb blood pressure, reversal of flow in a vertebral artery, or other manifestations of subclavian steal syndrome need 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.
From the Research
Features of Subclavian Steal Syndrome
The features of subclavian steal syndrome (SSS) include:
- Retrograde blood flow in the vertebral artery due to significant stenosis or occlusion of the proximal subclavian artery or the innominate artery 2
- Symptoms such as dizziness, vertigo, blurred vision, diplopia, headache, syncope, postural hypotension, neurologic deficits, and rarely, memory problems 3
- Arm claudication, which is a result of the arm getting blood supply from the vertebral artery at the expense of the vertebrobasilar system 3
- Difference in blood pressure levels between the right and left arms 4
- Bruit of the subclavian area 4
- Paroxysmal vertigo, drop attacks, and/or arm claudication 5
Clinical Presentation
The clinical presentation of SSS can vary, but it is often characterized by:
- Asymptomatic cases, which are more common in patients with atherosclerotic SSS forms 2
- Symptomatic cases, which are more frequent in patients with SSS due to dialysis arteriovenous fistulas (AVFs) 2
- Symptoms that occur during hemodialysis sessions, such as vertebrobasilar insufficiency and resting pain of the upper extremity 6
Diagnostic Findings
The diagnostic findings of SSS include:
- Noninvasive studies that demonstrate a preocclusive stenosis at the origin of the subclavian artery, together with a stenosis on the internal carotid artery superior to 70% and reversion of flow in the vertebral artery 6
- Doppler ultrasound as a useful screening tool, but the diagnosis must be confirmed by CT or MR angiography 5
- Coronary angiography that reveals retrograde flow from the coronary artery via the internal mammary artery (IMA) and the vertebral artery to the subclavian artery due to a proximal subclavian artery stenosis 4