Subclavian Steal Syndrome Diagnosis and Management

Definition and Pathophysiology

Subclavian steal syndrome occurs when proximal subclavian artery stenosis or occlusion causes retrograde blood flow in the ipsilateral vertebral artery, leading to posterior cerebral circulatory insufficiency and upper extremity symptoms 3
Atherosclerosis is the most common cause, but other etiologies include Takayasu arteritis, giant cell arteritis, fibromuscular dysplasia, and radiation-induced arteriopathy 3

Symptoms may include vertebrobasilar insufficiency (dizziness, vertigo, blurred vision, alternating hemiparesis, dysphasia, dysarthria, confusion, loss of consciousness, drop attacks, ataxia) 4
Upper extremity claudication, characterized by exercise-induced crampy pain and fatigue in the affected arm 4, 3
Patients with coronary bypass using the internal mammary artery can develop myocardial ischemia as a manifestation of subclavian steal 4

The American College of Cardiology and European Heart Journal recommend that an inter-arm blood pressure difference of >15-20 mmHg is abnormal and suggestive of subclavian (or innominate) artery stenosis 1, 2
The European Heart Journal notes that an absolute inter-arm systolic blood pressure difference >10-15 mmHg is suspicious for subclavian stenosis 2
An inter-arm systolic blood pressure difference >25 mmHg doubles prevalence and independently predicts mortality 2
Bilateral arm blood pressure measurement is recommended for all patients with peripheral arterial disease 2

Duplex ultrasonography can identify reversal of flow in the vertebral artery, with intrastenotic high-velocity flows (50% stenosis: peak systolic velocity ≥230 cm/s) and monophasic post-stenotic waveforms 2, 3
More than 90% of patients with at least 50% proximal subclavian stenosis have either intermittent or continuous flow reversal in the vertebral artery 2
CT angiography or MR angiography of the aortic arch can definitively identify stenosis of the subclavian artery 3
Arteriography can assess the entire arterial tree from aortic arch to palmar arch in cases of suspected steal syndrome 5

The American College of Cardiology recommends that asymptomatic subclavian steal generally does not require intervention 1, 3
In symptomatic patients with atherosclerotic subclavian artery disease (TIA/stroke, coronary subclavian steal syndrome), both endovascular and surgical revascularization options should be considered 2
Endovascular revascularization may be preferred over surgery due to lower complication rates, despite similar long-term outcomes 2
Surgical options like carotid-subclavian bypass have excellent long-term patency (96-100% at 5 years) 3

Patients with peripheral arterial disease have a higher prevalence of subclavian stenosis (11.4% vs. 4.5% in general population) 2
The natural history of subclavian steal appears relatively benign in most cases, but patients should be monitored for progression 4

Measuring blood pressure in both arms identifies the arm with the highest systolic pressure, which is required for accurate measurement of the ankle-brachial index 1
Identification of unequal blood pressures in the arms allows for more accurate measurement of blood pressure in the treatment of hypertension 1
The presence of a periclavicular or infraclavicular bruit may indicate subclavian stenosis 3
Not all patients with flow reversal in the vertebral artery will be symptomatic 2