Prevalence and impact of the subclavian steal syndrome

To determine the prevalence and impact of subclavian steal syndrome (SSS) in patients undergoing assessment of the carotid arteries.

Vertebral artery flow reversal is often found among patients undergoing imaging of the extracranial vessels; however, there are no large studies evaluating the prevalence and natural history of SSS in stratified patients.

Patients presenting for duplex ultrasound of the carotid arteries underwent 2 sets of bilateral arm pressure measurements. Patients with a pressure differential (PD) >20 mm Hg were examined in detail for vascular obstruction ipsilateral to the affected arm. When appropriate, computer tomographic angiography (CTA), magnetic resonance angiography, and angiography were performed. Signs and symptoms related to SSS and the types of interventions performed were recorded.

In a period of 6 years, 7881 carotid duplex scans were performed, with a PD >20 mm Hg in 514 (6.5%) patients and a left arm preponderance (82%). SSS was complete in 61%, partial in 23%, and absent in 16%. Symptoms were present in 38 patients with 32 experiencing symptoms of the posterior circulation, 4 of arm ischemia, and 2 of cardiac ischemia. Symptoms occurred more frequently as the arm PD increased. Of the 38 symptomatic patients, only 7 underwent an intervention (2 with subclavian-carotid bypass and 5 with percutaneous transluminal angioplasty stenting of the subclavian).

SSS is a frequent finding in patients undergoing carotid duplex scanning. Patients are commonly asymptomatic and rarely require an intervention. A significantly elevated arm PD (>40-50 mm Hg) is more commonly associated with symptoms, complete steal, and the need for intervention.