“Stealing” from a Subclavian Steal: A Case Study

Abstract

A 51-year-old woman was seen with new-onset right hemispheric transient ischemic attacks consisting of left arm weakness and light-headedness. Previous medical history included medically controlled hypertension and coronary artery bypass. A carotid duplex study 2 years previously revealedless than 60% internal carotid stenosis bilaterally. The left subclavian artery signal was abnormal, and the flow in the left vertebral had a to-and-fro signal consistent with early subclavian steal. Carotid duplex ultrasonography was performed on this admission and again demonstrated hemodynamically insignificant stenosis in the internal carotid arteries. Flow in the left vertebral artery was antegrade with normal flow characteristics. The velocities in the right common carotid (CCA), subclavian, and vertebral arteries were low (CCA peak systolic velocity [PSV] of 58 cm/sec versus the left CCA PSV of 102 cm/sec) with tardus parvus waveforms, consistent with proximal obstructive disease. The innominate artery had a poststenotic signal with a PSV of 200 cm/sec. Angiography revealed 90% stenosis at the origin of the innominate artery and 50% stenosis of the left subclavian artery. Angioplasty and stenting of the innominate lesion was performed with an excellent radiographic result. Carotid duplex ultrasonography was performed 2 weeks after stent placement. Flow velocities and waveforms were significantly improved in the right CCA (PSV of 68 cm/sec versus 72 cm/sec on the left). Signals in the subclavian and vertebral arteries were also improved. The left vertebral signal was again abnormal and consistent with early subclavian steal. The varying flow direction in the left vertebral artery is of interest and demonstrates the hemodynamic effects of severe extracranial cerebrovascular disease. In this patient with left subclavian stenosis and steal, when the innominate stenosis became severe enough to decrease the flow to the brain, flow in the left vertebral reversed from a to-and-fro signal to antegrade flow. After angioplasty and stenting of the innominate lesion, flow in the left vertebral artery reverted to one consistent with subclavian steal.