Presentation
Intermittent claudication of left arm.
Patient Data
The distal left subclavian artery and brachial artery spectral analysis showed spectral broadening, monophasic flow and dampened velocity (compare it with the right one) giving tardus parvus flow pattern suggesting proximal left subclavian artery stenosis or occlusion. Additionally, the left vertebral artery has retrograde flow direction similar to the left vertebral vein which is in contrary to the normal antegrade flow seen on the right vertebral artery. Also, the left vertebral artery has decreased flow velocity compared to the normal contralateral side.
There is complete occlusion of the left subclavian proximal segment seen as complete contrast filling defect.
Case Discussion
Subclavian steal phenomenon means to steno-occlusive disease of the proximal subclavian artery with retrograde flow in the ipsilateral vertebral artery. Usually, the left subclavian artery is involved because its acute angle at its origin increases turbulent flow and accelerates atherosclerosis at its proximal segment. The left vertebral artery serves as a collateral to supply the subclavian artery distal to the occlusion/stenosis, thereby stealing blood from the posterior circulation. Whether or not this phenomenon causes cerebral ischemic symptoms depends on posterior communicating arteries. If the patient has associated neurologic symptoms, we call it subclavian steal syndrome.
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