Subclavian Steal Syndrome

Stenosis / occlusion of proximal subclavian artery (proximal to vertebral artery origin) — usually atherosclerotic; rarely Takayasu's, fibromuscular dysplasia, prior radiation, post-surgical. During arm exertion, demand exceeds supply → blood 'stolen' from vertebral artery (retrograde flow) → posterior circulation insufficiency. Features: • Arm: claudication, weakness, paraesthesia, cold arm (with exertion). • Asymmetric arm BP (>15 mmHg difference) and/or weak / absent radial pulse on affected side. • Posterior circulation symptoms: vertigo, visual disturbance, syncope, ataxia, dysarthria — typically with arm exertion. • Coronary-subclavian steal: angina post-CABG with LIMA graft + subclavian stenosis (chest pain on arm exertion). Workup: • Bilateral arm BPs. • Doppler USS subclavian + vertebral arteries. • CT / MR angiography. • Catheter angiography (gold standard, also therapeutic).