<prompt> Commonest part of subclavian artery to be affected by stenosis is:First partSecond partThird partEqually affected  <response>: MC site of subclavian artery stenosis is the first part of the subclavian artery. MC cause of subclavian artery stenosis: Atherosclerotic disease Left subclavian artery stenosis is significantly more common than right MC site of stenosis: First part of the subclavian artery Stenosis typically occurs just distal to the origin of the subclavian artery and lies proximal to the origin of the vertebral artery. Stenosis of the first part of the subclavian artery may give rise to the subclavian steal syndrome Subclavian steal syndrome is characterized by reversed flow in the vertebral artery to compensate for a proximal stenosis in the ipsilateral subclavian artery there by stealing blood from the brain to feed the arm. 