Pathophysiology: Luminal obstruction in the proximal left subclavian artery results in the reverse of blood flow in the left internal mammary artery, robbing the heart and sometimes brain to supply the left upper extremity.
Clinical features of the coronary-subclavian steal syndrome:
(1) history of bypass graft between the left internal mammary artery and a coronary artery
(2) systolic blood pressure difference in the upper extremities, with right blood pressure >= left + 20 mm Hg
(3) bruits over the left subclavian and/or left carotid artery(ies)
(4) combination of dizziness and angina pectoris
(5) cerebrovascular symptoms
The cerebrovascular symptoms are caused by either:
(1) embolization of plaque to the left vertebral artery
(2) steal from the left vertebral artery
Diagnosis is based on imaging studies of the left subclavian artery. This will demonstrate moderate to severe atherosclerosis in the proximal left subclavian artery prior to the origins of the left vertebral and left internal mammary arteries. Coronary angiography will demonstrate retrograde flow in the left internal mammary artery.
