Coronary subclavian steal syndrome is the diversion of blood from the coronary circulation to the exercising left upper limb after a coronary artery bypass graft (CABG) using left internal mammary artery . This occurs when there is a high grade stenosis or occlusion of left subclavian artery proximal to the origin of the left internal mammary artery (LIMA). Though it is a rare phenomenon, it is a serious threat to the success of CABG.
Cardiovascular manifestation of coronary subclavian steal syndrome could be angina, myocardial infarction, malignant arrhythmias or heart failure . Cerebral symptoms can occur due to steal from the cerebral circulation through the vertebral artery. Angiographic prevalence of proximal left subclavian artery stenosis was 3.5% in a study of 492 patients . In that study, the prevalence was 5.3% in those with potential need for coronary artery bypass grafting. Peripheral arterial disease was a predictor of subclavian stenosis. A difference in blood pressure between the two upper limbs had a good specificity, but poor sensitivity for predicting left subclavian artery stenosis. Authors of the study suggested that left subclavian angiography should be done in surgical coronary artery disease patients if there was a blood pressure differential >10 mm Hg or evidence of peripheral arterial disease.
Exercise stress test by hand grip of the left hand is a useful test to document coronary subclavian steal syndrome . Awareness of coronary subclavian steal syndrome in post CABG patients is important as the clinical presentation can be variable. It causes a functional graft failure due to hemodynamically significant proximal subclavian artery stenosis .
Screening for subclavian stenosis by checking blood pressures in both arm has been recommended prior to CABG. Percutaneous revascularization prior to CABG has been advised in case subclavian stenosis is detected preoperatively. Good resolution of symptoms can be obtained in coronary subclavian steal syndrome by either surgical or percutaneous revascularization. Long term patency with either method has been reported to be excellent .
Retrograde flow through LIMA from left anterior descending coronary artery (LAD) has been demonstrated in a patient presenting with new ST elevation anterior wall myocardial infarction 12 years after CABG . The patient had critical stenosis at the LIMA-to-LAD anastomosis site and total occlusion at the origin of left subclavian artery. After primary percutaneous coronary intervention to the LIMA-to-LAD anastomotic site, antegrade flow from proximal to distal LAD was restored along with a preserved retrograde flow through the LIMA graft to left subclavian artery.
A series of 31 patients who underwent percutaneous transluminal angioplasty of left subclavian artery shortly before or after coronary artery bypass grafting with the use of LIMA has been reported . Thus subclavian angioplasty can be done either for prevention or treatment of coronary subclavian steal syndrome.