Case Presentation: A 64 year old female with a past medical history of coronary artery disease and coronary artery bypass graft, heart failure with reduced ejection fraction, diabetes mellitus, peripheral arterial disease, hyperlipidemia and a strong smoking history presented to the emergency department with exertional dyspnea worsening over the past 1 month and substernal chest pressure developing acutely on day of presentation. EKG showed atypical RBBB and nonspecific T wave abnormalities in anterior leads with normal Troponin T (<0.01 ng/mL) and mildly elevated proBNP (531 pg/mL). Stress EKG did not show any evidence of inducible ischemia, but perfusion scan detected very large areas of partially reversible ischemia in the inferior and inferolateral walls with stress-induced moderate-to-severe global left ventricular systolic dysfunction and inducible wall motion abnormality. Cardiac catheterization was performed which showed patency of the saphenous vein graft (SVG) and left internal mammary artery (LIMA) graft but detected retrograde flow from the left anterior descending artery to LIMA and a 90% in-stent restenosis of the subclavian artery. Of note the patient had a history of coronary-subclavian steal phenomenon in 2013 which was treated with a left subclavian bare metal stent placement. After consulting vascular surgery, the subclavian artery was successfully re-stented, and patient was discharged the following day.

Discussion: Although the use of LIMA in bypassing the LAD has been well established and proven to be beneficial, this common procedure could lead to an underdiagnosed complication known as the coronary-subclavian steal syndrome (CSSS) which happens when there is a substantial occlusion of the subclavian artery proximal to the ostia of LIMA, causing blood to backflow from the LIMA to the subclavian to maintain left upper extremity perfusion, specially at times of exertion.[1, 2]Coronary subclavian steal syndrome (CSSS) is a rare cause of chest pain in post-CABG patients where myocardial ischemia is due to retrograde blood flow from LIMA to the distal left subclavian artery secondary to occlusion in the proximal section of the left subclavian artery. Although this phenomenon is underdiagnosed, the most common cause of anginal chest pain in post-CABG patients is atherosclerotic disease of the native coronary arteries or the grafts.[3]Multiple causes have been explained for development of CSSS with subclavian artery stenosis secondary to atherosclerotic disease being the most common, and Takayasu arteritis, radiation arteritis and hemodialysis AV fistula being less common causes.[4]The timeframe of start of CSSS after CABG has been reported between 2 to 31 years. Subclavian artery calcification risk factors include advanced age, hypertension, diabetes mellitus, and smoking, and the highest incidence of subclavian artery stenosis has been detected in patients with peripheral arterial disease in other arteries.[5, 6]

Conclusions: Our patient had a recurrence of CSSS after in-stent restenosis of a previously stented left subclavian artery. Patient’s multiple risk factors including history of peripheral arterial disease, smoking history and diabetes mellitus are among the contributing factors resulting in recurrence of this phenomenon. Risk factor reduction and better control of other comorbid conditions along with routine follow-up can help prevent further episodes and prolong survival of such patients.