Coronary-Subclavian Steal Syndrome in a Post-Coronary Artery Bypass Grafting Patient: A Reversible Cause of Myocardial Ischemia.

BACKGROUND Coronary-subclavian steal syndrome (CSSS) is a rare but clinically significant cause of myocardial ischemia in patients with prior coronary artery bypass grafting (CABG), particularly when the left internal mammary artery (LIMA) is used as a conduit. Proximal subclavian artery stenosis can lead to reversal of LIMA graft flow, resulting in compromised myocardial perfusion that can mimic progression of native coronary disease. CASE REPORT A 63-year-old man with a history of multi-vessel coronary artery disease, prior PCI, and CABG with a LIMA-to-LAD graft presented with progressive exertional chest pain and left upper-extremity paresthesia. Physical examination revealed a diminished left radial pulse and inability to obtain blood pressure in the affected arm, raising suspicion for a proximal inflow lesion. CTA subsequently identified high-grade stenosis of the proximal left subclavian artery, and coronary angiography confirmed underfilling of the LIMA-LAD graft consistent with CSSS physiology. After evaluating medical therapy, redo surgical revascularization, and endovascular intervention, percutaneous stent placement was selected due to its lower procedural morbidity and favorable reported outcomes. A balloon-expandable stent was successfully deployed, restoring antegrade flow with immediate improvement in graft perfusion. CONCLUSIONS This case emphasizes the importance of recognizing coronary-subclavian steal syndrome in post-CABG patients presenting with recurrent angina and upper-extremity vascular findings. Targeted vascular imaging and bedside examination facilitated the diagnosis, and endovascular subclavian revascularization proved safe and effective in restoring graft perfusion. A practical diagnostic flowchart is also presented to support clinical evaluation and management in similar cases.