Intravascular Ultrasound (IVUS)-Guided Endovascular Treatment of Severe Left Subclavian Artery Stenosis in a Patient With High-Risk Post-Coronary Artery Bypass Grafting Surgery.

Coronary-subclavian steal syndrome (CSSS) is an uncommon but clinically important entity that may occur after coronary artery bypass grafting (CABG) with internal mammary artery conduits. Hemodynamically significant proximal left subclavian artery (LSA) stenosis can alter distal branch vessel flow and, in patients with prior left internal mammary artery (LIMA)-based CABG, may raise concern for coronary-subclavian steal physiology. Concurrent vertebral artery flow reversal may further predispose to cerebrovascular insufficiency. We report a case of a 75-year-old male with an extensive cardiovascular history, including prior CABG, transcatheter aortic valve replacement (TAVR), thoracic endovascular aortic repair (TEVAR), and a cardiac implantable electronic device, who presented with dizziness and was found to have severe proximal left subclavian artery stenosis. Computed tomography angiography demonstrated severe (~90%) proximal LSA stenosis, while duplex ultrasonography revealed alternating vertebral artery flow consistent with evolving steal physiology. Invasive hemodynamic assessment confirmed a significant trans-stenotic gradient (>25 mmHg). Given the patient's prior LIMA-based CABG, severe proximal LSA stenosis raised concern for possible coronary-subclavian steal physiology, although direct angiographic confirmation of retrograde LIMA flow was not available. The patient underwent a hybrid endovascular approach utilizing intravascular ultrasound (IVUS)-guided lesion assessment and optimization, drug-coated balloon (DCB) angioplasty, and precise deployment of a balloon-expandable covered stent (GORE VIABAHN VBX; Flagstaff, AZ: W. L. Gore & Associates). The procedure restored antegrade subclavian flow, normalized the trans-stenotic pressure gradient, and preserved the vertebral artery origin. This case demonstrates the technical feasibility of a multimodality endovascular approach for severe proximal LSA stenosis with evolving vertebrobasilar steal physiology in a high-risk post-CABG patient. Integration of IVUS guidance, DCB therapy, and covered stent technology may assist procedural optimization in carefully selected patients, although further studies are required to define the long-term role of this strategy in supra-aortic trunk disease.