Stump-related embolism from a thrombosed carotid–subclavian bypass causing large vessel occlusion after thoracic endovascular aortic repair

Background: Kommerell diverticulum frequently requires thoracic endovascular aortic repair (TEVAR) with carotid–subclavian bypass (CSB). Although CSB is durable, delayed embolic stroke secondary to graft failure is rare. We report a rare case of large vessel occlusion caused by a stump-related embolism from an occluded CSB. Case Description: A 34-year-old man with a history of deep vein thrombosis under warfarin therapy developed right hemiplegia and aphasia 85 days after TEVAR and left CSB for Kommerell diverticulum. Upon admission, physical examination revealed a marked inter-arm blood pressure difference (40-mmHg drop in the left arm). Initial laboratory testing showed a subtherapeutic international normalized ratio of 1.7. Magnetic resonance imaging demonstrated left internal carotid artery terminus occlusion. Angiography revealed complete occlusion of the CSB with a 2-cm blind-ended stump distal to the carotid anastomosis, showing significant contrast stagnation. Mechanical thrombectomy achieved complete reperfusion. Strict antithrombotic management prevented recurrence. Conclusion: A thrombosed CSB can act as a dangerous embolic source through a mechanism analogous to carotid stump syndrome. Careful long-term vascular surveillance and bedside monitoring of inter-arm blood pressure differences are vital for early detection of graft dysfunction.