Floating aortic arch thrombus revealing an occult ascending aortic dissection: a case report.

Floating thrombus of the thoracic aorta is an uncommon but potentially catastrophic source of systemic embolization. Although most cases are associated with structural abnormalities of the aortic wall, pre-operative imaging may occasionally suggest an isolated intraluminal thrombus, with the underlying pathology becoming evident only during surgical exploration. We report the case of a 49-year-old woman with active tobacco use who presented with progressive pain and dysesthesia of the left upper limb and was diagnosed with brachial artery thrombosis. Computed tomography angiography revealed an intraluminal thrombus within the aortic arch, while echocardiography showed a large, highly mobile pedunculated mass attached to the lesser curvature. Given the high risk of recurrent embolization, urgent surgical intervention was performed. Intraoperative inspection identified a giant floating thrombus measuring approximately 8 cm. Further exploration revealed an ulcerated lesion with a contained dissection of the ascending aorta, considered the likely nidus for thrombus formation. The thrombus was removed, and the affected ascending aortic segment was resected and reconstructed using a supracoronary Dacron graft. The post-operative course was uneventful, and the patient was discharged on oral anticoagulation. This case highlights a key diagnostic limitation of pre-operative imaging and supports surgical exploration as both a diagnostic and therapeutic strategy in selected high-risk patients.