Unexplained arterial thrombosis: approach to diagnosis and treatment.

Arterial thrombotic events in younger patients without a readily apparent etiology present significant diagnostic and management challenges. We present a structured approach to diagnosis with consideration of common causes, including atherosclerosis and embolism, as well as uncommon causes, including medications and substances, vascular and anatomic abnormalities, systemic disorders, and thrombophilias. We highlight areas of management that have evolved within the past 5 years, including the use of dual-pathway inhibition in atherosclerotic disease, antithrombotic therapy selection in embolic stroke of undetermined source and left ventricular thrombus, the role of closure of patent foramen ovale for secondary stroke prevention, and the thrombotic potential of coronavirus disease 2019 infection and vaccination. We conclude with a representative case to illustrate the application of the diagnostic framework and discuss the importance of consideration of bleeding risk and patient preference in determining the appropriate management plan.