Nonbacterial Thrombotic Endocarditis of Bioprosthetic Aortic Valve Presenting as Cardioembolic Stroke in a Patient without Predisposing Systemic Disease.

Nonbacterial thrombotic endocarditis (NBTE) describes a cluster of noninfectious heart valve lesions and is histologically characterised by the presence of sterile platelet and fibrin-rich aggregates. Risk factors include hypercoagulable states such as active malignancy, autoimmune disorders, and prothrombotic haematological conditions. NBTE involving bioprosthetic heart valves is exceedingly rare. We present a case of a 73-year-old man with a bioprosthetic aortic valve and no NBTE risk factors who developed right-sided homonymous hemianopia during an admission for decompensated congestive cardiac failure. After detailed clinical work-up including brain MRI, the man was diagnosed with acute ischemic cardioembolic stroke involving the left posterior cerebral artery territory. He subsequently underwent successful bioprosthetic aortic valve replacement with histologic examination of the explant supporting diagnosis of NBTE. Evidence of new neurological deficit or disturbance in patients with prosthetic heart valves should prompt investigation for cardioembolic stroke. Whilst rare, NBTE should be considered as a differential diagnosis for cardioembolic stroke, even in patients without predisposing systemic disease.