Mechanical Thrombectomy for Acute Ischemic Stroke Caused by Prosthetic Aortic Valve Endocarditis Due to <i>Exophiala dermatitidis</i> Infection: A Case Report

Abstract

Prosthetic valve endocarditis (PVE) can cause large cerebral vessel occlusion. Many reports suggested that mechanical thrombectomy (MT) is effective and useful for early diagnosis from the histopathological findings of thrombus. We present the case of a 62-year-old man, with a history of prosthetic aortic valve replacement and pulmonary vein isolation for his atrial fibrillation, who developed a high fever and an acute neurological deficit, with left hemiplegia and speech disorder. He was diagnosed as having an acute right middle cerebral artery embolism and underwent an MT. The embolic source was found to be a PVE vegetation. However, histopathological analysis of the thrombus could not detect the actual diagnosis. Although he was treated for bacterial endocarditis, his blood culture revealed a rare fungal infection with Exophiala dermatitidis not until >3 weeks after admission. Subsequently, a ß-D-glucan assay also indicated elevated levels. Although he underwent an aortic valve replacement on day 36, MRI showed multiple minor embolic strokes till that day. Early diagnosis of fungal endocarditis and detection of the causative pathogen are still challenging, and the disease has a high risk of occurrence of early and repeated embolic stroke. In addition to clinical findings and pathological studies, ß-D-glucan assay might be a good tool for the diagnosis and evaluation of fungal endocarditis.

Exophiala dermatitidisfungal infective endocarditis on prosthetic mitral valve

“…The incidence of prosthetic valve endocarditis (PVE) in patients with prosthetic heart valves is 6/1000 annually, primarily due to Staphylococcus aureus and coagulase-negative staphylococci 1. Fungal infections merely account for 3–4% of PVE cases, yet have a high mortality rate of 40–90% 2–4. Candida and Aspergillus species are the most common fungi, while Exophiala dermatitidis , as in our case, has been rarely reported.…”

“…E. dermatitidis , colloquially termed ‘black yeast’ due to melanin in its cell wall, thrives in diverse environmental settings, including soil, decaying organic matter and synthetic indoor habitats 2 3. Its capacity to generate biofilms endows it with considerable virulence and potential for persistent infections.…”

“…The sensitivity of the modified Duke’s criteria for diagnosing fungal endocarditis is lower than for bacterial endocarditis, with only half of the fungal cases testing positive within 3 weeks of admission 2 4. Therefore, in patients with risk factors like prolonged catheter use, intravenous drug use, steroid therapy, organ transplants, cancer, cystic fibrosis, prosthetic valves and cardiac surgery, and fungal infection should be included in the initial diagnostic evaluation 2–6. Given the long incubation period for fungal cultures, non-culture-based tests like the 1–3-B-D-Glucan test, can be instrumental in early diagnosis, with high sensitivity and specificity of 77% and 85%, respectively 10…”

“…Current evidence is derived from case reports, without conclusive guidelines on optimal antifungal therapy and treatment duration. The systemic disease usually warrants a combination of prolonged antifungal therapy with novel compounds and azoles, along with surgical intervention 1–6. Optimal treatment strategies warrant further investigations.…”

“…Candida and Aspergillus species are the most common fungi, while Exophiala dermatitidis , as in our case, has been rarely reported. With just four cases reported involving the aortic valve in immunocompetent2 5, immunocompromised post-transplant,3 or patients using intravenous drugs6 ( Supplemental Table 1 ), our case represents the first report of a prosthetic mitral valve infection in an immunocompetent individual.…”