A surgical case of prosthetic valve endocarditis with a difficult diagnosis.

Early diagnosis and treatment of prosthetic valve endocarditis (PVE) is important because it has a high mortality rate. We report a case of PVE which was difficult to diagnose. A 36-year-old man, who had undergone an aortic valve replacement (AVR) 7 years prior, was hospitalized with a high fever of unknown origin. We could not detect a stuck valve, vegetations or abscesses using echocardiography, and the peak aortic transvalvular pressure gradient had increased to 81 mmHg. We suspected PVE and initiated intravenous antibiotic therapy immediately. On day 5, echocardiography demonstrated an abnormal shadow directly under the prosthesis, and we definitively diagnosed PVE and performed an operation. Intraoperatively, the prosthesis was not vegetative, but the left ventricular outflow tract was filled with vegetation that was nearly obstructing it. After dissecting the infectious focus, we performed a re-AVR. Postoperative echocardiography showed that the peak left ventricular aortic pressure gradient decreased to 30 mmHg. Obstructive vegetation is difficult to diagnose by preoperative echocardiography.