[Intermittent opening of a mechanical mitral valve prosthesis due to pannus formation; report of a case].

A 76-year-old woman with a history of severe mitral valve stenosis had undergone mitral valve replacement with a 27 mm St. Jude Medical (SJM) valve in 1991. Follow-up transthoracic echocardiography revealed an increase in the pressure gradient across the mitral prosthesis 16 years after the surgery. Prosthetic valve dysfunction was suspected, but transesophageal echocardiography and cineradiography failed to show mechanical valve dysfunction. Two years later, she presented with dyspnea on exertion and leg edema. Cineradiography revealed intermittent restriction of the opening of the mechanical valve leaflet approximately every 10 beats. Thus, we diagnosed intermittent prosthetic valve dysfunction and performed a reoperation. On inspection of the prosthesis, we observed semicircular pannus formation around the posterior leaflet in the ventricular side. It was considered that the pannus tissue had interfered with 1 leaflet opening of the mitral valve prosthesis, resulting in intermittent valve dysfunction. We replaced the prosthesis with a new 25 mm SJM valve. The patient was discharged after confirmation of normal prosthetic function.