Background: The current generation of prosthetic heart valves are excellent examples of engineering that work well, for long periods of time. Unfortunately, host-related problems and consequent valve failure continue to occur, including infective endocarditis. St Jude Medical Inc introduced a new model of mechanical heart valve prosthesis with silver-treated fabric to try to reduce the incidence of infective endocarditis. Two cases of failure of this prosthesis, with a clinical diagnosis of infective endocarditis, are presented.
Materials and methods: Of the 176 St Jude Medical Silzone-coated prostheses implanted, two were explanted in the first half of 1998. The clinical status of the patients was reviewed, and a detailed gross, histological and stereomicroscopic examination of the prosthetic valves was undertaken.
Results: Clinically, both patients developed symptoms of infective endocarditis. The first patient developed features of a stroke and two months later underwent a second valve replacement. The prosthesis showed pannus and thrombus. A paravalvular leak was revealed in the second patient, who underwent a second valve replacement six months after the initial surgery. Blood and tissue cultures were negative in both cases.
Conclusions: The new model St Jude Medical Silzone mechanical heart valve prosthesis, designed to prevent infective endocarditis, was associated with clinical features of endocarditis in these two cases. Significant pannus and thrombus were seen on both prostheses, which likely led to emboli and stroke in the first case. The cause of the paravalvular abscess in the second case has not yet been established. The early failure of these prostheses suggests that patients with this prosthesis be followed up carefully.