Ten-year pathological study of Beall mitral valve prostheses.

Detailed pathological studies are reported on 20 cloth-covered Beall mitral valve prostheses, which had to be removed for valve failure nine months to 10 years after implantation. Results in all patients except one indicated that there was a progressive and persistent granulomatous reaction that continued up to at least 10 years. Although the rate of tissue ingrowth into the valve decreased with time, the total volume of tissue formation increased. Cloth wear and disruption and deformity of the teflon discs was frequently seen. In these 20 valves the desired result--namely, the complete and smooth endothelialisation of the prosthesis--was certainly not achieved.