Fate of a second porcine bioprosthetic valve.

Since October, 1971, 744 porcine bioprosthetic valves were inserted in patients discharged from the hospital and were therefore at risk for primary valve failure or tissue degeneration. In this period of time, 41 valves have demonstrated spontaneous degeneration. The percentages of valve survival without degeneration are as follows: at 6 yeras, 93% +/- 1.5% (SE); 7 years, 88% +/- 2.0%; 8 years, 82% +/- 2.9%; 9 years, 80% +/- 3.4%. The incidence of degeneration appears to be decreasing even though the total number of valves at risk is increasing each year. Of the 41 valves removed for spontaneous degeneration, 25 valves in 24 patients have been replaced by a second bioprosthesis. These 24 patients have been followed up for from 2 to 61 months, and there has been no clinical evidence of degeneration of the second bioprosthesis. One patient has had a second bioprosthesis longer than the first. Although others have suggested that degeneration may be immunologic event, our experience suggests that there is no "second set" rejection. The absence of a "second set" rejection and the suggestion of a decreasing incidence of degeneration makes us continue to favor the bioprosthesis for primary and secondary valve replacement.