Degeneration in porcine bioprosthetic cardiac valves: incidence of primary tissue failures among 938 bioprostheses at risk.

From June 1974 through December 1980, 938 porcine xenografts were inserted in 794 selected patients who survived surgery and who were considered at risk for primary tissue valve failure. Sixty-three instances of primary tissue valve degeneration occurred in 59 of the 794 patients. In patients operated on 9 years ago, 29% of the valves implanted in the mitral position (5 of 17) and 27% in the aortic position (3 of 11) failed. These percentages decreased to 18% (14 of 80) and 20% (11 of 54) for those implanted in 1975, 8% (6 of 73) and 14% (7 of 51) for those implanted in 1976, 9% (6 of 68) and 5% (4 of 76) for 1977, and 4% (3 of 79) and 3% (2 of 63) for 1978. The average interval between valve placement and explantation or death was 56 months (range 10 to 98) for valves in the mitral position and 68 months (range 12 to 92) for valves in the aortic position. The rate of valve survival without degeneration was 98 +/- 1% at 4 years, 96 +/- 2% at 5 years, 90 +/- 3% at 6 years, 87 +/- 4% at 7 years and 76 +/- 7% at 8 and 9 years. Until 1978, 4 valves failed, 8 failed in 1979 to 1980, 12 in 1981, 25 in 1982, and 14 have already failed from January to May 1983. Our figures show a progressive increase in valve degeneration with the passing of time. No leveling of this failure rate has so far been observed.