Heat treatment mitigates calcification of valvular bioprostheses

Background. Several techniques have been proposed to mitigate calcification of glutaraldehyde-preserved bioprostheses. None has been fully satisfactory. Knowing that heat induces significant molecular changes, we investigated the potential benefit of the heat treatment of glutaraldehyde-fixed tissues. Methods. Samples of porcine valves and bovine pericardium treated in 0.625% glutaraldehyde were submitted to temperatures from 37° to 70°C for 2 to 12 weeks and then implanted subcutaneously in newborn rats for 3 months. In a second protocol, nine heat-treated porcine valve bioprostheses and seven control porcine valve bioprostheses were implanted in the mitral position in sheep for 20 weeks. Results. Spectrophotometry and x-ray analysis comparing heat-treated versus non–heat-treated tissues showed the following: porcine valve: 6.7 ± 2.3 μg Ca/mg (n = 8) versus 239.9 ± 2.9 μg Ca/mg (n = 8); bovine pericardium: 19.5 ± 8 μg Ca/mg (n = 6) versus 108 ± 10.3 μg Ca/mg (n = 8); and porcine valve bioprostheses: 0 versus ++. Conclusions. Heat treatment of glutaraldehyde-treated bioprostheses significantly mitigated calcification in both subcutaneous and mitral position.