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 degrees to 70 degrees 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 mu g Ca/mg (n = 8) versus 239.9 +/- 2.9 mu g Ca/mg (n = 8); bovine pericardium: 19.5 +/- 8 mu g Ca/mg (n = 6) versus 108 +/- 10.3 mu g 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. (C) 1998 by The Society of Thoracic Surgeons.