Kangxiong Liao

Intraoperative epicardial Echo/Doppler evaluation of a stentless, chordally supported quadricusp mitral bioprosthesis

The authors have developed a stentless, chordally supported quadricusp mitral bioprosthesis made from bovine pericardium. A large anterior, two commissural, and one posterior cusp all have straight hinge lines and avoid the excessive flexion stress of stent supported valves. The chordal support is concentrated in two flaps for suture to the papillary muscles. Previous in vitro and animal studies demonstrated its superior hemodynamic, biomechanical, and biocompatible behavior over commercial valve bioprostheses. In this study, we further evaluated its in vivo performance by intraoperative epicardial Echo/Doppler immediately after the bioprosthesis was implanted in 10 sheep. In all 10 sheep, Echo showed the valves were similar to native mitral valves in both anatomic appearance and movement. Mitral annular motion and annular-papillary muscle integrity were preserved. In systole, the valves closed competently with chordae moving upward and straightening; in diastole, the valves opened wide with chordae moving downward and relaxing. Color and pulsed Doppler showed no signs of stenosis or regurgitation. In conclusion, the new mitral bioprosthesis provide excellent in vivo performance that mimics the native mitral valve. Intraoperative echocardiography is recommended after mitral valve replacement with such valves.

Spontaneous host endothelial growth on bioprosthetic valves and its relation to calcification

We studied host endothelial growth and calcification of bovine pericardial valve prostheses treated with: (A) 0.625% glutaraldehyde + 4% formaldehyde, (B) 99.5% glycerol or (C) 99.5% glycerol + 4% formaldehyde. Twenty-three stentless chordally supported bileaflet pericardial mitral valves with treatments A (n = 6), B (n = 6) or C (n = 11) were implanted in juvenile sheep for 125-273 days. After sacrifice, the anterior cusp from the annulus to papillary muscle of each valve was examined by scanning electron microscopy for the presence of endothelial cells, and the intrinsic calcification of each valve was determined by measuring calcium (micrograms/mg dry weight) from another 1 cm2 piece of grossly normal cusp. Sixty pieces of 1 cm2 pericardium with treatment A, B or C (n = 20 in each group) were implanted in 30 rats for 70 days. Calcium analysis and histology study of the implants were performed. In sheep, within a similar range of implantation periods, the endothelial growth rate of the valves was the highest in group B, 100% (6/6); group C was 45.5% (5/11) and A 16.7% (1/6). There were no significant differences in calcium among groups A, B and C. In rat implants, the calcium of group B was much lower than that of A or C (B = 6.92 +/- 4.46 vs A = 144.52 +/- 27.66 or C = 240.54 +/- 13.47, P < 0.05) although its histology showed more severe degeneration and inflammatory changes. Pericardial mitral valves treated with glycerol show satisfactory biocompatibility with regard to host endothelial growth and prevention of calcification; however, these tissues show evidence of rapid degeneration.(ABSTRACT TRUNCATED AT 250 WORDS)