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[Hemodynamic performance of newly developed composite stentless porcine aortic valve: in vitro testing and in vivo experiment with sheep].

OBJECTIVE
To investigate the effects of a newly developed composite stentless porcine aortic valve constructed from noncoronary leaflets of three porcine aortic valves.


METHODS
Fresh porcine hearts with ascending aorta were obtained from a slaughterhouse. The porcine aortic roots with ascending aorta and anterior leaflet of mitral valve and partial ventricular septum were dissected out and were pressurized to maintain their natural anatomical shapes with the leaflets floating freely at zero-pressure. Three noncoronary leaflets fixed in 0.6% glutaraldehyde were carefully matched for size and symmetry to construct a novel composite stentless porcine aortic valve. The lower margin and outside of the valve was covered with a piece of bovine pericardium. The novel stentless valves were tested in vitro pulsatile flow to detect the effective orifice area (EOA) and mean pressure difference (DeltaP) of the valve compared with the stented bovine pericardial bioprostheses of the same size. Sixteen male juvenile sheep underwent implantation of the novel valves in the supra-annular position in under cardio-pulmonary bypass. The intraoperative and postoperative echocardiography and pathological specimen were given to evaluate the hemodynamic performance and observed in the respects of a long-term survival, function of valve and pathological specimen.


RESULTS
Since novel valves had the unfavorable muscle-based right coronary leaflet characteristic of porcine valve removed it had larger EOA. Pulsatile flow testing indicated that the EOA of the 3 novel valves was (3.47 +/- 0.15), (3.69 +/- 0.11), and (3.92 +/- 0.18) cm2 respectively, all significantly greater than those of the stented bovine pericardial bioprosthesis [(2.00 +/- 0.16), (2.21 +/- 0.26), and (2.37 +/- 0.42) cm2 respectively] at each integral simulated cardiac output between 3 - 6 L/min (all P < 0.05), while the DeltaP levels of the novel valves were (2.35 +/- 0.41), (3.10 +/- 0.20), and (3.56 +/- 0.16) mm Hg respectively, all significantly lower than those of the stented bovine pericardial bioprosthesis [(4.98 +/- 0.46), (6.82 +/- 1.27), and (8.40 +/- 1.83) mm Hg respectively, all P < 0.05]. Twelve of the sixteen sheep survived after operation. Five of them had lived for more than 90 days, 3 more than 180 days, and 2 more than 360 days. The intra-operative echocardiographic analyses showed low DeltaP [(3.90 +/- 0.78) mm Hg] and no regurgitation in all sheep. After 15 to 360 days, all valves performed excellently. The sheep were postoperatively sacrificed in 5 d, 15 d, 45 d, 90 d, 180 d, or 300 d respectively. Necropsy revealed the valves had a low to mild level of calcification, without periprosthetic leakage and overgrowth of fibrous tissue.


CONCLUSION
The newly developed composite stentless porcine aortic valves show excellent hemodynamic performance with lower transvalvular pressure gradient and are relatively easy to implant.