Kalejs Martins, Stradins Peteris, Lacis Romans, Ozolanta Iveta, Pavars Janis, Kasyanov Vladimir
Center of Cardiac Surgery, Pauls Stradins Clinical University Hospital, 13 Pilsonu Street, LV-1002 Riga, Latvia.
Interact Cardiovasc Thorac Surg. 2009 May;8(5):553-6. doi: 10.1510/icvts.2008.196220. Epub 2009 Feb 3.
The major problem with heart valve bioprostheses made from chemically treated porcine aortic valves is their limited longevity caused by gradual deterioration, which has a causal link with valve tissue mechanical properties. To our best knowledge, there are no published studies on the mechanical properties of modern, commercially available bioprostheses comparing them to native human valves. The objective of this study is to determine the mechanical properties of St Jude Epic bioprostheses and to compare them with native human and porcine aortic valves.
Leaflets from eight porcine aortic valves and six Epic bioprostheses were analyzed using uni-axial tensile tests in radial and circumferential directions. Mechanical properties of human valves have been previously published by our group. Results are represented as mean values+/-S.D.
Circumferential direction. Modulus of elasticity of Epic bioprostheses in circumferential direction at the level of stress 1.0 MPa is 101.99+/-58.24 MPa, 42.3+/-4.96 MPa for native porcine and 15.34+/-3.84 MPa for human aortic valves. Ultimate stress is highest for Epic bioprostheses 5.77+/-1.94 MPa, human valves have ultimate stress of 1.74+/-0.29 MPa and porcine 1.58+/-0.26 MPa. Ultimate strain in circumferential direction is highest for human valves 18.35+/-7.61% followed by 7.26+/-0.69% for porcine valves and 5.95+/-1.54% for Epic bioprostheses. Radial direction. Modulus of elasticity in radial direction is 9.18+/-1.81 MPa for Epic bioprostheses, 5.33+/-0.61 MPa for native porcine, and 1.98+/-0.15 MPa for human aortic valve leaflets. In the radial direction ultimate stress is highest for Epic bioprostheses 0.7+/-0.21 MPa followed by native porcine valves 0.55+/-0.11 MPa and 0.32+/-0.04 MPa for human valves. For human valves ultimate strain is 23.92+/-4.87%, for native porcine valves 8.57+/-0.8% and 7.92+/-1.74% for Epic bioprostheses.
Epic bioprostheses have non-linear stress-strain behavior similar to native valve tissue, but they are significantly stiffer and hence less elastic compared to native porcine and human aortic valves. These differences in mechanical properties may cause variations in stress distribution within leaflets of the bioprosthetic valves and accelerate their deterioration.
由化学处理的猪主动脉瓣制成的心脏瓣膜生物假体的主要问题是其因逐渐退化导致的寿命有限，这与瓣膜组织的机械性能存在因果关系。据我们所知，尚无已发表的研究对现代市售生物假体与天然人体瓣膜的机械性能进行比较。本研究的目的是确定圣犹达Epic生物假体的机械性能，并将其与天然人体和猪主动脉瓣进行比较。
对八个猪主动脉瓣和六个Epic生物假体的瓣叶在径向和周向进行单轴拉伸试验分析。我们团队之前已发表过人体瓣膜的机械性能。结果以平均值±标准差表示。
周向。Epic生物假体在应力1.0MPa水平下的周向弹性模量为101.99±58.24MPa，天然猪主动脉瓣为42.3±4.96MPa，人体主动脉瓣为15.34±3.84MPa。Epic生物假体的极限应力最高，为5.77±1.94MPa，人体瓣膜的极限应力为1.74±0.29MPa，猪主动脉瓣为1.58±0.26MPa。周向极限应变在人体瓣膜中最高，为18.35±7.61%，其次是猪瓣膜的7.26±0.69%和Epic生物假体的5.95±1.54%。径向。Epic生物假体的径向弹性模量为9.18±1.81MPa，天然猪主动脉瓣为5.33±0.61MPa，人体主动脉瓣瓣叶为1.98±0.15MPa。在径向，Epic生物假体的极限应力最高，为0.7±0.21MPa，其次是天然猪瓣膜的0.55±0.11MPa和人体瓣膜的0.32±0.04MPa。人体瓣膜的极限应变为23.92±4.87%，天然猪瓣膜为8.57±0.8%，Epic生物假体为7.92±1.74%。
Epic生物假体具有与天然瓣膜组织相似的非线性应力-应变行为，但与天然猪主动脉瓣和人体主动脉瓣相比，其刚度明显更高，因此弹性更小。这些机械性能的差异可能导致生物假体瓣膜瓣叶内应力分布的变化，并加速其退化。
