Chaim Sheba Medical Center, Tel Hashomer, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
J Am Coll Cardiol. 2012 Jan 10;59(2):119-27. doi: 10.1016/j.jacc.2011.09.045.
The purpose of this study was to assess deformation dynamics and in vivo mechanical properties of the aortic annulus throughout the cardiac cycle.
Understanding dynamic aspects of functional aortic valve anatomy is important for beating-heart transcatheter aortic valve implantation.
Thirty-five patients with aortic stenosis and 11 normal subjects underwent 256-slice computed tomography. The aortic annulus plane was reconstructed in 10% increments over the cardiac cycle. For each phase, minimum diameter, ellipticity index, cross-sectional area (CSA), and perimeter (Perim) were measured. In a subset of 10 patients, Young's elastic module was calculated from the stress-strain relationship of the annulus.
In both subjects with normal and with calcified aortic valves, minimum diameter increased in systole (12.3 ± 7.3% and 9.8 ± 3.4%, respectively; p < 0.001), and ellipticity index decreased (12.7 ± 8.8% and 10.3 ± 2.7%, respectively; p < 0.001). The CSA increased by 11.2 ± 5.4% and 6.2 ± 4.8%, respectively (p < 0.001). Perim increase was negligible in patients with calcified valves (0.56 ± 0.85%; p < 0.001) and small even in normal subjects (2.2 ± 2.2%; p = 0.01). Accordingly, relative percentage differences between maximum and minimum values were significantly smallest for Perim compared with all other parameters. Young's modulus was calculated as 22.6 ± 9.2 MPa in patients and 13.8 ± 6.4 MPa in normal subjects.
The aortic annulus, generally elliptic, assumes a more round shape in systole, thus increasing CSA without substantial change in perimeter. Perimeter changes are negligible in patients with calcified valves, because tissue properties allow very little expansion. Aortic annulus perimeter appears therefore ideally suited for accurate sizing in transcatheter aortic valve implantation.
本研究旨在评估整个心动周期主动脉瓣环的变形动力学和体内力学特性。
了解功能性主动脉瓣解剖的动态方面对于心脏不停跳经导管主动脉瓣植入术至关重要。
35 例主动脉瓣狭窄患者和 11 例正常对照者接受 256 层 CT 检查。在心动周期中，以 10%的增量重建主动脉瓣环平面。对于每个相位，测量最小直径、椭圆率指数、横截面积（CSA）和周长（Perim）。在 10 例患者的亚组中，通过主动脉瓣环的应力-应变关系计算杨氏弹性模量。
在正常和钙化主动脉瓣患者中，最小直径在收缩期均增加（分别为 12.3±7.3%和 9.8±3.4%；p<0.001），椭圆率指数降低（分别为 12.7±8.8%和 10.3±2.7%；p<0.001）。CSA 分别增加 11.2±5.4%和 6.2±4.8%（p<0.001）。钙化瓣膜患者的周长增加可忽略不计（0.56±0.85%；p<0.001），即使在正常患者中也很小（2.2±2.2%；p=0.01）。因此，与其他所有参数相比，最大和最小之间的相对百分比差异最小的是 Perim。患者的杨氏模量为 22.6±9.2 MPa，正常患者为 13.8±6.4 MPa。
主动脉瓣环通常呈椭圆形，在收缩期呈更圆的形状，从而增加 CSA，而周长变化不大。钙化瓣膜患者的周长变化可忽略不计，因为组织特性允许很小的扩张。因此，主动脉瓣环周长似乎非常适合经导管主动脉瓣植入术中的精确测量。
