Babin-Ebell Joerg, Sievers Hans H, Misfeld Martin, Runge Maike, Vogt Paul Robert, Scharfschwerdt Michael
Department of Cardiac Surgery, University Clinic of Schleswig-Holstein, Lübeck, Germany.
J Heart Valve Dis. 2008 Sep;17(5):566-70.
Although, in small aortic annulus or aortic annulus calcification, it is recommended that valves are implanted in a tilted position, mechanical valves show impaired hemodynamic performance when positioned in this way. To date, no investigations have been conducted with biological valves implanted in a tilted position.
Measurements were performed in a pulsatile flow simulator. The aortic roots were mounted in a fluid reservoir and tested with bioprosthetic valves implanted in the regular position (21 mm; n = 7) or at a 200 tilt (23 mm; n = 7). Additional 21 mm valves were implanted in both positions with a systemic pressure of 120/80 mmHg. Subsequently, the valves were implanted into a glass model and flow visualization monitored by adding air bubbles illuminated with a laser diode.
The 21 mm valves showed a slightly higher transvalvular gradient in the tilted than in the regular position, while 23 mm valves in a tilted position showed a lower gradient than 21 mm valves in the regular position. Flow in the regular position was seen to be straight and central, but in the tilted position was diverted and impacted on the aortic wall. Vortex formation in the tilted position was more pronounced than in the regular position, with certain low-flow areas being observed.
The implantation of a one size-larger bioprosthetic valve at a 20 degree tilt in a small aortic root resulted in a slight reduction in transvalvular gradient compared to a smaller valve implanted in the regular position. Whilst mechanical valve performance is markedly compromised in the tilted position, the bioprosthetic valve showed only minor impairment of transvalvular pressure gradient due to tilting, and this was overcompensated by the larger valve size. However, the advantage of a greater orifice area must be traded against the consequences of the observed flow disturbances.
尽管对于小主动脉瓣环或主动脉瓣环钙化的情况，建议将瓣膜倾斜植入，但机械瓣膜以这种方式放置时血流动力学性能会受损。迄今为止，尚未对倾斜植入生物瓣膜进行过研究。
在脉动流模拟器中进行测量。将主动脉根部安装在储液器中，并用植入正常位置（21毫米；n = 7）或倾斜20°（23毫米；n = 7）的生物瓣膜进行测试。另外，在两种位置植入21毫米瓣膜，并将系统压力设定为120/80 mmHg。随后，将瓣膜植入玻璃模型中，并通过添加由激光二极管照亮的气泡来监测血流可视化情况。
21毫米瓣膜在倾斜位置的跨瓣压差略高于正常位置，而倾斜位置的23毫米瓣膜跨瓣压差低于正常位置的21毫米瓣膜。正常位置的血流是直的且位于中心，但在倾斜位置血流发生转向并冲击主动脉壁。倾斜位置的涡流形成比正常位置更明显，且观察到了某些低流量区域。
与正常位置植入较小瓣膜相比，在小主动脉根部以20度倾斜植入大一号的生物瓣膜会使跨瓣压差略有降低。虽然机械瓣膜在倾斜位置的性能明显受损，但生物瓣膜因倾斜导致的跨瓣压力梯度仅轻微受损，且这种受损被更大的瓣膜尺寸所弥补。然而，更大的瓣口面积优势必须与观察到的血流紊乱后果相权衡。
