Carrel Thierry, Dembitsky Walter P, de Mol Bas, Obrist Dominik, Dreyfus Gilles, Meuris Bart, Vennemann Bernhard, Lapeyre Didier, Schaff Hartzell
Department for Cardiovascular Surgery, University Hospital and University of Bern, Switzerland.
Department for Cardiovascular Surgery, Sharp Memorial Hospital, San Diego, CA, USA.
Int J Cardiol. 2020 Apr 1;304:125-127. doi: 10.1016/j.ijcard.2020.01.056. Epub 2020 Jan 23.
Mechanical heart valve prostheses are based on older designs without changes during the last 40 years. Today, there is an unmet need for less thrombogenic mechanical prostheses. Analysis of the relationship between flow characteristics and thromboembolic complications is possible using numerical and biomolecular flow studies that have shown that the reverse rather than the forward flow is responsible for local platelet activation and thrombosis. After peak flow, leaflets experience flow deceleration and the leaflets are still widely open when the flow becomes zero. The closure of the valve starts with the onset of reverse flow. Therefore, the valve closes extremely fast with most of the leaflet traveling angle occurring in <10 ms with excessively high reverse flow velocities. The pivoting spaces, so-called "Hot Spots" should be eliminated to prevent pathologic shear stress that result in thrombosis. A novel tri-leaflet valve combines favorable hemodynamics with the durability of mechanical heart valve. This valve closes within 60 ms, much slower than bi-leaflet valves and similar to the closing mode of a tissue valve. Micro-particle image velocimetry did not show critical regions of flow stagnation and zones of excessive shear in the pivoting region suggesting low potential for thrombogenic events that should allow to avoid long-term anticoagulation.
机械心脏瓣膜假体基于过去40年未作改变的旧设计。如今，对血栓形成倾向较低的机械假体存在未满足的需求。利用数值和生物分子流动研究分析流动特性与血栓栓塞并发症之间的关系是可行的，这些研究表明，反向流动而非正向流动是导致局部血小板活化和血栓形成的原因。在峰值流量之后，瓣叶经历流动减速，当流量变为零时，瓣叶仍广泛打开。瓣膜的关闭始于反向流动的开始。因此，瓣膜关闭极快，大部分瓣叶行进角度发生在<10毫秒内，反向流速过高。应消除所谓的“热点”枢转空间，以防止导致血栓形成的病理性剪切应力。一种新型三叶瓣膜将良好的血流动力学与机械心脏瓣膜的耐用性相结合。该瓣膜在60毫秒内关闭，比双叶瓣膜慢得多，类似于组织瓣膜的关闭模式。微粒图像测速法未显示枢转区域存在流动停滞的关键区域和过度剪切区域，这表明血栓形成事件的可能性较低，应可避免长期抗凝。
