School of Life Science and BioEngineering, Beijing University of Technology, Beijing, 100124, People's Republic of China.
Med Biol Eng Comput. 2019 Dec;57(12):2657-2671. doi: 10.1007/s11517-019-02058-y. Epub 2019 Nov 10.
As the alternative treatment for heart failure, left ventricular assist devices (LVADs) have been widely applied to clinical practice. However, the effects of the support modes of LVADs on the biomechanical states of the aortic valve are still poorly understood. Hence, the present study investigates such effects and proposes a novel fluid-structure interaction (FSI) approach that combines the lattice Boltzmann method (LBM) and finite element (FE) method. Two support modes of LVADs, namely constant speed mode and constant flow mode, which have been widely applied to clinical practice, are also designed. Results demonstrate that the support modes of LVADs could significantly affect the biomechanical states of the aortic valve and the blood flow pattern of the ascending aorta. Compared with those in the constant flow mode, the leaflets in the constant speed mode could achieve better dynamic performance and lower stress during the systolic phase. The max radial displacement of the leaflets in the constant speed mode is at 8 mm, whereas that in the constant flow mode is at 0.8 mm. Furthermore, the outflow of LVADs directly impacts the aortic surfaces of the leaflets during the diastolic phase by increasing the level of wall shear stress of the leaflets. The leaflets in the constant speed mode receive less impact than those in the constant flow mode. The condition with such minimal impact is conducive to maintaining the normal structure of leaflets and benefits the reduction of the risk of valvular diseases. In sum, the support modes of LVADs exert a crucial effect on the biomechanical environment of the aortic valve. The constant speed mode is better than the constant flow mode in terms of providing a good hemodynamic environment for the aortic valve.
作为心力衰竭的替代治疗方法，左心室辅助装置（LVAD）已广泛应用于临床实践。然而，LVAD 的支持模式对主动脉瓣生物力学状态的影响仍知之甚少。因此，本研究探讨了这种影响，并提出了一种新的流固耦合（FSI）方法，该方法结合了格子玻尔兹曼方法（LBM）和有限元（FE）方法。还设计了 LVAD 两种广泛应用于临床的支持模式，即恒速模式和恒流模式。结果表明，LVAD 的支持模式会显著影响主动脉瓣的生物力学状态和升主动脉的血流模式。与恒流模式相比，恒速模式的瓣叶在收缩期具有更好的动态性能和更低的应力。恒速模式下瓣叶的最大径向位移为 8mm，而恒流模式下为 0.8mm。此外，LVAD 的流出在舒张期直接通过增加瓣叶壁面切应力水平对瓣叶的主动脉面产生影响。恒速模式下的瓣叶受到的冲击比恒流模式下的瓣叶小。这种最小冲击的情况有利于维持瓣叶的正常结构，有利于降低瓣膜疾病的风险。总之，LVAD 的支持模式对主动脉瓣的生物力学环境有重要影响。就为主动脉瓣提供良好的血液动力学环境而言，恒速模式优于恒流模式。
