Dynamic Hemodynamic Energy Loss in Normal and Stenosed Aortic Valves
Dynamic Hemodynamic Energy Loss in Normal and Stenosed Aortic Valves
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DOI：
10.1115/1.4000874
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发表时间：
2010-02-01
影响因子：
1.7
通讯作者：
Yoganathan, Ajit P.
中科院分区：
文献类型：
--
作者：
Yap, Choon-Hwai;Dasi, Lakshmi P.;Yoganathan, Ajit P.
主动脉瓣（AV）狭窄，如果不治疗，会导致心力衰竭。从力学的角度来看，心力衰竭可以解释为心脏无法产生足够的能量来克服循环中的能量损失。因此，用于评估AV性能和疾病严重程度的基于能量效率的测量具有作为AV流体动力学特性对心力衰竭的贡献的直接测量的优点。通过修正Navier-Stokes动量方程，提出了一种计算能量耗散率随收缩时间变化的新方法。该方法保留了Navier-Stokes动量方程的动力学项，并允许调查能量耗散率随时间的变化趋势。该方法适用于一系列体外实验，其中修剪的猪瓣膜暴露于各种条件：固定心率下的不同心搏量（50 ml至90 ml）;固定心搏量下的不同心率（60-80次/min）;以及不同狭窄水平（正常、轻度狭窄、中度狭窄）。其结果是：（1）由于在减速阶段期间的流动不稳定性，能量耗散波形具有向晚期收缩偏斜的独特模式：（2）增加心率和心搏量增加能量耗散，但是能量耗散波形的归一化形状在心率和心搏量上保持不变;（3）增加狭窄水平增加能量耗散，并且还改变能量耗散波形的归一化形状。由于狭窄会产生特征性能量耗散波形，因此动态能量耗散分析可能会扩展为AV评价的临床工具。[DOI：10.1115/1.4000874]
Aortic valve (AV) stenosis, if untreated, leads to heart failure. From a mechanics stand. point, heart failure can be interpreted as the failure of the heart to generate sufficient power to overcome energy losses in the circulation. Thus, energy efficiency-based measures for evaluating AV performance and disease severity have the advantage of being a direct measure of the contribution of the AV hydrodynamic characteristics toward heart failure. We present a new method for computing the rate of energy dissipation as a function of systolic time, by, modifying the Navier-Stokes momentum equation. This method preserves the dynamic term of the Navier-Stokes momentum equation, and allows the investigation of the trend of the rate of energy dissipation over time. This method is applied to a series of in vitro experiments, where a trimmed porcine valve is exposed to various conditions: varying stroke volumes (50 ml to 90 ml) at the fixed heart rate; varying heart rates (60-80 beats/min) at fixed stroke volume; and varying stenosis levels (normal, mild stenosis, moderate stenosis). The results are: (1) energy dissipation waveform has a distinctive pattern of being skewed toward late systole, due to flow instabilities during deceleration phases: (2) increasing heart rate and stroke volume increases energy, dissipation, but the normalized shape of the energy dissipation waveform is preserved across heart rates and stroke volumes; (3) increasing stenosis level increases energy dissipation, and also alters the normalized shape of the energy dissipation waveform. Since stenosis produces a signature energy dissipation waveform shape, dynamic energy dissipation analysis can potentially be extended into a clinical tool for AV evaluation. [DOI: 10.1115/1.4000874]