Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy; 3D and Computer Simulation Laboratory, IRCCS Policlinico San Donato, San Donato Milanese, Italy.
3D and Computer Simulation Laboratory, IRCCS Policlinico San Donato, San Donato Milanese, Italy; Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy.
J Biomech. 2021 Apr 15;119:110308. doi: 10.1016/j.jbiomech.2021.110308. Epub 2021 Feb 8.
Blood is generally modeled as a Newtonian fluid, assuming a standard and constant viscosity; however, this assumption may not hold for the highly pulsatile and recirculating intracavitary flow in the left ventricle (LV), hampering the quantification of fluid dynamic indices of potential clinical relevance. Herein, we investigated the effect of three viscosity models on the patient-specific quantification of LV blood energetics, namely on viscous energy loss (EL), from 4D Flow magnetic resonance imaging: I) Newtonian with standard viscosity (3.7 cP), II) Newtonian with subject-specific hematocrit-dependent viscosity, III) non-Newtonian accounting for the effect of hematocrit and shear rate. Analyses were performed on 5 controls and 5 patients with cardiac light-chain amyloidosis. In Model II, viscosity ranged between 3.0 (-19%) and 4.3 cP (+16%), mildly deviating from the standard value. In the non-Newtonian model, this effect was emphasized: viscosity ranged from 3.2 to 6.0 cP, deviating maximally from the standard value in low shear rate (i.e., <100 s) regions. This effect reflected on EL quantifications: in particular, as compared to Model I, Model III yielded markedly higher EL values (up to +40%) or markedly lower (down to -21%) for subjects with hematocrit higher than 39.5% and lower than 30%, respectively. Accounting for non-Newtonian blood behavior on a patient-specific basis may enhance the accuracy of intracardiac energetics assessment by 4D Flow, which may be explored as non-invasive index to discriminate between healthy and pathologic LV.
血液通常被建模为牛顿流体，假设其具有标准且恒定的粘度；然而，这一假设对于左心室（LV）中高度脉动和再循环的腔内流动可能不成立，这阻碍了对潜在临床相关的流体动力学指数的量化。在此，我们研究了三种粘度模型对 LV 血液能量特定量化的影响，即从 4D 流动磁共振成像上：I）牛顿，使用标准粘度（3.7 cP），II）牛顿，使用特定个体的与血球比容相关的粘度，III）考虑血球比容和剪切率影响的非牛顿。对 5 名对照者和 5 名患有心脏轻链淀粉样变性的患者进行了分析。在模型 II 中，粘度范围在 3.0（-19%）至 4.3 cP（+16%）之间，与标准值略有偏差。在非牛顿模型中，这种影响更为明显：粘度范围在 3.2 至 6.0 cP 之间，在低剪切率（即 <100 s）区域与标准值的偏差最大。这种影响反映在 EL 量化上：与模型 I 相比，模型 III 对血球比容高于 39.5%和低于 30%的患者产生了明显更高的 EL 值（高达+40%）或明显更低的值（低至-21%）。在特定患者的基础上考虑非牛顿血液行为可以提高 4D 流对心脏内能量评估的准确性，这可以作为一种非侵入性指标来区分健康和病理 LV。
