Department of Surgery, University of California, San Francisco, CA, USA; Department of Bioengineering, University of California, San Francisco, CA, USA; San Francisco Veterans Affairs Medical Center, San Francisco, CA, USA.
School of Medicine, University of Texas Rio Grande Valley, Edinburg, TX, USA.
Comput Biol Med. 2021 Oct;137:104840. doi: 10.1016/j.compbiomed.2021.104840. Epub 2021 Sep 6.
Finite element (FE) mechanics models of the heart are becoming more sophisticated. However, there is lack of consensus about optimal element type and coupling of FE models to the circulation. We describe biventricular (left (LV) and right (RV) ventricles) FE mechanics model creation using hexahedral elements, airbags and a functional mockup interface (FMI) to lumped-parameter models of the circulation.
Cardiac MRI (CMR) was performed in two healthy volunteers and a single patient with ischemic heart disease (IHD). CMR images were segmented and surfaced, meshing with hexahedral elements was performed with a "thin butterfly with septum" topology. LV and RV inflow and outflow airbags were coupled to lumped-parameter circulation models with an FMI interface. Pulmonary constriction (PAC) and vena cava occlusion (VCO) were simulated and end-systolic pressure-volume relations (ESPVR) were calculated.
Mesh construction was prompt with representative contouring and mesh adjustment requiring 32 and 26 min Respectively. The numbers of elements ranged from 4104 to 5184 with a representative Jacobian of 1.0026 ± 0.4531. Agreement between CMR-based surfaces and mesh was excellent with root-mean-squared error of 0.589 ± 0.321 mm. The LV ESPVR slope was 3.37 ± 0.09 in volunteers but 2.74 in the IHD patient. The effect of PAC and VCO on LV ESPVR was consistent with ventricular interaction (p = 0.0286).
Successful co-simulation using a biventricular FE mechanics model with hexahedral elements, airbags and an FMI interface to lumped-parameter model of the circulation was demonstrated. Future studies will include comparison of element type and study of cardiovascular pathologies and device therapies.
心脏的有限元（FE）力学模型变得越来越复杂。然而，对于最佳元素类型以及 FE 模型与循环的耦合，仍然缺乏共识。我们描述了使用六面体元素、气囊和功能模拟接口（FMI）对循环的集中参数模型进行双心室（左心室（LV）和右心室（RV））FE 力学模型创建。
对两名健康志愿者和一名缺血性心脏病（IHD）患者进行心脏磁共振（CMR）检查。CMR 图像被分割和表面化，使用“带有隔瓣的薄蝴蝶”拓扑结构进行六面体元素网格划分。LV 和 RV 流入和流出气囊通过 FMI 接口与集中参数循环模型耦合。模拟肺缩窄（PAC）和腔静脉阻塞（VCO），并计算收缩末期压力-容积关系（ESPVR）。
网格构建非常迅速，代表性的轮廓和网格调整分别需要 32 分钟和 26 分钟。元素数量范围为 4104 到 5184 个，代表性的雅可比行列式为 1.0026±0.4531。基于 CMR 的表面与网格之间的一致性非常好，均方根误差为 0.589±0.321 毫米。志愿者的 LV ESPVR 斜率为 3.37±0.09，但 IHD 患者的斜率为 2.74。PAC 和 VCO 对 LV ESPVR 的影响与心室相互作用一致（p=0.0286）。
使用双心室 FE 力学模型与六面体元素、气囊和 FMI 接口对循环的集中参数模型进行成功的协同模拟得到了证明。未来的研究将包括对元素类型的比较以及心血管病理和器械治疗的研究。
