Yu Han, Del Nido Pedro J, Geva Tal, Yang Chun, Wu Zheyang, Rathod Rahul H, Huang Xueying, Billiar Kristen L, Tang Dalin
School of Biological Science and Medical Engineering, Southeast University, Nanjing, China.
Department of Cardiac Surgery, Boston Children's Hospital, Boston, MA, United States.
Front Physiol. 2020 Mar 19;11:198. doi: 10.3389/fphys.2020.00198. eCollection 2020.
Right ventricle (RV) failure is one of the most common symptoms among patients with repaired tetralogy of Fallot (TOF). The current surgery treatment approach including pulmonary valve replacement (PVR) showed mixed post-surgery outcomes. A novel PVR surgical strategy using active contracting bands is proposed to improve the post-PVR outcome. In lieu of testing the risky surgical procedures on real patients, computational simulations (virtual surgery) using biomechanical ventricle models based on patient-specific cardiac magnetic resonance (CMR) data were performed to test the feasibility of the PVR procedures with active contracting bands. Different band combination and insertion options were tested to identify optimal surgery designs.
Cardiac magnetic resonance data were obtained from one TOF patient (male, age 23) whose informed consent was obtained. A total of 21 finite element models were constructed and solved following our established procedures to investigate the outcomes of the band insertion surgery. The non-linear anisotropic Mooney-Rivlin model was used as the material model. Five different band insertion plans were simulated (three single band models with different band locations, one model with two bands, and one model with three bands). Three band contraction ratios (10, 15, and 20%) and passive bands (0% contraction ratio) were tested. RV ejection fraction was used as the measure for cardiac function.
The RV ejection fraction from the three-band model with 20% contraction increased to 41.58% from the baseline of 37.38%, a 4.20% absolute improvement. The RV ejection fractions from the other four band models with 20% contraction rate were 39.70, 39.45, and 40.70% (two-band) and 39.17%, respectively. The mean RV stress and strain values from all of the 21 models showed only modest differences (5-11%).
This pilot study demonstrated that the three-band model with 20% band contraction ratio led to 4.20% absolute improvement in the RV ejection fraction, which is considered as clinically significant. The passive elastic bands led to the reduction of the RV ejection fractions. The modeling results and surgical strategy need to be further developed and validated by a multi-patient study and animal experiments before clinical trial could become possible. Tissue regeneration techniques are needed to produce materials for the contracting bands.
右心室（RV）衰竭是法洛四联症（TOF）修复术后患者最常见的症状之一。目前的手术治疗方法包括肺动脉瓣置换术（PVR），术后结果不一。提出了一种使用主动收缩带的新型PVR手术策略，以改善PVR术后结果。为了测试带有主动收缩带的PVR手术的可行性，在不将有风险的手术程序应用于真实患者的情况下，使用基于患者特异性心脏磁共振（CMR）数据的生物力学心室模型进行了计算模拟（虚拟手术）。测试了不同的带组合和插入选项，以确定最佳手术设计。
从一名获得知情同意的TOF患者（男性，23岁）获取心脏磁共振数据。按照我们既定的程序构建并求解了总共21个有限元模型，以研究带插入手术的结果。使用非线性各向异性Mooney-Rivlin模型作为材料模型。模拟了五种不同的带插入计划（三个具有不同带位置的单带模型、一个双带模型和一个三带模型）。测试了三种带收缩率（10%、15%和20%）以及被动带（收缩率0%）。使用右心室射血分数作为心脏功能的衡量指标。
收缩率为20%的三带模型的右心室射血分数从基线的37.38%增加到41.58%，绝对改善了4.20%。收缩率为20%的其他四个带模型的右心室射血分数分别为39.70%、39.45%和40.70%（双带）以及39.17%。所有21个模型的右心室平均应力和应变值仅显示出适度差异（5%-11%）。
这项初步研究表明，收缩率为20%的三带模型使右心室射血分数绝对提高了4.20%，这被认为具有临床意义。被动弹性带导致右心室射血分数降低。在进行临床试验之前，建模结果和手术策略需要通过多患者研究和动物实验进一步开发和验证。需要组织再生技术来生产用于收缩带的材料。
