Ge Liang, Haraldsson Henrik, Hope Michael D, Saloner David, Guccione Julius M, Ratcliffe Mark B, Tseng Elaine E
Department of Surgery, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA, USA.
Department of Radiology, University of California San Francisco and San Francisco VA Medical Centers, San Francisco, CA, USA.
J Heart Valve Dis. 2016 Jul;25(4):424-429.
Transcatheter aortic valve replacement (TAVR) has revolutionized the treatment of severe aortic stenosis in intermediate, high-risk, and inoperable patients. TAVR has multiple access routes, including transfemoral (TF), transapical (TA), direct aortic (DA), axillary, transcarotid, and transcaval. The most commonly applied algorithm is a TF-first approach, where only when patients are unsuitable for TF are alternatives such as TA considered. An infrequent - but dreaded - risk is left ventricular (LV) apical bleeding from tearing or rupture with the TA approach. With burgeoning transcatheter mitral technology that requires a TA approach, the study aim was to develop a mathematical model to determine suture forces for TA closure.
Preoperative cine-cardiac magnetic resonance imaging (MRI) was used to acquire three-dimensional (3D) LV geometry at end-systole and end-diastole. Endocardial and epicardial boundaries were manually contoured using MeVisLab, a surface reconstruction software. 3D surfaces of endocardium and epicardium were reconstructed, and surfaces at end-systole were used to create a 3D LV finite element (FE) mesh. TA access was mimicked by developing a 10-mm defect within the LV FE model. The LV apex was closed using a virtual suture technique in FE analysis with the application of two virtual sutures. After virtual closure, a FE analysis was performed of LV model diastolic filling and systolic contraction.
Proof of concept was achieved to develop an LV transapical access site and perform FE analysis to achieve closure. The FE method of virtual suture technique successfully approximated the LV apical defect. The peak axial forces on virtual sutures at end-diastole and end-systole were 0.445N and 0.736N, respectively.
A LV TA access model was mathematically developed that could be used to evaluate the suture tension of the TA closure process. Further development of this approach may be useful to risk-stratify patients in the future for LV apical tearing. Video 1: Cine cardiac magnetic resonance imaging of the left ventricle. Video 2: Slow motion animation of left ventricular baseline simulation. Video 3: Animation of the virtual suturing process.
经导管主动脉瓣置换术（TAVR）彻底改变了中、高风险及无法手术的严重主动脉瓣狭窄患者的治疗方式。TAVR有多种入路途径，包括经股动脉（TF）、经心尖（TA）、直接主动脉（DA）、腋动脉、经颈动脉和经腔静脉。最常用的算法是先尝试经股动脉入路，只有当患者不适合经股动脉入路时才考虑如经心尖入路等其他替代方法。一种罕见但可怕的风险是经心尖入路时左心室（LV）心尖因撕裂或破裂而出血。随着需要经心尖入路的经导管二尖瓣技术的迅速发展，本研究的目的是建立一个数学模型来确定经心尖闭合的缝合力。
术前心脏电影磁共振成像（MRI）用于获取收缩末期和舒张末期的三维（3D）左心室几何形状。使用表面重建软件MeVisLab手动勾勒心内膜和心外膜边界。重建心内膜和心外膜的3D表面，并使用收缩末期的表面创建3D左心室有限元（FE）网格。通过在左心室有限元模型内创建一个10毫米的缺损来模拟经心尖入路。在有限元分析中使用虚拟缝合技术，应用两根虚拟缝线关闭左心室心尖。虚拟闭合后，对左心室模型的舒张期充盈和收缩期收缩进行有限元分析。
成功实现了开发左心室经心尖入路部位并进行有限元分析以实现闭合的概念验证。虚拟缝合技术的有限元方法成功地模拟了左心室心尖缺损。舒张末期和收缩末期虚拟缝线上的峰值轴向力分别为0.445N和0.736N。
通过数学方法建立了左心室经心尖入路模型，可用于评估经心尖闭合过程中的缝合张力。该方法的进一步发展可能有助于未来对左心室心尖撕裂患者进行风险分层。视频1：左心室心脏电影磁共振成像。视频2：左心室基线模拟慢动作动画。视频3：虚拟缝合过程动画。
