Toeg Hadi Daood, Abessi Ovais, Al-Atassi Talal, de Kerchove Laurent, El-Khoury Gebrine, Labrosse Michel, Boodhwani Munir
Division of Cardiac Surgery, University of Ottawa Heart Institute, Ottawa, Ontario, Canada.
Department of Mechanical Engineering, University of Ottawa, Ottawa, Ontario, Canada.
J Thorac Cardiovasc Surg. 2014 Oct;148(4):1739-1745.e1. doi: 10.1016/j.jtcvs.2014.05.004. Epub 2014 May 6.
Aortic valve (AV) repair (AVr) has become an attractive alternative to AV replacement for the correction of aortic insufficiency; however, little clinical evidence exists in determining which biomaterial at AVr would be optimal. Cusp replacement in AVr has been associated with increased long-term AVr failure. We measured the hemodynamic and biomaterial properties using an ex vivo porcine AVr model with clinically relevant biomaterials and generated a finite element model to ascertain which materials would be best suited for valve repair.
Porcine aortic roots with intact AVs were placed in a left heart simulator mounted with a high-speed camera for baseline valve assessment. The noncoronary cusp was excised and replaced with autologous porcine pericardium, glutaraldehyde-fixed bovine pericardial patch (Synovis), extracelluar matrix scaffold (CorMatrix), or collagen-impregnated Dacron (Hemashield). The hemodynamic parameters were measured for a range of cardiac outputs (2.5-6.5 L/min) after repair. The biomaterial properties and St Jude Medical pericardial patch were determined using pressurization experiments. Finite element models of the AV and root complex were constructed to determine the hemodynamic characteristics and leaflet stresses.
The geometric orifice areas after repair were significantly reduced in the Hemashield (P<.05) and CorMatrix (P=.0001) groups. Left ventricular work increased with increasing cardiac output (P=.001) in unrepaired valves, as expected, and was similar among all biomaterial groups. Finite element modeling of the biomaterials displayed differences in the percentage of changes in total Von Mises stress for both replaced (noncoronary cusp) and nonreplaced left and right cusps with the St Jude Medical pericardial patch (+4%, +24%) and autologous porcine pericardium (+5, +26%), with a lower percentage of changes than for the bovine pericardial patch (+12%, +27%), Hemashield (+30%, +9%), and CorMatrix (+13%, +32%).
The present study has shown that postrepair left ventricular work did not increase despite a decrease in geometric orifice areas in the Hemashield and CorMatrix groups. The autologous porcine pericardium and St Jude Medical pericardial patch had the closest profile to normal AVs; therefore, either biomaterial might be best suited. Finally, the increased stresses found in the bovine pericardial patch, Hemashield, and CorMatrix groups might, after prolonged tensile exposure, be associated with late repair failure.
主动脉瓣修复术（AVr）已成为治疗主动脉瓣关闭不全的一种有吸引力的替代主动脉瓣置换术的方法；然而，在确定AVr中使用哪种生物材料最为理想方面，临床证据很少。AVr中的瓣叶置换与长期AVr失败率增加有关。我们使用具有临床相关生物材料的离体猪AVr模型测量了血流动力学和生物材料特性，并生成了有限元模型，以确定哪种材料最适合瓣膜修复。
将具有完整主动脉瓣的猪主动脉根部置于装有高速摄像机的左心模拟器中，进行基线瓣膜评估。切除无冠状动脉瓣叶，并用自体猪心包、戊二醛固定的牛心包补片（Synovis）、细胞外基质支架（CorMatrix）或胶原浸渍涤纶（Hemashield）进行置换。修复后，在一系列心输出量（2.5 - 6.5升/分钟）范围内测量血流动力学参数。通过加压实验确定生物材料特性和圣犹达医疗心包补片的特性。构建主动脉瓣和根部复合体的有限元模型，以确定血流动力学特征和瓣叶应力。
Hemashield组（P<0.05）和CorMatrix组（P = 0.0001）修复后的几何开口面积显著减小。如预期的那样，未修复瓣膜的左心室做功随心输出量增加而增加（P = 0.001），并且在所有生物材料组中相似。生物材料的有限元建模显示，与圣犹达医疗心包补片（分别增加4%、24%）和自体猪心包（分别增加5%、26%）相比，置换（无冠状动脉瓣叶）和未置换的左、右瓣叶的总冯·米塞斯应力变化百分比存在差异，其变化百分比低于牛心包补片（分别增加12%、27%）、Hemashield（分别增加30%、9%）和CorMatrix（分别增加13%、32%）。
本研究表明，尽管Hemashield组和CorMatrix组的几何开口面积减小，但修复后左心室做功并未增加。自体猪心包和圣犹达医疗心包补片的特性与正常主动脉瓣最接近；因此，这两种生物材料可能最为合适。最后，在牛心包补片、Hemashield和CorMatrix组中发现的应力增加，在长期拉伸暴露后，可能与晚期修复失败有关。
