基于计算流体力学的主动脉瓣二叶畸形合并巨大升主动脉瘤患者血流动力学研究

Analysis of hemodynamics in patients with bicuspid aortic valve complicated with giant ascending aortic aneurysm based on computational fluid dynamics

目的通过计算流体力学数值模拟对主动脉瓣二叶畸形合并巨大升主动脉瘤患者进行分析,并描述其血流动力学特点,预测可能的生物力学机制。方法基于2017年8月5日就诊于首都医科大学附属北京安贞医院的1例38岁男性无症状的主动脉瓣二叶畸形合并直径为10.5 cm升主动脉瘤患者的磁共振成像及流体数据,建立计算流体力学模型并分析其流速、压力及壁面切应力。结果通过与瞬时速度矢量的切线绘制巨大动脉瘤模型一个心动周期的3个时间点的流线,相比正常的主动脉入口速度(1.0~1.7 m/s),入口流速变快,最高可达2.4 m/s。高速的中心血流进入巨大的瘤腔后速度迅速下降,瘤腔外围的血流速度始终很慢;升主动脉压力较正常三叶瓣增加;瘤腔内的壁面切应力降低,其分布较为均匀,未出现突然增高或降低区域。结论患者均匀分布的壁面切应力可能是巨大动脉瘤破裂的保护因素。计算流体力学有助于解释二叶式瓣主动脉瓣可能在升主动脉中引起巨大动脉瘤的生物力学机制,并为我们提供巨大动脉瘤治疗的策略信息。

Objective To analyze the patients with bicuspid aortic valve complicated with giant ascending aortic aneurysm by computational fluid dynamics numerical simulation,to describe the hemodynamic characteristics,and to predict possible biomechanical mechanisms.Methods Based on magnetic resonance imaging and fluid data of a 38 years old male patient with bicuspid aortic valve complicated with ascending aortic aneurysm 10.5 cm in diameter admitted to Beijing Anzhen Hospital,Capital Medical University at August 5,2017,computational fluid dynamics model was established and the flow rate,pressure and wall shear stress were analyzed.Results The streamlines of three time points in a cardiac cycle of giant aneurysm model were drawn by tangent to instantaneous velocity vector,and compared with the normal aortic inlet velocity(1.0-1.7 m/s),the inlet velocity became faster,up to 2.4 m/s.After the high-speed central blood flow entering the huge tumor cavity,the speed dropped rapidly.Blood flow velocity at the periphery of the tumor cavity was always slow.The ascending aortic pressure was higher than normal.The wall shear stress in the cavity decreased.The distribution was uniform,and no areas of sudden increase or decrease were observed.Conclusions Uniformly distributed wall shear stress in patients may be a protective factor in the rupture of giant aneurysms.The computational fluid dynamics is conducive to explain the biomechanics mechanism that bicuspid aortic valve may cause giant ascending aortic aneurysm and provide us with the strategy information for treatment strategies in giant aneurysm patients.