颈动脉易损斑块破裂风险血流动力学机理的数值模拟及实验研究

Stroke is the leading cause of mortality and long-term morbidity in China. About 80% of all strokes are ischemic and approximately 25- 50% of these are caused by unstable carotid artery plaque. It is thrombosis, superimposed on a rutptured or eroded carotid plaque, that precipitates the life-threatening ischemic stroke. Carotid plaque vulnerability assessment and the ability to predict possible future plaque rupture are of vital importance for early diagnosis, prevention and treatment of ischemic stroke. A major problem to overcome is the lack of good evidence with which to target patients above specific risk thresholds and to identify those who may benefit from therapeutic intervention. Current selection criteria for carotid endarterectomy and stenting are predominantly determined by the grade of stenosis and symptomatology, but there is growing awareness that stenosis severity alone has limited value in predicting plaque stability and critical plaque components and biological processes, including inflammation, neovascularization and local critical stress conditions are key factors in the plaque rupture process and should be considered in an integrated way for better plaque vulnerability assessment and rupture risk predictions. A major challenge for plaque assessment is the lack of realistic biomechanical lesion information based on in vivo patient data that both ruptured and non-ruptured plaques could be compared and analyszed. On the basis of our previous in vivo and in vitro study, we try to use in vivo patient data to construct MRI- and histology- based computational fluid dynamics(CFD) and finite element analysis models with accurate stress and flow information, aim to investigate the qualitative and quantitative correlations between critical mechanical conditions at critical sites in the plaque and specific plaque's morphological and compositional features known to be linked to plaque vulnerability, and to establish an in vivo benchmark for more accurate stress-based plaque vulnerability assessment schemes.

颈动脉粥样硬化斑块的破裂和继发血栓形成是导致缺血性脑中风的最主要原因。颈动脉斑块局部的血流动力学状况及斑块的形态、成分和生物学活性均与颈动脉斑块的破裂风险密切相关。由于缺少在体检测血流动力学参数及显示斑块成分和生物学活性的有效方法，无法准确定性、定量评价颈动脉斑块破裂的风险，目前临床上在颈动脉斑块的治疗适应证选择方面仍缺乏可靠的理论依据。本课题以前期实验研究为基础，拟应用在体无创性测量的真实解剖和血流数据进行狭窄颈动脉的有限元模型构建和血流动力学数值模拟，探讨颈动脉斑块危险表型的血流动力学机理，摸索定性及定量评价颈动脉易损斑块破裂风险的影像学及生物力学指标。

颈动脉粥样硬化斑块的破裂和继发血栓形成是导致缺血性脑中风的最主要原因。颈动脉斑块局部的血流动力学状况及斑块的形态、成分和生物学活性均与颈动脉斑块的破裂风险密切相关。由于缺少在体检测血流动力学参数及显示斑块成分和生物学活性的有效方法，因此无法准确地定性、定量评价颈动脉斑块破裂的风险。目前临床上在颈动脉斑块的治疗适应证选择方面仍缺乏可靠的理论依据。因为血流动力学在颈动脉易损斑块的破裂中有着重要的影响，但是从血流动力学的角度研究易损斑块的研究却很少，因此本课题以前期实验研究为基础，采用在体无创性测量的真实解剖和血流数据和血管造影CT图像，构建了7例颈动脉溃疡斑块的三维个性化模型，经过合适的网格划分，进行狭窄颈动脉的血流动力学数值模拟,探讨颈动脉溃疡斑块破裂的血流动力学机理，摸索定性及定量评价颈动脉溃疡斑块破裂风险的影像学及生物力学指标。结果表明，溃疡周围血流的异常可能导致斑块破裂的进一步发展，血栓形成后由于血流的作用会在狭窄下游形成栓塞进而引发中风。单一溃疡中溃疡下游，两个连续溃疡中的两个溃疡之间的位置的高壁面切应力容易使溃疡斑块进一步发生严重的破裂。此外，由于溃疡上游和下游受到同向不同大小的壁面切应力，溃疡处可能会因此产生的拉扯而发生严重破裂。溃疡区域的高壁面切应力梯度也会造成溃疡斑块的进一步破裂。总体来看，本项目从血流动力学的角度对斑块的破裂机理进行了阐释，研究工作取得了较好的成果。