脑动脉狭窄致脑血流自调节功能受损的血流动力学机理

Cerebral auto-regulation is an important mechanism to maintain stable blood supply for the brain. Cerebrovascular stenoses weaken cerebral auto-regulation, which might be the principal inducement for stroke. Therefore, the study on the reason why cerebrovascular stenoses influences auto-regulation play a significant role in the precaution of stroke. We proposed the hypothesis that, cerebrovascular stenoses the change of critical factors for cerebral auto-regulation, such as the flow resistance and capacity of efferent blood vessels. In addition, the structure of Willis circle, and hypertension may also influence the cerebral auto-regulation. Accordingly, this study is to build a multi-scale coupling model with body circulation, cerebral arteries, and auto-regulation, to reveal the hemodynamic mechanism of the influence of cerebrovascular stenoses on auto-regulation; to conduct clinical trials, compare the experimental result of subjects with cerebrovascular stenoses and control subjects with the simulation, to clarify the critical factors influenced by cerebrovascular stenoses in auto-regulation; and to investigate the influence of Willis circle structure and hypertension on auto-regulation. The innovation of this study is to use mathematical model to clarify the hemodynamic mechanism of how cerebrovascular stenoses decrease cerebral auto-regulation, which may provide theoretic basis for the risk assessment of precaution of cerebrovascular stenoses and stroke.

脑血流自调节是人脑维持供血稳定的重要生理机制。脑动脉狭窄会导致脑血流自调节功能的减弱，这可能是脑卒中发生的重要诱因。因此，研究脑动脉狭窄影响自调节功能的机理，对于预防脑卒中具有重要的临床意义。我们提出如下假设：脑动脉狭窄可能导致下游血管对血流的阻力及顺应性等影响脑血流自调节功能的关键因素发生变化。另外，Willis环结构、高血压等也会影响自调节功能的运行。基于上述假设，本项目拟开展模型研究，构建体循环-脑动脉-自调节机制的多尺度耦合模型，揭示脑动脉狭窄对自调节功能影响的血流动力学机理；结合临床实验，对比正常人和脑动脉狭窄样本的实验结果和模型模拟结果，阐明自调节机制中受到脑动脉狭窄影响的关键因素；探明Willis环结构、高血压等对自调节功能的影响。本项目的创新之处在于通过模型研究，阐明脑动脉狭窄影响自调节机制的血流动力学机理，为脑动脉狭窄及脑卒中的风险评估和预警提供理论基础。

脑血流自调节机制是大脑自我保护，维持供血稳定的重要生理机制。但是现有研究表明，在脑动脉狭窄等疾病中，都观察到了脑血流自调节功能的减弱或损伤。研究脑动脉狭窄对脑血流自调节功能的影响，对于阐明脑卒中等脑血管事件的发生机理具有重要意义。本研究构建了体循环-脑动脉-自调节功能多维耦合的血流动力学模型，并在此基础上阐明了不同颈内动脉狭窄程度对脑血流自调节功能的影响；结果表明，当颈内动脉狭窄程度较低时，脑动脉血流量的平衡主要依靠Willis环的侧支循环来实现，而当狭窄程度较高是，脑动脉血流量的平衡主要依靠脑血流自调节机制来实现；颈内动脉的严重狭窄，对脑动脉血流及脑血流自调节影响明显，可能会改变部分脑动脉中的血流方向发生改变，并显著降低脑血流自调节能力。研究探明了Willis环结构及血压变化对脑血流自调节功能的影响；结果表明Willis环的完整性会显著影响脑血流自调节功能；体位及重力加速度引起的血压变化也会在短时间内影响脑血流自调节功能。上述工作共发表论文9篇，1篇已录用，申请发明专利4项，另有3项已授权，并成功实现转化。上述研究成果，可为脑血管病的机理认识、精确诊断和优化治疗提供一定参考。