Hemodynamic Study For The Elongation And Tortuosity Of Internal Carotid Artery And Vertebral Artery

Objective: to establish a theoretical model for the elongation and tortuosity of internal carotid artery and vertebral artery, to analyze and calculate the variance in hemodynamic parameters of the tortuous elongated internal carotid artery and vertebral artery. To summarize the hemodynamic rule of blood flow in a tortuous elongated artery and to explore the relationship of cerebral ischemia and tortuous elongated internal carotid artery and vertebral artery.Methods: Numerical simulation and hydrodynamic experiment simulation A hemodynamic mathematical model was established at first, then taking the internal carotid artery as a prototype, a geometric model of a tortuous elongated artery was constructed according to the normal physiological and anatomical parameters of internal carotid artery. The boundary conditions and calculation conditions of blood flow are proposed. The numerical simulation of the blood flow in the tortuous elongated artery is carried out with finite element method. A set of simulation experimental equipment was constructed according to the same physiological and anatomical parameters of internal carotid artery. The tortuous elongated artery was simulated with silica gel tube. Pressure drop was measured at different angle of the elongated artery while flow rate was fixed. The results of numerical simulation and experiment simulation were analyzed and validated.Clinical data measurement Hemodynamic parameters of internal carotid artery and vertebral artery were measured in 15 cases of normal control group and in 15 cases with the elongation and tortuosity of internal carotid artery and vertebral artery. The datas of SPV, EDV and Vm were measured and recorded by Doppler ultrasound at internal carotid artery , vertebral artery, pre-tortuous and post-tortuous artery. the datas of flow rate were calculated. Blood pressure was measured by microcatheter connecting a pressure transducer at internal carotid artery, vertebral artery, pre-tortuous and post-tortuous artery. The diameter and length of the above artery were measured and calculated by the computer of DSA machine.Data analysis Datas of numerical simulation and experimental simulation were compared with clinical datas. The variance of hemodynamic parameters such as elongated length, pressure drop, flow velocity and flow rate was analyzed. The fundamental regularity of variations in hemodynamic parameters caused by the tortuous elongated artery was interpreted.Case review 714 cases with complete cervical angiograms were reviewed. The clinical findings of patients with elongation and tortuosity of internal carotid artery and vertebral artery were analyzed. A case-control study was done in the group of 72 cases with kinking of internal carotid artery and vertebral artery (GradeⅢ) and control group of 72 cases without elongation of internal carotid artery and vertebral artery, and also without moderate and severe stenosis of intracranial or extracranial artery. The incidence of cerebral ischemia in the group with kinking of internal carotid artery and vertebral artery was compared with the control group.Results: Numerical simulation results indicated the hydrodynamic parameters such as pressure drop and flow field changed at different angle of tortuous artery. The flow velocity changed remarkably at the curved part of tortuous artery. Pressure drop of blood flow and elongated length of artery is increased with diminution of the angle of tortuous artery. The pressure drop of blood flow changes significantly when the angle of tortuous artery is between 20°and 30°. The pressure drop of blood flow is the largest when the angle of tortuous artery is approximately 30°. Experimental simulation results showed the same trends in the angle and pressure drop curve as numerical simulation. Experimental simulation results are coincident with numerical simulation results properly. Clinical measurement datas disclosed the same trend in the same curve as numerical simulation and experimental simulation. Pressure drop of blood pressure increased, pre-tortuosity flow velocity speeded, post-tortuosity flow rate decreased obviously when the angle of tortuous elongated artery was less than 30°.The prevalence of elongation and tortuosity of cervical artery was 25.1%(179/174) in 714 cases reviewed. Of the total, prevalence of common carotid artery was 1.5%(11/714), internal carotid artery was 8.3%(59/714), vertebral artery was 15.3%(109/714). The prevalence of elongation and tortuosity of cervical artery was 30.6%(158/516) in patients with ischemia cerebrovascular disease. Among it, internal carotid artery was 10.1%(52/516) and vertebral artery was 15.3%(98/516). Patients older than 60 was 74.4%(125/168) in all patients with elongation and tortuosity of internal carotid artery and vertebral artery. The incidence rate of cerebral ischemia in the group with kinking of internal carotid artery and vertebral artery was higher than the control group (p＜0.05).Conclusions: A mathematical theoretical model and a set of experimental simulation equipment for the elongation and tortuosity of internal carotid artery and vertebral artery was established. They are usability validated by compared with clinical measurement results. The elongation and tortuosity of internal carotid artery and vertebral artery results in elongation of the length of artery, elongated length is related to the angle of tortuous elongated artery, elongation length become longer with the diminutus of angle of tortuous elongated artery. The elongation and tortuosity of internal carotid artery and vertebral artery results in decrease of blood pressure and flow rate, decrease of blood pressure and flow rate is obviously when the angle of tortuous elongated artery is less than 30°. Kinking of internal carotid artery and vertebral artery may be one of factors related to attack of cerebral ischemia on certain conditions.