The Hemodynamic Study on the Effects of Entry Tear and Coverage in Aortic Dissection

Nowadays,cardiovascular disease has gradually become the number one killer of human health.The Stanford type-A aortic dissection is a relatively common cardiovascular disease with potential hazards.The disease is caused by a partialtearing of the aortic intima.Thoracic endovascular aortic repair(TEVAR)is one of the most effective treatment for type A aortic dissection and has been widely used clinically to achieve thrombosis and reduce pressure by covering the incision tear in the FL.However,the effect of entry tear location on type-A aortic dissection and the prognosis of TEVAR intervention are unclear.In this work,the hemodynamic effects of the type-A aortic dissection in different entry and covering entry tear position were mainly studied.It can provide a new method or idea in the field of the aortic dissection hemodynamics,which is of great significance to provide a basic theoretical research on the development of aortic dissection in the aspect of clinical judgment.Two type-A aortic dissection models with different entry tear positions(Model 1:the entry tear was located at the entrance of the ascending aorta,Model 2:the entry tear was located at the starting position of the descending aorta)were reconstructed according to the computed tomography(CT)images of the patients.In our study,the thoracic aortic endovascular repair was simulated by covering the entry tear(Model 3).Then,the semi-automatic adaptive technology HyperMeshl0.0(Altair HyperWorks,Troy,Ml,USA)mesh generator was used to generate the high-quality tetrahedral 3D mesh.To clarify the hemodynamic effects of entry tear and coverage in aortic blood flow pattern,the comparative study on the true lumen(TL)and false lumen(FL)blood flow patterns of three models were carried out numerically(the time-dependent pulsatile waveform of pressure boundary conditions used at the aortic inlet were consistent with Rapezzis’s work,time-dependent pulsatile waveform of velocity at the descending aorta outlet and the time-dependent pulsatile waveform of pressure at the brachiocephalic artery,left common carotid artery,and left subclavian artery were obtained from the work of Olufsenet et al).The velocity vector,flow ratio,pressure,time-average wall shear stress(TAWSS)and relative residence time(RRT)were calculated to evaluate the hemodynamic changes.The results of this work indicated that(Ⅰ)the velocity was higher at the entry tear in aorta entrance;(Ⅱ)the helical development of the TL and FL might be related to the helical nature of aortic arch;(Ⅲ)the blood flow which passing the FL of Model 1,Model 2 and Model 3 in one cardiac cycle were approximately 26.63%,13.39%and 1%,respectively;(Ⅳ)the difference in intima wall pressure among the TL and FL was found varied a lot and shown a strong pulsation;(Ⅴ)the TAWSS distribution in TL and FL were quite different(the TAWSS in TL intima>8 Pa,the TAWSS in FL intima<4 Pa).In brief,the aortic morphology and location of the entry tear were found to have a significant effect on the hemodynamic of the aortic dissection.What’s more,we found that the risk of the aortic rupture could be higher if the position of entry tear is closer to the ascending aorta.By covering the entry tear to simulate TEVAR,the pressure of FL was reduced,which could provide some help for the treatment of early retrograde type-A dissection.