ABSTRACT
Objective Based on hemodynamic analysis, to investigate the cause of distal re-entry tear in Stanford type B aortic dissection after thoracic endovascular aortic repair (TEVAR).Methods A patient with type B aortic dissection was reexamined regularly with computed tomography angiography (CTA) at 1st month, 6th month, 12th month and 24th month after TEVAR. Based on the CTA images in each period, three-dimensional (3D) aorta models were reconstructed to perform morphological analysis and hemodynamic simulation.Results Compared with the diameter at 1st month after TEVAR, the diameter of true lumen at 12 months after TEVAR increased by 1.8 times and the global distortion of aorta increased by 16.67%. At postoperative 1st, 6th and 12th month, the maximum blood velocities at the new entry tear in systole were 69.6%, 33.7% and 92.1% higher than the average ones at distal landing zone, and the maximum wall shear stresses (WSSs) were 2.52, 2.32 and 3.52 times of the average WSSs respectively. In addition, the maximum time-averaged WSS (TAWSS) at 1st, 6th and 12th month after TEVAR were 1.88, 2.53 and 3.62 times of the mean TAWSS respectively.ConclusionsThe morphology of the aorta remodeled after TEVAR, and a sudden change in the diameter of true lumen occurred at distal anchoring zone and continued to increase. As a result, the blood flow velocity in this area accelerated, and the intima was continuously exposed to high WSS, leading to the redissection.
ABSTRACT
Objective To study effects from sand therapy of Uyghur medicine on hemodynamics in femoral artery branch and stress, so as to further discuss the functions and mechanisms of Uyghur sand therapy for treatment of femoral artery thrombosis formation. Methods Uyghur sand therapy was conducted on the subjects by indoor Uyghur sand therapy system. The peak values of blood flow velocity, inner diameter and resistance index (RI) of femoral artery before and after receiving Uyghur sand therapy were measured by the ultra-portable Doppler Diagnostic Ultrasound System for statistic analysis. Three-dimensional fluid-solid coupling model of femoral artery branch was reconstructed, and blood flow velocity, pressure, wall shear stress in the flow field as well as the equivalent stress, strain, total displacement on femoral artery wall were simulated and analyzed by the ANSYS Workbench. Results After receiving Uyghur sand therapy, the mean peak values of blood flow velocity and inner diameter of femoral artery increased by 32.43% and 2.68%, while the mean values of RI decreased by 4.88%, which showed it had the statistical difference(P0.05).Besides, the maximum values of blood flow velocity, pressure and wall shear stress increased by 29.91%，68.51%,46.54%,respectively, while the maximum values of equivalent stress, equivalent strain, total displacement on femoral artery wall increased by 65.85%，45.45%，44%, respectively, after receiving Uyghur sand therapy. Conclusions Uyghur sand therapy can increase blood flow velocity and decrease RI obviously，and help to expand the inner diameter of femoral artery to make blood circulation inside improved. With Uyghur sand therapy, the shear stress, blood flow velocity, pressure as well as the stress, strain, total displacement on femoral artery walls also increase, meanwhile，high pressure area on femoral artery branch reduces to some extent, which shows it plays a certain positive role in reducing atherosclerosis and thrombus formation inside femoral artery.
ABSTRACT
The present study in angulated coronary stenosis used human in vivo hemodynamic parameters and computed simulation, both qualitatively and qualitatively, to evaluate the influence of flow velocity and wall shear stress (WSS) on coronary atherosclerosis, the changes of hemodynamic indices following coronary stenting, and their effect on evolving in-stent restenosis. Initial and follow-up coronary angiographies in patients with angulated coronary stenosis were performed (n=60). The optimal degree of coronary stenting for angulated coronary stenosis had two models, the less than 50% angle changed group (model 1, n=33) and the more than 50% angle changed group (model 2, n=27). This angle change was based on the percentage change of vascular angle between pre- and post-intracoronary stenting. The flow-velocity wave obtained from in vivo intracoronary Doppler study data was used for in vitro numerical simulation. Spatial and temporal patterns of the flow-velocity vector and recirculation area were drawn throughout the selected segment of coronary models. WSS of pre- and post-intracoronary stenting was calculated from three-dimensional computer simulation. As results, follow-up coronary angiogram demonstrated significant difference in the percentage of diameter stenosis between the two groups (group 1: 40.3 +/- 30.2 vs. group 2: 25.5 +/- 22.5%, p < 0.05). Negative shear area on 3D simulation, which is consistent with the re-circulation area of flow vector, was noted on the inner wall of the post-stenotic area before stenting. The negative WSS disappeared after stenting. High spatial and temporal WSS before stenting fell within the range of physiologic WSS after stenting. This finding was more prominent in model 2 (p < 0.01). The present study suggests that hemodynamic forces exerted by pulsatile coronary circulation, termed WSS, might affect the evolution of atherosclerosis within the angulated vascular curvature. Moreover, geometric characteristics, such as the angular difference between pre- and post- intracoronary stenting might define optimal rheologic properties for vascular repair after stenting.