Effects of inflation pressures on mechanical environment of carotid after stent implantation by numerical simulation / 医用生物力学

Objective To investigate the effects of inflation pressures on mechanical environment of pathological carotid after stent implantation. Methods The carotid artery models with lipid and calcified plaques were constructed based on high-resolution MRI images. The artery-stent interaction model was developed in the finite element software. Based on the models, the von Mises stress distributions on the vascular wall and plague under 3 different inflation pressures (909, 1212 and 1515 kPa) were simulated. Results High inflation pressure would induce large Von Mises stress on the artery-stent interface. Moreover, the stress on the lipid plaque increased significantly with the increase of inflation pressure. However, the differences in stress distributions on the calcified plaque were very small under different inflation pressure. Conclusions Higher inflation pressure may severely damage the lipid plaque and artery-stent interface after stenting, which will contribute to the failure of stent. This research finding may provide clinical guidance for the selection of inflation pressure for arterial stent deployment and the assessment of plague stability after stent implantation．

Biomechanical research progress on abdominal aortic aneurysm enlargement after endovascular aneurysm repair / 医用生物力学

Clinically, abdominal aortic aneurysm (AAA) may continue to expand or even rupture after endovascular aneurysm repair (EVAR) due to endoleak or endotension. The existence of endoleak and endotension can significantly affect the mechanical/hemodynamic environment in AAAs, thus changing the strain and stresses on aneurysm wall, further influencing the transportation of low density lipoprotein (LDL), oxygen and nitric oxide (NO) in AAAs and aneurysm wall, which might eventually alter the biochemical environment and physiological property of aneurysm wall. This review focused on biomechanical mechanism of AAA enlargement after EVAR and its recent research progress, which indicated that reduction of the aneurysm wall strength due to deterioration of biomechanical environment (such as increase of tensile stress on aneurysm wall) and abnormity of biochemical environment (such as increase of LDL deposition, change of oxygen concentration) might be the source leading to AAA enlargement after EVAR. Based on previous studies, the authors propose that comprehensive investigations on AAA enlargement after EVAR from the perspective of biomechanics and mechanobiology have great research values and clinical significance, which will help clarify the mechanism of AAA enlargement after EVAR, as well as optimize the strategies of aneurysm repair surgery and designs of interventional medical devices.

Finite element analysis of neodymium: yttrium-aluminum-garnet incisions for the prevention of anterior capsule contraction syndrome / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Anterior capsular contraction syndrome is a potential complication of continuous curvilinear capsulorhexis (CCC). Three neodymium: yttrium-aluminum-garnet (Nd:YAG) laser relaxing incisions decrease anterior capsular contraction but the mechanism is unknown. The present study analyzed the biomechanical mechanism of three Nd:YAG laser relaxing incisions made to reduce anterior capsular contraction.</p><p><b>METHODS</b>A three-dimensional control model and a three-dimensional Nd:YAG model of the anterior capsule with an opening diameter of 6 mm were created. Three incisions of 1 mm in length were made centrifugally at intervals of 120° around the opening circle. The stress alterations of the anterior capsule after CCC with and without Nd:YAG relaxation were numerically simulated and compared.</p><p><b>RESULTS</b>In the control model, the stress was axially uniform in the inner area and relatively high near the inner rim of the opening. Meanwhile, in the Nd:YAG model, the stress level was very low in the inner opening areas, especially near the three incisions. The relaxing incisions in the Nd:YAG model significantly released the relatively high stress on the anterior capsule. Additionally, there was a high stress gradient near the relaxing incisions.</p><p><b>CONCLUSION</b>Biomechanical effects of stress release may be the preventive mechanism of Nd:YAG incision against anterior capsular contraction syndrome.</p>

Clinical application of the swirling flow mechanism in arterial prostheses and bypasses / 医用生物力学

Objective To apply the swirling flow mechanism to the design of arterial prostheses with small diameters and the arterial bypass surgery to resolve the acute thrombus in small diameter prostheses after implantation, and lessen the restenosis of bypassed arteries due to the formation of internal hyperplasia. Method The computational fluid dynamics (CFD) method was used to investigate the flow field and wall shear stress distribution of a new graft, an S type bypass and an axis deviated arterial bypass, which all had the swirling flow. In addition, the platelet adhesion under swirling flow and internal hyperplasia in S-type bypass were measured. Results The swirling flow can apparently enhance the wall shear stress (WSS) and suppress the platelet adhesion and internal hyperplasia. Conclusions The swirling flow can significantly improve the flow field in arterial graft and bypass to inhibit the acute thrombus in small diameter prostheses and internal hyperplasia after bypass surgery.