Biomechanical Parameters for Carotid Risk Assessment: A Review / 医用生物力学

Carotid is in a high risk of atherosclerosis due to its special geometric features and complex flow characteristics. Various biomechanical parameters are practical tools for carotid risk assessment. It has beenwidely accepted that oscillatory low shear environment promotes plaque formation. Based on this, more and more biomechanical indexes have been proposed, such as time-average wall shear stress, oscillatory shear index, relative residence time and so on. In this paper, multiple biomechanical parameters were introduced from the perspectives of shear stress and its temporal and spatial variation, turbulence, platelet transport and activation, stress concentration in vascular wall, etc. The development trend of biomechanical parameters related to carotid artery risk assessment was also analyzed, so as to provide the theoretical basis for more comprehensive and rapid carotid risk assessment

Primary study on recognition of vascular stiffness based on wavelet scattering neural network / 生物医学工程学杂志

Cardiovascular disease is the leading cause of death worldwide, accounting for 48.0% of all deaths in Europe and 34.3% in the United States. Studies have shown that arterial stiffness takes precedence over vascular structural changes and is therefore considered to be an independent predictor of many cardiovascular diseases. At the same time, the characteristics of Korotkoff signal is related to vascular compliance. The purpose of this study is to explore the feasibility of detecting vascular stiffness based on the characteristics of Korotkoff signal. First, the Korotkoff signals of normal and stiff vessels were collected and preprocessed. Then the scattering features of Korotkoff signal were extracted by wavelet scattering network. Next, the long short-term memory (LSTM) network was established as a classification model to classify the normal and stiff vessels according to the scattering features. Finally, the performance of the classification model was evaluated by some parameters, such as accuracy, sensitivity, and specificity. In this study, 97 cases of Korotkoff signal were collected, including 47 cases from normal vessels and 50 cases from stiff vessels, which were divided into training set and test set according to the ratio of 8 : 2. The accuracy, sensitivity and specificity of the final classification model was 86.4%, 92.3% and 77.8%, respectively. At present, non-invasive screening method for vascular stiffness is very limited. The results of this study show that the characteristics of Korotkoff signal are affected by vascular compliance, and it is feasible to use the characteristics of Korotkoff signal to detect vascular stiffness. This study might be providing a new idea for non-invasive detection of vascular stiffness.

Design and mechanical properties of biodegradable polymeric stent / 生物医学工程学杂志

Biodegradable stents (BDSs) are the milestone in percutaneous coronary intervention(PCI). Biodegradable polymeric stents have received widespread attention due to their good biocompatibility, moderate degradation rate and degradation products without toxicity or side effects. However, due to the defects in mechanical properties of polymer materials, the clinical application of polymeric BDS has been affected. In this paper, the BDS geometric configuration design was analyzed to improve the radial strength, flexibility and reduce the shrinkage rate of biodegradable polymeric stents. And from the aspects of numerical simulation, in vitro experiment and animal experiment, the configuration design and mechanical properties of biodegradable polymeric stents were introduced in detail in order to provide further references for the development of biodegradable polymeric stents.

Effects of Straightening Phenomenon Caused by Stent Implantation on Local Biomechanical Environment of the Vascular Wall / 医用生物力学

Objective To investigate the influence of straightening phenomenon caused by stent implantation on biomechanical environment changes in vascular lesions, so as to explore biomechanical mechanism of restenosis and stent optimization. Methods Based on the computed tomography (CT) images of a patient, the balloon model, the left anterior descending coronary(LAD) artery model and two stent models (idealized stent and straightened stent) were reconstructed by Mimics, Geomagic and Pro/E software. The balloon-stent-LAD artery mechanical models were then established with the ABAQUS software. Based on the numerical simulation results, the influence of straightening phenomenon on mechanical environment at vascular lesions was analyzed. Results When the stents were expanded under the same inflation pressures (1.013 MPa), the Von Mises stress increased on vascular wall of the straightened stent model compared with the idealized stent model, and stress concentration occurred especially at the proximal and distal area of the stented regions and on the myocardial surface. The average and the maximum Von Mises stress on vascular wall of the idealized stent model were 0.39 MPa and 5.12 MPa, respectively. The average and the maximum Von Mises stress on vascular wall of the straightened stent model were 0.45 MPa and 7.43 MPa, respectively. Conclusions The straightening phenomenon caused by stent implantation would change the distribution of Von Mises stress and induce stress concentration. This kind of mechanical environment would cause greater damage to vascular wall, then might cause mechanical injury and vascular remodeling, leading to a higher risk of neointimal hyperplasia and subsequent restenosis. The research findings will be helpful for explaining the mechanism of in-stent restenosis, and may provide clinical guidance for the interventional surgery and optimization of stent design.

Biomechanical research progress on sex differences of abdominal aortic aneurysm / 生物医学工程学杂志

The phenomenon of sex differences exists in patients who have abdominal aortic aneurysms (AAA). The occurrence rate of AAA is higher in male, while the rates of rupture and postoperative mortality are higher for female. This phenomenon of sex differences would affect the diagnosis, treatment and postoperative rehabilitation for AAA patients. This article reviewed the recent research status of sex differences on AAA, and explored the phenomenon of sex differences from the aspects of threshold determination, biomechanics and mechanobiology. This review points out that the sex differences on AAA could ascribe to the differences of biomechanical environment and biological properties induced by the vascular size, anatomy structure and structure components of abdominal aortic artery. The comprehensive investigations of the sex differences on AAA could help to optimize the diagnosis, treatment and device design, patient care and rehabilitation strategy of AAA based on sex differences phenomenon.