ABSTRACT
The prevalence of cardiovascular disease in our country is increasing, and it has been a big problem affecting the social and economic development. It has been demonstrated that early intervention of cardiovascular risk factors can effectively reduce cardiovascular disease-caused mortality. Therefore, extensive implementation of cardiovascular testing and risk factor screening in the general population is the key to the prevention and treatment of cardiovascular disease. However, the categories of devices available for quick cardiovascular testing are limited, and in particular, many existing devices suffer from various technical problems, such as complex operation, unclear working principle, or large inter-individual variability in measurement accuracy, which lead to an overall low popularity and reliability of cardiovascular testing. In this study, we introduce the non-invasive measurement mechanisms and relevant technical progresses for several typical cardiovascular indices (e.g., peripheral/central arterial blood pressure, and arterial stiffness), with emphasis on describing the applications of biomechanical modeling and simulation in mechanism verification, analysis of influential factors, and technical improvement/innovation.
Subject(s)
Humans , Arterial Pressure , Biomechanical Phenomena , Blood Pressure , Blood Pressure Determination , Reproducibility of Results , Risk FactorsABSTRACT
External support stent is a potential means for restricting the deformation and reducing wall stress of the vein graft, thereby improving the long-term patency of the graft in coronary artery bypass surgery. However, there still lacks a theoretical reference for choosing the size of stent based on the diameter of graft. Taking the VEST (venous external support) stent currently used in the clinical practice as the object of study, we constructed three models of VEST stents with different diameters and coupled them respectively to a model of the great saphenous vein graft, and numerically simulated the expansion-contraction process of the vein graft under the constraint of the stents to quantitatively evaluate the influence of stent size on the radial deformation and wall stress of the vein graft. The results showed that while the stent with a small diameter had a high restrictive effect in comparison with larger stents, it led to more severe concentration of wall stress and sharper changes in radial deformation along the axis of the graft, which may have adverse influence on the graft. In order to solve the aforementioned problems, we ameliorated the design of the stent by means of changing the cross-sectional shape of the thick and thin alloy wires from circle into rectangle and square, respectively, while keeping the cross-sectional areas of alloy wires and stent topology unchanged. Further numerical simulations demonstrated that the ameliorated stent evidently reduced the degrees of wall stress concentration and abrupt changes in radial deformation, which may help improve the biomechanical environment of the graft while maintaining the restrictive role of the stent.
Subject(s)
Alloys , Coronary Artery Bypass , Saphenous Vein/surgery , StentsABSTRACT
Objective To investigate the transport and deposition behaviors of lowdensity lipoproteins (LDL) in the carotid artery and explore their associations with hemodynamic and morphological factors, so as to provide theoretical references for assessing the risk and predisposing regions of atherosclerosis based on the characteristics and associated factors of LDL deposition at the carotid artery wall. Methods Subject-specific computational models of the carotid artery based on medical images from six healthy volunteers were built, and the transport and wall deposition of LDL under pulsatile flow conditions were simulated, and finally the correlations of wall LDL concentration and total area of regions with LDL concentration polarization with flow velocity and morphological parameters of the carotid artery were quantitatively analyzed. Results Regions with significant LDL deposition often appeared in carotid sinus near distal end of the common carotid artery, with the degree and spatial distribution of deposition differing considerably among subjects. The degree of LDL deposition was determined mainly by flow velocity, i.e., the lower the flow velocity was, the higher the degree of LDL deposition and accordingly the larger the area of wall regions with LDL concentration polarization was; whereas the spatial distribution of LDL deposition was significantly affected by morphological characteristics (especially bifurcation eccentricity ratio) of the carotid artery, for example, the distribution patterns could be divided into two typical types (i.e., circular distribution, unilateral distribution) according to bifurcation eccentricity ratio. Conclusions Flow velocity and morphological characteristics of the carotid artery are major factors determining respectively the degree and spatial distribution of LDL deposition, and therefore subject-specifically measuring these parameters will provide useful information for screening individuals at high risk of atherosclerosis or identifying atheroprone regions.
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Objective To investigate the transient hemodynamic changes during balloon deflation in coronary interventional operation, so as to explore the potential influence of balloon deflation on the occurrence of post-operative no-reflow. Methods An in vitro experimental apparatus was built, in which a high-speed camera was used to take snapshots of balloon deformation and flow field (marked by dyed water) during balloon deflation. Subsequently, image processing techniques were employed to derive the parameters of balloon deformation and estimate the flow velocity downstream from the balloon. A computer model of the experimental apparatus was constructed, with the incorporation of the measured balloon deformation data, to simulate the balloon deflation process under various perfusion pressure and fluid conditions. Results The balloon exhibited a highly nonlinear deformation behavior during deflation. The measured and simulated flow velocities downstream from the balloon were in reasonable agreement, both manifesting a monotonic increase with post-deflation time and perfusion pressure. Numerical simulations further revealed that when the flow velocity downstream from the balloon approached the physiological value of blood flow velocity in the coronary artery, the flow velocity in the balloon-vessel gap and wall shear stress (WSS) reached up to 8-10 times and 60-70 times of their physiological values, respectively. Conclusions Balloon deflation led to a sharp acceleration of flow in balloon-vessel gap and a concomitant abnormal rise in WSS, which might promote the stripping of plaque or thrombus flakes. In view of the fact that the balloon deflation-induced rise in WSS was augmented by the increase in perfusion pressure, taking strategies such as lowering pre-operative blood pressure or implementing balloon deflation during diastole in coronary interventional operation might help to reduce the risk of no-reflow.
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Objective:To explore predictive value of arterial velocity-pulse index (AVI) and arterial pressure-volume index (API) for early atherosclerosis (AS) in middle-aged population.Methods:A total of 138 middle-aged patients hospitalized in our hospital from May 2016 to Nov 2016 were enrolled.According to coronary angiography (CAG) outcomes, they were divided into AS group (n=86) and non-AS group (n=52).Before CAG, AVI, API and brachial-ankle pulse wave velocity (baPWV) were collected in two groups.General data and arterial stiffness indexes were compared between two groups, and the correlation among AVI, API, baPWV and general data were analyzed.Results:Compared with non-AS group, there were significant rise in AVI [(20.4±4.2) vs.(22.8±5.3)] and baPWV [(14.0±2.5) m/s vs.(16.3±3.0) m/s] in AS group,P<0.01 both.AVI was significant positively correlated with age, SBP, DBP, mean arterial pressure (MAP), pulse pressure (PP), API and baPWV (r=0.219~0.471, P<0.05 or <0.01);API was significant positively correlated with age, BMI, SBP, DBP, MAP, PP, brain natriuretic peptide (BNP), AVI and baPWV (r=0.213~0.726, P<0.05 or <0.01);baPWV was significant positively correlated with age, BMI, SBP, DBP, MAP, PP, AVI and API (r=0.201~0.472, P<0.05 or <0.01).Multi-factor linear regression analysis indicated that SBP was influencing factor for AVI (B=0.162,P=0.001), SBP, DBP and HDL-C were influencing factors for API (B=-0.166~2.146,P<0.05 or <0.01), SBP and HDL-C were influencing factors for baPWV (B=0.116,-3.009,P<0.01 both).Conclusion:Both elevated AVI and baPWV can predict atherosclerosis in middle-aged population
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Objective To use thrombelastography (TEG) and conventional coagulation tests (CCTs) to diagnose disseminated intravascular coagulation (DIC) and find a better diagnostic method.Methods Patients with potential DIC factors,DIC clinical manifestation or DIC patients suspected by laboratory tests were included after their admission into our hospital.TEGs and CCTs were detected,respectively.DIC score was evaluated.The single factor logistic regression was used to evaluate the correlation between TEG and CCTs as well as the diagnostic accuracy.Results The international normalized ratio (INR) in CCTs of the DIC patients were significantly higher,the reaction rime (R),clot formation time (K),angle rate of clot formation (α),maximum amplitude (MA),and composite index (CI) figures in TEG were significantly increased (P ＜ 0.05).The sensitivity and specificity of TEG were 82.4％,and 62.2％,which were significantly higher than 21.6％ and 47.2％ in CCTs (P ＜ 0.05).Single factor logistic regression results show that odd ratio (OR) in prothrombin time (PT) and INR of CCTs was 1.23 and 1.27,respectively.The OR in R,K,α,MA,and CI of TEG was 5.13,6.14,1.37,1.25,and 3.02,respectively.Conclusions Compared to CCTs,TEG is more indicative of the conditions of DIC patients and it might be a better way to predict the DIC risks,which is of greater value in clinical diagnosis.