The Effects of Micro-vessel Curvature Induced Elongational Flows on Platelet Adhesion

The emerging profile of blood flow and the cross-sectional distribution of blood cells have far reaching biological consequences in various diseases and vital internal processes, such as platelet adhesion. The effects of several essential blood flow parameters, such as red blood cell free layer width, wall shear rate, and hematocrit on platelet adhesion were previously explored to great lengths in straight geometries. In the current work, the effects of channel curvature on cellular blood flow are investigated by simulating the accurate cellular movement and interaction of red blood cells and platelets in a half-arc channel for multiple wall shear rate and hematocrit values. The results show significant differences in the emerging shear rate values and distributions between the inner and outer arc of the channel curve, while the cell distributions remain predominantly uninfluenced. The simulation predictions are also compared to experimental platelet adhesion in a similar curved geometry. The inner side of the arc shows elevated platelet adhesion intensity at high wall shear rate, which correlates with increased shear rate and shear rate gradient sites in the simulation. Furthermore, since the platelet availability for binding seems uninfluenced by the curvature, these effects might influence the binding mechanics rather than the probability. The presence of elongational flows is detected in the simulations and the link to increased platelet adhesion is discussed in the experimental results.

Assessment of the conjunctival microcirculation for patients presenting with acute myocardial infarction compared to healthy controls

Microcirculatory dysfunction occurs early in cardiovascular disease (CVD) development. Acute myocardial infarction (MI) is a late consequence of CVD. The conjunctival microcirculation is readily-accessible for quantitative assessment and has not previously been studied in MI patients. We compared the conjunctival microcirculation of acute MI patients and age/sex-matched healthy controls to determine if there were differences in microcirculatory parameters. We acquired images using an iPhone 6s and slit-lamp biomicroscope. Parameters measured included diameter, axial velocity, wall shear rate and blood volume flow. Results are for all vessels as they were not sub-classified into arterioles or venules. The conjunctival microcirculation was assessed in 56 controls and 59 inpatients with a presenting diagnosis of MI. Mean vessel diameter for the controls was 21.41 ± 7.57 μm compared to 22.32 ± 7.66 μm for the MI patients (p < 0.001). Axial velocity for the controls was 0.53 ± 0.15 mm/s compared to 0.49 ± 0.17 mm/s for the MI patients (p < 0.001). Wall shear rate was higher for controls than MI patients (162 ± 93 s−1 vs 145 ± 88 s−1, p < 0.001). Blood volume flow did not differ significantly for the controls and MI patients (153 ± 124 pl/s vs 154 ± 125 pl/s, p = 0.84). This pilot iPhone and slit-lamp assessment of the conjunctival microcirculation found lower axial velocity and wall shear rate in patients with acute MI. Further study is required to correlate these findings further and assess long-term outcomes in this patient group with a severe CVD phenotype.

CO2-Driven diffusiophoresis and water cleaning: similarity solutions for predicting the exclusion zone in a channel flow

We study diffusiophoretic exclusion zone (EZ) formation in rectangular channel flow, driven by CO2 dissolution from one side wall. By using a similarity transform and considering the flow structure, we obtain the relation between EZ and the wall shear rate.

Carotid Wall Shear Rate as a Marker of Systemic Atherosclerosis and Atherosclerotic Cardiovascular Disease

Aim: to assess possibility of the use of carotid wall shear rate (WSR) as a marker of systemic atherosclerosis and atherosclerotic cardiovascular disease (ASCVD).Materials and methods. We included into this study 200 patients with different cardiovascular risk (142 patients already had one or more ASCVD). All patients underwent ultrasound scanning of carotid and lower limb arteries with measurement of the ankle-brachial index. Carotid WSR was determined during ultrasonic scanning of carotid arteries in accordance with the Hagen-Poiseuille law.Results. Mean WSR value in this cohort of patients was 434±139 s–1. Based on the results of the ROCanalysis, it was found that WSR below the threshold value of 300 s–1 allowed to predict the presence of ASCVD with sensitivity of 97.1 % and specificity of 84.6 %. WSR <300 s–1 was associated with relative risk (RR) of ASCVD presence 11.2 (95 % CI 1.26–99.3, p=0.03), adjusted for factors such as sex, age, smoking, obesity, hypertension, estimated glomerular filtration rate (eGFR), low density lipoprotein cholesterol, and high sensitivity C-reactive protein, carotid intima-media thickness. The model which included carotid WSR, as well as factors such as the presence of type 2 diabetes, obesity, sex, age, eGFR, allowed to diagnose combined atherosclerotic lesions of peripheral arteries with a sensitivity of 73.1 % and a specificity of 90.3 %.Conclusion. Evaluation of the carotid WSR allows to diagnose with satisfactory sensitivity and specificity the presence of combined atherosclerosis of peripheral arteries and ASCVD.