Impact of strut dimensions and vessel caliber on thrombosis risk of bioresorbable scaffolds using hemodynamic metrics

2019 ◽  
Vol 64 (3) ◽  
pp. 251-262 ◽  
Author(s):  
Michael Stiehm ◽  
Carolin Wüstenhagen ◽  
Stefan Siewert ◽  
Hüseyin Ince ◽  
Niels Grabow ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Effective Diffusion ◽  
Coronary Vessels ◽  
Vessel Diameter ◽  
Sensitivity Analyses ◽  
Related Factor ◽  
Vessel Size ◽  
Bioresorbable Scaffolds ◽  
Thrombosis Risk ◽  
Computational Fluid Dynamics Cfd

AbstractBioresorbable scaffolds (BRS) promise to be the treatment of choice for stenosed coronary vessels. But higher thrombosis risk found in current clinical studies limits the expectations. Three hemodynamic metrics are introduced to evaluate the thrombosis risk of coronary stents/scaffolds using transient computational fluid dynamics (CFD). The principal phenomena are platelet activation and effective diffusion (platelet shear number, PSN), convective platelet transport (platelet convection number, PCN) and platelet aggregation (platelet aggregation number, PAN) were taken into consideration. In the present study, two different stent designs (thick-strut vs. thin-strut design) positioned in small- and medium-sized vessels (reference vessel diameter, RVD=2.25 mm vs. 2.70 mm) were analyzed. In both vessel models, the thick-strut design induced higher PSN, PCN and PAN values than the thin-strut design (thick-strut vs. thin-strut: PSN=2.92/2.19 and 0.54/0.30; PCN=3.14/1.15 and 2.08/0.43; PAN: 14.76/8.19 and 20.03/10.18 for RVD=2.25 mm and 2.70 mm). PSN and PCN are increased by the reduction of the vessel size (PSN: RVD=2.25 mm vs. 2.70 mm=5.41 and 7.30; PCN: RVD=2.25 mm vs. 2.70 mm=1.51 and 2.67 for thick-strut and thin-strut designs). The results suggest that bulky stents implanted in small caliber vessels may substantially increase the thrombosis risk. Moreover, sensitivity analyses imply that PSN is mostly influenced by vessel size (lesion-related factor), whereas PCN and PAN sensitively respond to strut-thickness (device-related factor).

Oxygen consumption of pial arteries

1979 ◽  
Vol 236 (1) ◽  
pp. H151-H156 ◽  
Author(s):  
R. M. Navari ◽  
E. P. Wei ◽  
H. A. Kontos ◽  
J. L. Patterson
Keyword(s):  
Smooth Muscle ◽  
Oxygen Consumption ◽  
Parietal Cortex ◽  
Vessel Wall ◽  
Vessel Diameter ◽  
Progressive Decrease ◽  
Pial Arteries ◽  
Vessel Size ◽  
Size Dependent ◽  
Pial Arterioles

Pial arterioles and arteries, normally responsive to alterations in PaCO2, were obtained by microdissection from the parietal cortex of 53 anesthetized cats. The oxygen consumption of these vessels, determined with the Cartesian diver microrespirometer, was found to be size dependent. It increased progressively from vessels 60 mum in diameter to vessels 250 mum in diameter. In vessels 250--375 mum in diameter there was a progressive decrease in oxygen consumption with increasing vessel size. The oxygen consumption was not altered by increasing the oxygen concentration in the diver from 20% to 95%, or that of glucose from 1.1 to 2.0 mM. Planimetry of histological sections showed that the percentage of endothelium and smooth muscle increased as vessel diameter increased from 60 to 200 mum, and thereafter decreased with increasing vessel size. When these differences in the composition of the vessel wall were taken into account, there was still residual dependence of the oxygen consumption on vessel diameter. This may represent intrinsic differences in the metabolic rate of vascular smooth muscle in vessels of different size.

Chronic systemic delivery of angiopoietin-2 reveals a possible independent angiogenic effect

2006 ◽  
Vol 291 (2) ◽  
pp. H948-H956 ◽  
Author(s):  
W. Bureau ◽  
P. Van Slyke ◽  
J. Jones ◽  
R. N. N. Han ◽  
Nicole L. Ward ◽  
...  
Keyword(s):  
Vascular Remodeling ◽  
Coronary Vessels ◽  
Vessel Diameter ◽  
Systemic Delivery ◽  
Vegf Expression ◽  
Vascular Abnormalities ◽  
Vessel Remodeling ◽  
Angiogenic Effect ◽  
Angiopoietin 2 ◽  
Circulating Levels

Angiopoietin-2 has been implicated in the angiogenic response; however, this response has been tied to the expression of VEGF, and an independent angiogenic role has yet to be described. In this report, we detail the generation of transgenic mice that conditionally express angiopoietin-2 in the liver, resulting in sustained increases in circulating levels. These animals survive gestation and present with several vascular abnormalities, including an increase in the diameter of myocardial coronary vessels and a reduction in the density of endocardial vessels. In the lung, prominent increases in vessel diameter were observed. These vascular remodeling changes occurred in the absence of any apparent increase in VEGF expression. Our results illustrate that chronic systemic delivery of angiopoietin-2 induces angiogenesis in the absence of increased VEGF expression and that angiopoietin-2 promotes myocardial coronary vessel remodeling.

Two-Dimensional Pore Pressure Distribution Model to Evaluate Effects of Shale Semipermeable Membrane Characteristics

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Jia Wei ◽  
Yuanfang Cheng ◽  
Chuanliang Yan
Keyword(s):  
Diffusion Coefficient ◽  
Pressure Distribution ◽  
Pore Pressure ◽  
Effective Diffusion Coefficient ◽  
Early Stage ◽  
Drilling Fluid ◽  
Effective Diffusion ◽  
Solute Diffusion ◽  
Sensitivity Analyses ◽  
Distribution Model

During the drilling of shale formations, drilling fluids can intrude into the wellbore, raise the pore pressure, and lead to wellbore instability. Based on the thermodynamic theory, a new model was established to calculate pore pressure. The model considers the effects of solute diffusion and solution convection and conducts sensitivity analyses. The results show that the drilling fluid activity significantly affects the pore pressure distribution. The pore pressure under high drilling fluid activity will increase rapidly in the early stage. Low drilling fluid activity can effectively suppress the growth of pore pressure. And a low effective diffusion coefficient of solute and a high membrane efficiency also help to reduce pore pressure. Therefore, reducing drilling fluid activity should be conducted in priority in drilling fluid design. Lowering its solute effective diffusion coefficient and increasing its viscosity can also be considered as auxiliary methods.

Vasomotion in cerebral microcirculation of awake rabbits

1988 ◽  
Vol 254 (1) ◽  
pp. H67-H71 ◽  
Author(s):  
W. G. Hundley ◽  
G. J. Renaldo ◽  
J. E. Levasseur ◽  
H. A. Kontos
Keyword(s):  
Inverse Relationship ◽  
Mean Amplitude ◽  
Average Frequency ◽  
Vessel Diameter ◽  
Cerebral Microcirculation ◽  
Vessel Size ◽  
Local Factors ◽  
Arterial Blood ◽  
Cerebral Arterioles ◽  
The Mean

Cerebral arterioles of unanesthetized rabbits equipped with chronically implanted cranial windows exhibited spontaneous rhythmic variation in vessel caliber characteristic of vasomotion. This variation was noted in all examined vessels. The vasomotion was independent of arterial blood pressure or respiration. The average frequency was 0.74 cycles/min and was independent of vessel size. The mean amplitude of the oscillations had a statistically significant inverse relationship to vessel diameter (r = 0.69). Vasodilation induced by arterial hypercapnia, topical adenosine, or topical acetylcholine had no significant effect on the frequency or amplitude of vasomotion. Anesthesia significantly reduced the frequency in arterioles of all sizes and markedly reduced amplitude in large arterioles. Topical verapamil resulted in a statistically significant reduction in frequency and in peak amplitude. Variations in vessel diameter occurred simultaneously in arterioles and their companion venules. We conclude that the cerebral microcirculation displays active vasomotion, which is significantly depressed by anesthesia or topical verapamil. The results also suggest that vasomotion is probably controlled by local factors.

scholarly journals Experimental Investigation and CFD Modeling of Supercritical Adsorption Process

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 1957
Author(s):  
Artem Lebedev ◽  
Daria Lovskaya ◽  
Natalia Menshutina
Keyword(s):  
Active Substance ◽  
Adsorption Process ◽  
Effective Diffusion ◽  
Cfd Modeling ◽  
Proposed Model ◽  
Structure Of Flow ◽  
Supercritical Adsorption ◽  
Mass Transport Rate ◽  
Computational Fluid Dynamics Cfd ◽  
Temperature And Pressure

The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure.

scholarly journals AngioNet: a convolutional neural network for vessel segmentation in X-ray angiography

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kritika Iyer ◽  
Cyrus P. Najarian ◽  
Aya A. Fattah ◽  
Christopher J. Arthurs ◽  
S. M. Reza Soroushmehr ◽  
...  
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Coronary Vessels ◽  
Quantitative Coronary Angiography ◽  
Vessel Diameter ◽  
Vessel Segmentation ◽  
Clinical Workflow ◽  
X Ray ◽  
Multiple Network ◽  
Diameter Reduction

AbstractCoronary Artery Disease (CAD) is commonly diagnosed using X-ray angiography, in which images are taken as radio-opaque dye is flushed through the coronary vessels to visualize the severity of vessel narrowing, or stenosis. Cardiologists typically use visual estimation to approximate the percent diameter reduction of the stenosis, and this directs therapies like stent placement. A fully automatic method to segment the vessels would eliminate potential subjectivity and provide a quantitative and systematic measurement of diameter reduction. Here, we have designed a convolutional neural network, AngioNet, for vessel segmentation in X-ray angiography images. The main innovation in this network is the introduction of an Angiographic Processing Network (APN) which significantly improves segmentation performance on multiple network backbones, with the best performance using Deeplabv3+ (Dice score 0.864, pixel accuracy 0.983, sensitivity 0.918, specificity 0.987). The purpose of the APN is to create an end-to-end pipeline for image pre-processing and segmentation, learning the best possible pre-processing filters to improve segmentation. We have also demonstrated the interchangeability of our network in measuring vessel diameter with Quantitative Coronary Angiography. Our results indicate that AngioNet is a powerful tool for automatic angiographic vessel segmentation that could facilitate systematic anatomical assessment of coronary stenosis in the clinical workflow.

Abstract 6256: Absence of Leptin Resistance in Platelets from Obese Individuals Suggests a Mechanism for Increased Thrombosis Risk in Obesity

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Claudia Dellas ◽  
Katrin Schaefer ◽  
Ilonka Rohm ◽  
Mareike Lankeit ◽  
Gerd Hasenfuss ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Normal Weight ◽  
The Body ◽  
Leptin Resistance ◽  
Morbidly Obese ◽  
Thrombosis Risk ◽  
Obese Subjects ◽  
Plasma Leptin ◽  
And Control ◽  
Induced Aggregation

Clinical studies have demonstrated that elevated leptin levels, such as frequently found in obesity, are an independent cardiovascular risk factor. We and others have shown that leptin promotes platelet aggregation and thrombosis. However, little is known about the existence of platelet resistance to leptin, particularly in the setting of obesity and central leptin resistance. In the present study, we examined the effects of leptin on platelet aggregation in morbidly obese subjects (n=40; BMI 41.6±1.1 kg/m2; leptin 49.7±3.4 ng/mL) in comparison to normal-weight controls (n=36; BMI 23.3±0.4; leptin 6.5±0.7). The aggregatory response to ADP was significantly increased in platelets from obese donors compared to controls as shown by a left-shift in the ADP dose curves. Thus, percent platelet aggregation at 2, 3, 4, and 5 μM ADP was 18.7±4.8 in the obese vs. 4.7±2.0 in controls (P=0.01), 37.2±6.6 vs. 17.1±4.4 (P=0.01), 60.8±6.0 vs. 37.8±6.5 (P=0.01), and 80.2±6.5 vs. 44.5±8.8 (P=0.002), respectively. Plasma leptin levels, but not the body-mass-index, were significantly higher in subjects with stronger (above the median) platelet aggregation in response to ADP compared to those with weaker (below the median) aggregation (35.9±5.1 vs. 22.4±4.1 ng/mL; P=0.04). In further experiments, exogenous leptin stimulation promoted ADP-induced platelet aggregation by 25% on average, and there was no difference in the responsiveness to leptin between platelets from obese and those from lean donors (controls; P=0.99). Using Western blot analysis we found that leptin induced phosphorylation of the signaling molecules JAK2 and STAT3 to a similar extent in platelets from both groups. Expression of potential mediators of leptin resistance (SOCS3 and PTP1B) also did not differ in platelets from obese and control subjects. Taken together, our data indicate that platelets from obese donors show increased aggregatory response to ADP, which might partly result from the increased circulating leptin levels. Platelets from obese individuals were not resistant to the enhancing effects of leptin on ADP-induced aggregation. Our results thus support the existence of a direct link between obesity, hyperleptinemia and thrombosis.

Lu 23051, A New Potent Inhibitor Of Platelet Aggregation

1981 ◽  
Author(s):  
H D Lehmann ◽  
J Gries ◽  
D Lenke
Keyword(s):  
Platelet Aggregation ◽  
Ex Vivo ◽  
Platelet Rich Plasma ◽  
Coronary Vessels ◽  
Inhibitory Effect ◽  
Spontaneously Hypertensive ◽  
Dependent Inhibition ◽  
Induced Aggregation

6- [p-(2-(Chiorpropionylamino)phenyl] -4.5-dihydro-5-methyl-3(2H)-pyridazinone, LU 23051, is primarily characterized by its strong inhibition of platelet aggregation under in vitro and in vivo conditions. In vitro there is a concentration-dependent inhibition of ADP and collagen induced aggregation in platelet rich plasma of man, rat and dog. The inhibitory concentration EC 33 % is 0.0010-0.030 mg/1 (man: ADP-0.030, col 1.-0.013 mg/l) depending on species and type of aggregation. When administered orally in ex vivo experiments on rats and dogs the substance is found to have a dose-dependent antiaggregatory effect in the range from 0.1-3.16 mg/kg. The ED 33 % is 0.27-0.63 mg/kg.-In addition after oral administration the substance has a good inhibitory effect in models being based on intravascular platelet aggregation. Thus, a dose of 1 mg/kg inhibits laser-induced aggregation in mesenteric venules of rats. Mortality after i.v. injection of collagen in mice is reduced by 50 % after a dose of 0.02 mg/kg. A dose of 0.039 mg/kg prolongs the bleeding time of rats by 50 %. The aggregation-inhibiting action is of long duration (0.1 mg/kg p.o.∼24 h). The substance does not interfere with clotting.Besides its effect on platelet aggregation LU 23051 acts as vasodilatator as well. Dilatation of coronary vessels by 100 % is seen in isolated guinea-pig hearts at a concentration of 0.1 mg/l. In spontaneously hypertensive rats the substance has an anti hypertensive effect. The ED 20 % is 0.36 mg/kg p.o.The combination of antiaggregatory and vasodilatatory effects opens up interesting aspects with respect to the pharmacotherapeutic use of the new substance

Comparative use of turkey and chicken wing brachial artery models for microvascular anastomosis training

2011 ◽  
Vol 115 (6) ◽  
pp. 1231-1235 ◽  
Author(s):  
Adib A. Abla ◽  
Timothy Uschold ◽  
Mark C. Preul ◽  
Joseph M. Zabramski
Keyword(s):  
Brachial Artery ◽  
Training Model ◽  
Vessel Diameter ◽  
Microvascular Anastomosis ◽  
Initial Model ◽  
Vessel Size ◽  
Training Models ◽  
Wing Model ◽  
Practice Models ◽  
Equidistant Points

Object The aim of this study was to describe a turkey wing model for microvascular anastomosis training and compare it to the previously outlined chicken wing model. Methods The authors compared diameter measurements in each of 5 turkey and 5 chicken brachial arteries at 3 equidistant points. Usable vessel length was measured (from joint to joint) in each of the specimens. A survey was created and distributed at a bypass training course to assess the attendees' impressions of various practice models used for bypass. Results The turkey wing brachial artery was consistently larger in diameter (p < 0.01) and longer (p < 0.01) than the chicken wing artery and showed less variability in the vessel diameter (1.47 ± 0.14 mm in the turkey vs 1.07 ± 0.25 mm in the chicken). In a survey of 15 bypass course participants, the live rat training model scored highest overall and was ranked as the best model for training; however, the turkey wing model was ranked second best and was consistently scored ahead of the chicken wing and silastic tube training models. Conclusions The authors' institutional preference has shifted to the use of a turkey wing artery as the initial model for microanastomosis training. Advantages in terms of vessel size and tissue durability favor this model over the chicken wing as part of a graduated instruction process.

DIMETHYL SULFOXIDE INHIBITS PLATELET AGGREGATION IN PARTIALLY OBSTRUCTED CANINE CORONARY VESSELS

1983 ◽  
Vol 411 (1 Biological Ac) ◽  
pp. 352-356 ◽  
Author(s):  
Daniel G. Pace ◽  
John L. Kovacs ◽  
Larry R. Klevans
Keyword(s):  
Platelet Aggregation ◽  
Dimethyl Sulfoxide ◽  
Coronary Vessels
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