Comparative Analyses of Blood Flow Through Mechanical Trileaflet and Bileaflet Aortic Valves

2021 ◽  
Author(s):  
Marek Pawlikowski ◽  
Anna Nieroda
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Flow Velocity ◽  
Circulatory System ◽  
Maximum Flow ◽  
Von Mises Stress ◽  
Effective Orifice Area ◽  
Aortic Valves ◽  
Orifice Area ◽  
Flow Through

Abstract The paper describes one of many issues concerning the human circulatory system. The simulation of blood flow through an artificial aortic heart valve using the finite element method (FEM) is the main subject of the paper. The studies aim to verify the performance of mechanical aortic valves of two types, i.e. bileaflet (BIL) and trileaflet (TRI) valves. The blood was modelled as Newtonian and non-Newtonian. Although the design of our TRI valve is preliminary and needs to be optimised, our results highlight some advances of such a valve geometry. This is manifested mainly by a central blood jet, contributing to more physiological blood flow and decreasing the risk of haemolysis. The central flow minimises the risk of leaflet dislocation. In addition, lower stresses extend the durability of the valve. However, the TRI valve geometry has also disadvantages, for instance, the occurrence of small peripheral streams or relatively low effective orifice area. The valves' performance was assessed by means of the reduced stress in the valves, the shear stress in the aortic wall, flow velocity field, and the effective orifice area. The maximum von Mises stress for the BIL valve leaflets is 0.3 MPa, and for the TRI valve: 0.06 MPa. The maximum flow velocity for the BIL valve is 4.52 m/s for 40° and for the TRI valve is 5.74 m/s. Higher shear stress is present in the BIL (151.5 Pa) than for the TRI valve (49.64 Pa).

scholarly journals Comparison of the hemodynamic parameters of transaortic blood flow in patients with aortic stenosis depending on the bicuspid or tricuspid valve structure

2020 ◽  
Vol 24 (4) ◽  
pp. 74-80
Author(s):  
V. V. Bazylev ◽  
R. M. Babukov ◽  
F. L. Bartosh ◽  
A. V. Gorshkova
Keyword(s):  
Blood Flow ◽  
Aortic Valve ◽  
Aortic Stenosis ◽  
Effective Area ◽  
Effective Orifice Area ◽  
Hemodynamic Parameters ◽  
Structure Comparison ◽  
Area Index ◽  
Orifice Area ◽  
Echocardiographic Study

Purpose: comparison of hemodynamic parameters of transaortic blood flow in patients with aortic stenosis depending on the bivalve or tricuspid structure of the aortic valve.Materials and methods. A study of 180 patients with isolated aortic valve stenosis (AC) with two – and threeleaf structure was conducted. Patients were ranked into 3 comparison subgroups by the area of the effective AC opening from 4 to 1.5 cm2; 1.5 to 1 cm2 and less than 1 cm2. An echocardiographic study was performed with the calculation of all the necessary parameters for the study.Results. The comparison subgroups were comparable in terms of effective orifice area (AVA), effective orifice area index (IAVA), body mass index (BMI), LV UO index, and LV FV (p > 0.05). However, the indicators Vmax, Gmean, and AT in patients with a bivalve AK structure in all comparison subgroups were significantly higher than in patients with a tricuspid structure. Comparison subgroup with AVA from 4 to 1.5 cm2: Vmax 2.8 ± 9 m/s and 2.5 ± 6 m/s p = 0.02. Gmean 18.6 ± 7.2 mm Hg and 15 ± 6 mm Hg p = 0.03, AT 82 ± 12 ms and 70 ± 10 ms p = 0.002. Comparison subgroup with AVA from 1.5 to 1 cm2: Vmax 3.7 ± 0.8 m/s and 3.5 ± 0.6 m/s p = 0.02. Average transaortic gradient 37 ± 10 mm Hg and 29 ± 5 mm Hg p = 0.04, AT 103 ± 11 ms and 94 ± 10 ms p = 0.02. Comparison subgroup with an effective area of less than 1 cm2: Vmax 5.7 ± 1.2 m/s and 4.7 ± 0.7 m/s p = 0.001, Gmean 54 ± 15 and 43 ± 11 mm Hg p < 0.001, AT 127 ± 20 ms and 112 ± 10 ms p = 0.002.Conclusion. Echocardiographic indicators of Vmax and Gmean in patients with bivalve AC structure have higher values than in patients with tricuspid AC structure with a comparable opening area.

Studies on Pulsed-wave Doppler Echocardiographic Parameters of Blood Flow through Mitral, Tricuspid and Aortic Valves in Healthy Indian Spitz Dogs

2021 ◽  
Author(s):  
Deepti Bodh ◽  
Mozammel Hoque ◽  
Abhishek Chandra Saxena
Keyword(s):  
Blood Flow ◽  
Wave Velocity ◽  
Doppler Echocardiography ◽  
Aortic Valves ◽  
Velocity Time Integral ◽  
Wave Velocities ◽  
Time Integral ◽  
Pulsed Wave Doppler ◽  
Flow Through ◽  
Isovolumic Relaxation

Background: Pulsed-wave Doppler measures blood flow at specific point and provides information on velocity, direction and uniformity of blood flow throughout cardiac cycle. Till date, there is no published data on study of cardiac parameters using pulsed-wave Doppler echocardiography in Indian Spitz dogs.Methods: Twenty-four clinically normal Indian Spitz dogs were subjected to pulsed-wave Doppler echocardiography to determine the reference intervals for Doppler parameters of blood flow through mitral, tricuspid and aortic valves. Mitral peak E and A-wave velocities, E/A ratio, deceleration time, isovolumic relaxation time, E and A-wave velocity time integral, E duration and A duration were 0.69±0.09 m/s, 0.43±0.12 m/s, 1.69±0.45, 111.25±35.94 ms, 48.50±24.77 ms, 0.07±0.01 m and 0.04±0.02 m, 196.88±44.38 ms and 181.25±64.89 ms, respectively. Tricuspid peak E and A-wave velocities, E/A ratio and E and A-wave velocity time integral were 0.57±0.11 m/s, 0.38±0.08 m/s, 1.56±0.32 and 0.07±0.02 m and 0.05±0.01 m, respectively. Aortic peak velocity, velocity time integral and ejection time were 0.87±0.07 m/s, 0.11±0.02 m and 0.25±0.04 s, respectively. Conclusion: The reference values of flow parameters across mitral, tricuspid and aortic valves using pulsed-wave Doppler echocardiography were determined. Mitral, tricuspid and aortic valve flow variables were unaffected by gender whereas isovolumic relaxation correlated positively with body weight.

A Theoretical Description of Blood Flow Through the Mitral Orifice

1989 ◽  
Vol 111 (2) ◽  
pp. 141-146 ◽  
Author(s):  
D. M. Bakalyar ◽  
A. M. Hauser ◽  
G. C. Timmis
Keyword(s):  
Blood Flow ◽  
Velocity Profile ◽  
Theoretical Description ◽  
Doppler Velocity ◽  
Comprehensive Model ◽  
Orifice Area ◽  
Ventricular Mechanics ◽  
Straight Line ◽  
Mitral Orifice ◽  
Flow Through

A nonlinear differential equation describing the Doppler velocity profile for blood flow through the mitral valve has been derived. This equation is based on fluid dynamics and a simple, but comprehensive model of atrial and ventricular mechanics. A numerical solution to the equation is described and provides excellent agreement with Doppler velocity curves obtained clinically. One important result of the theory is that in patients with mitral stenosis, the slope of the clinically observed straight-line descent of the velocity profile is proportional to the mitral orifice area and inversely proportional to the atrioventricular compliance.

Mathematical analysis of Phan-Thien–Tanner fluid model for blood in arteries

2015 ◽  
Vol 08 (05) ◽  
pp. 1550064
Author(s):  
Noreen Sher Akbar ◽  
S. Nadeem
Keyword(s):  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Fluid Model ◽  
Shearing Stress ◽  
Small Arteries ◽  
Tapered Artery ◽  
Impedance Wall ◽  
Flow Through ◽  
Parameters Of Interest

In the present paper, we have studied the blood flow through tapered artery with a stenosis. The non-Newtonian nature of blood in small arteries is analyzed mathematically by considering the blood as Phan-Thien–Tanner fluid. The representation for the blood flow is through an axially non-symmetrical but radially symmetric stenosis. Symmetry of the distribution of the wall shearing stress and resistive impedance and their growth with the developing stenosis is another important feature of our analysis. Exact solutions have been evaluated for velocity, resistance impedance, wall shear stress and shearing stress at the stenosis throat. The graphical results of different type of tapered arteries (i.e. converging tapering, diverging tapering, non-tapered artery) have been examined for different parameters of interest.

Microvascular dilation in response to occlusion: a coordinating role for conducted vasomotor responses

2000 ◽  
Vol 279 (1) ◽  
pp. H279-H284 ◽  
Author(s):  
Kim A. Dora ◽  
David N. Damon ◽  
Brian R. Duling
Keyword(s):  
Endothelial Cells ◽  
Blood Flow ◽  
Shear Stress ◽  
Smooth Muscle ◽  
Third Order ◽  
Vasomotor Responses ◽  
Vasodilatory Response ◽  
Flow Through ◽  
Stress Dependent ◽  
Dependent Mechanism

In rat cremasteric microcirculation, mechanical occlusion of one branch of an arteriolar bifurcation causes an increase in flow and vasodilation of the unoccluded daughter branch. This dilation has been attributed to the operation of a shear stress-dependent mechanism in the microcirculation. Instead of or in addition to this, we hypothesized that the dilation observed during occlusion is the result of a conducted signal originating distal to the occlusion. To test this hypothesis, we blocked the ascending spread of conducted vasomotor responses by damaging the smooth muscle and endothelial cells in a 200-μm segment of second- or third-order arterioles. We found that a conduction blockade eliminated or diminished the occlusion-associated increase in flow through the unoccluded branch and abolished or strongly attenuated the vasodilatory response in both vessels at the branch. We also noted that vasodilations induced by ACh (10−4 M, 0.6 s) spread to, but not beyond, the area of damage. Taken together, these data provide strong evidence that conducted vasomotor responses have an important role in coordinating blood flow in response to an arteriolar occlusion.

Pulsatile Blood Flow Through a Constricted Porous Artery

2020 ◽  
Vol 17 (2) ◽  
pp. 743-749
Author(s):  
Salah Uddin ◽  
Obaid Ullah Mehmood ◽  
Mahathir Mohamad ◽  
Mahmod Abd Hakim Mohmad ◽  
D. F. Jamil ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Blood Flow ◽  
Flow Velocity ◽  
Nonlinear Differential Equations ◽  
Fluid Velocity ◽  
Volumetric Flow Rate ◽  
Physical Parameters ◽  
Porosity Parameter ◽  
Arterial Blood ◽  
Flow Through

In this paper a speculative study of an incompressible Newtonian blood flow through a constricted porous channel and pulsatile nature is inspected. Porosity parameter λ is incorporated in the momentum equation. Governing nonlinear differential equations are numerically evaluated by employing the perturbation method technique for a very small perturbation parameter ε 1 such that ε ≠ 0 and with conformable boundary conditions. Numerical results of the flow velocity profile and volumetric flow rate have been derived numerically and detailed graphical analysis for different physical parameters porosity, Reynolds number and stenosis has been presented. It is found that arterial blood velocity is dependent upon all of these factors and that the relationship of fluid velocity and flow is more complex and nonlinear than heretofore generally believe. Furthermore the flow velocity enhanced with Reynolds number, porosity parameter and at maximum position of the stenosis/constriction.

MATHEMATICAL MODELING OF BLOOD FLOW IN A POROUS VESSEL HAVING DOUBLE STENOSES IN THE PRESENCE OF AN EXTERNAL MAGNETIC FIELD

2011 ◽  
Vol 04 (02) ◽  
pp. 207-225 ◽  
Author(s):  
J. C. MISRA ◽  
A. SINHA ◽  
G. C. SHIT
Keyword(s):  
Mathematical Modeling ◽  
Magnetic Field ◽  
Mathematical Model ◽  
Blood Flow ◽  
Shear Stress ◽  
External Magnetic Field ◽  
Volumetric Flow Rate ◽  
Hematocrit Level ◽  
Flow Through ◽  
The Mathematical Model

In this paper, a mathematical model has been developed for studying blood flow through a porous vessel with a pair of stenoses under the action of an externally applied magnetic field. Blood flowing through the artery is considered to be Newtonian. This model is consistent with the principles of ferro-hydrodynamics and magnetohydrodynamics. Expressions for the velocity profile, volumetric flow rate, wall shear stress and pressure gradient have been derived analytically under the purview of the model. The above said quantities are computed for a specific set of values of the different parameters involved in the model analysis. This serves as an illustration of the validity of the mathematical model developed here. The results estimated on the basis of the computation are presented graphically. The obtained results for different values of the parameters involved in the problem under consideration, show that the flow is appreciably influenced by the presence of magnetic field and the rise in the hematocrit level.

Stentless versus Stented Bioprosthetic Aortic Valves

2009 ◽  
Vol 4 (2) ◽  
pp. 61-73 ◽  
Author(s):  
Davy Cheng ◽  
John Pepper ◽  
Janet Martin ◽  
Rex Stanbridge ◽  
Francis D. Ferdinand ◽  
...  
Keyword(s):  
Aortic Valve ◽  
Controlled Trial ◽  
Meta Analysis ◽  
Effective Orifice Area ◽  
Aortic Valves ◽  
Area Index ◽  
Orifice Area ◽  
Mean Differences ◽  
Bioprosthetic Valves

Objective This meta-analysis sought to determine whether stentless bioprosthetic valves improve clinical and resource outcomes compared with stented valves in patients undergoing aortic valve replacement. Methods A comprehensive search was undertaken to identify all randomized and nonrandomized controlled trials comparing stentless to stented bioprosthetic valves in patients undergoing aortic valve replacement available up to March 2008. The primary outcomes were clinical and resource outcomes in randomized controlled trial (RCT). Secondary outcomes clinical and resource outcomes in nonrandomized controlled trial (non-RCT). Odds ratios (OR), weighted mean differences (WMD), or standardized mean differences and their 95% confidence intervals (CI) were analyzed as appropriate. Results Seventeen RCTs published in 23 articles involving 1317 patients, and 14 non-RCTs published in 18 articles involving 2485 patients were included in the meta-analysis. For the primary analysis of randomized trials, mortality for stentless versus stented valve groups did not differ at 30 days (OR 1.36, 95% CI 0.68–2.72), 1 year (OR 1.01, 95% CI 0.55–1.85), or 2 to 10 years follow-up (OR 0.82, 95% CI 0.50–1.33). Aggregate event rates for all-cause mortality at 30 days were 3.7% versus 2.9%, at 1 year were 5.5% versus 5.9% and at 2 to 10 years were 17% versus 19% for stentless versus stented valve groups, respectively. Stroke or neurologic complications did not differ between stentless (3.6%) and stented (4.0%) valve groups. Risk of prosthesis-patient mismatch was numerically lower in the stentless group (11.0% vs. 31.3%, OR 0.30, 95% CI 0.05–1.66), but this parameter was reported in few trials and did not reach statistical significance. Effective orifice area index was significantly greater for stentless aortic valve compared with stented valves at 30 days (WMD 0.12 cm2/m2), at 2 to 6 months (WMD 0.15 cm2/m2), and at 1 year (WMD 0.26 cm2/m2). Mean gradient at 1 month was significantly lower in the stentless valve group (WMD −6 mm Hg), at 2 to 6 month follow-up (WMD −4 mm Hg,), at 1 year follow-up (WMD −3 mm Hg) and up to 3 year follow-up (WMD −3 mm Hg) compared with the stented valve group. Although the left ventricular mass index was generally lower in the stentless group versus the stented valve group, the aggregate estimates of mean difference did not reach significance during any time period of follow-up (1 month, 2–6 months, 1 year, and 8 years). Conclusions Evidence from randomized trials shows that subcoronary stentless aortic valves improve hemodynamic parameters of effective orifice area index, mean gradient, and peak gradient over the short and long term. These improvements have not led to proven impact on patient morbidity, mortality, and resource-related outcomes; however, few trials reported on clinical outcomes beyond 1 year and definitive conclusions are not possible until sufficient evidence addresses longer-term effects.

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