scholarly journals Evaluation of prosthetic-valved devices by means of numerical simulations

2011 ◽  
Vol 369 (1945) ◽  
pp. 2502-2509 ◽  
Author(s):  
M. D. de Tullio ◽  
G. Pascazio ◽  
L. Weltert ◽  
R. De Paulis ◽  
R. Verzicco
Keyword(s):  
Cardiac Cycle ◽  
Suture Line ◽  
Flow Dynamics ◽  
Device Performance ◽  
Prosthetic Device ◽  
Vortical Structures ◽  
Structure Dynamics ◽  
Blood Flow Dynamics

The in vivo evaluation of prosthetic device performance is often difficult, if not impossible. In particular, in order to deal with potential problems such as thrombosis, haemolysis, etc., which could arise when a patient undergoes heart valve replacement, a thorough understanding of the blood flow dynamics inside the devices interacting with natural or composite tissues is required. Numerical simulation, combining both computational fluid and structure dynamics, could provide detailed information on such complex problems. In this work, a numerical investigation of the mechanics of two composite aortic prostheses during a cardiac cycle is presented. The numerical tool presented is able to reproduce accurately the flow and structure dynamics of the prostheses. The analysis shows that the vortical structures forming inside the two different grafts do not influence the kinematics of a bileaflet valve or the main coronary flow, whereas major differences are present for the stress status near the suture line of the coronaries to the prostheses. The results are in agreement with in vitro and in vivo observations found in literature.

PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
Matthew D. Ford ◽  
Hristo N. Nikolov ◽  
Jaques S. Milner ◽  
Stephen P. Lownie ◽  
Edwin M. DeMont ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Cardiac Cycle ◽  
Flow Dynamics ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Cfd Simulations ◽  
Flow Through

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.

Emerging Vascular Applications of Magnetic Resonance Imaging: A Picture is Worth More than a Thousand Words

Vascular ◽  
2006 ◽  
Vol 14 (6) ◽  
pp. 366-371 ◽  
Author(s):  
Tamara N. Fitzgerald ◽  
Akihito Muto ◽  
Fabio Akimaro Kudo ◽  
Jose Mario Pimiento ◽  
Robert Todd Constable ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Three Dimensional ◽  
Quantitative Information ◽  
Data Set ◽  
Vascular Intervention ◽  
In Vivo Experiments ◽  
Blood Flow Dynamics

Vascular applications of magnetic resonance (MR) imaging are reviewed, with emphasis on algorithms that use nonpictorial information contained in the MR data set. Current clinical vascular practice generally limits use of MR angiography and three-dimensional vessel images to qualitative pictorial rendering without routinely using the available quantitative information contained within the MR data. This review is dedicated to recent advances that include characterization of vessel histology, assessment of carotid plaque vulnerability, characterization of blood flow dynamics, quantitative analysis of disease severity, and prediction of vascular intervention outcome. Examples from histologic preparation, in vitro and in vivo experiments, are discussed, with an emphasis on potential clinical applications and advances in acquisition technology.

Transmural distribution of intramyocardial pressure measured by micropipette technique

1985 ◽  
Vol 249 (6) ◽  
pp. H1216-H1223 ◽  
Author(s):  
F. W. Heineman ◽  
J. Grayson
Keyword(s):  
Cardiac Cycle ◽  
Regression Line ◽  
Cardiac Performance ◽  
Aortic Constriction ◽  
Response Characteristics ◽  
Intramyocardial Pressure ◽  
In Vitro Response ◽  
Dynamic Response Characteristics

A technique is presented for measuring intramyocardial pressure (IMP) in beating hearts using the servo-nulling pressure transducer equipped with polyethylene micropipettes (ID less than 12 micron). The static and dynamic response characteristics of the system were tested in a pressurized, saline-filled container as well as in a pressurized, hollow, gelatin cylinder. The system was then used to measure IMP in vivo in the hearts of 12 dogs during stable cardiac performance and with aortic constriction. In vitro response characteristics were found to be satisfactory for accurate reproduction of cardiovascular waveforms. Peak systolic IMP was not found to exceed the simultaneously recorded left intraventricular pressure (LVP). Furthermore, the slope of the regression line relating the IMP to LVP during systole is linearly related (slope 0.98) to the depth of the micropipette tip in the ventricular wall, as normalized to total wall thickness. Diastolic IMP ranged between 1 +/- 1 (minimum during the cardiac cycle) and 4 +/- 2 mmHg (end diastolic) at associated LVP of 2 +/- 2 and 5 +/- 2 mmHg (mean +/- SD), respectively.

scholarly journals Frequency modulation of renal myogenic autoregulation by perfusion pressure

2007 ◽  
Vol 293 (3) ◽  
pp. R1199-R1204 ◽  
Author(s):  
Xuemei Wang ◽  
Rodger D. Loutzenhiser ◽  
William A. Cupples
Keyword(s):  
Perfusion Pressure ◽  
Function Analysis ◽  
Renal Perfusion ◽  
Tubuloglomerular Feedback ◽  
Operating Frequency ◽  
Systemic Injection ◽  
Transfer Function Analysis ◽  
Blood Flow Dynamics

Recent studies of renal autoregulation have shown modulation of the faster myogenic mechanism by the slower tubuloglomerular feedback and that the modulation can be detected in the dynamics of the myogenic mechanism. Conceptual and empirical considerations suggest that perfusion pressure may modulate the myogenic mechanism, although this has not been tested to date. Here we present data showing that the myogenic operating frequency, assessed by transfer-function analysis, varied directly as a function of perfusion pressure in the hydronephrotic kidney perfused in vitro over the range from 80 to 140 mmHg. A similar result was obtained in intact kidneys in vivo when renal perfusion pressure was altered by systemic injection of NG-nitro-l-arginine methyl ester (l-NAME). When perfusion pressure was not allowed to increase, l-NAME did not affect the myogenic operating frequency despite equivalent reduction of renal vascular conductance. Blood-flow dynamics were assessed in the superior mesenteric artery before and after l-NAME. In this vascular bed, the operating frequency of the myogenic mechanism was not affected by perfusion pressure. Thus the operating frequency of the renal myogenic mechanism is modulated by perfusion pressure independently of tubuloglomerular feedback, and the data suggest some degree of renal specificity of this response.

scholarly journals Investigation of the Pressure and Flow Dynamics during Aspiration Thrombectomy: A Mathematical Modelling Study

2021 ◽  
Vol 2071 (1) ◽  
pp. 012023
Author(s):  
Riccardo Marconi ◽  
Ying Yang ◽  
Shailesh Naire
Keyword(s):  
Blood Flow ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Interventional Procedure ◽  
Blood Clot ◽  
Flow Dynamics ◽  
Collateral Flow ◽  
Aspiration Thrombectomy ◽  
Blood Flow Dynamics

Abstract Aspiration thrombectomy is a life-saving interventional procedure to remove a blood clot from the brain of stroke patients. The pressure and blood flow dynamics during this procedure are crucial in determining the clinical outcomes. A mathematical model based on Hagen-Poiseuille law of fluid flow in a tube is adapted to simulate the pressure and fluid flow characteristics in an in vitro model of an occluded and unoccluded cerebrovascular network that mimics a poor (unilateral) and good (symmetrical) collateral flow within the Circle of Willis. The results show that in the absence of an occlusion, the pressure and pressure drop are higher in the symmetrical network compared to that in the unilateral network. This is due to the additional limb in the symmetrical network that must be supplied, which is absent in the unilateral network. In the presence of an occlusion, the flow reduces in the obstructed vessel, the collateral flow, overall pressure and pressure drop increases in both systems, but is higher for the symmetrical network. The results compare qualitatively with those observed in in vitro studies and with clinical observations. The theoretical framework lays the foundation for more advanced models for the pressure and blood flow dynamics towards clinical applicability.

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