In vitro assessment of flow patterns and turbulence intensity in prosthetic heart valves using generalized phase‐contrast MRI

Kvitting, John‐Peder Escobar; Dyverfeldt, Petter; Sigfridsson, Andreas; Franzén, Stefan; Wigström, Lars; Bolger, Ann F.; Ebbers, Tino

doi:10.1002/jmri.22163

Cited by 41 publications

(36 citation statements)

References 29 publications

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“…A three-directional PC-MRI experiment with asymmetric fourpoint motion-encoding permits estimation of the IVSD in three-directions. This approach to PC-MRI turbulence mapping has been validated against laser-Doppler and particle image velocimetry, as well as computational fluid dynamics (CFD) both in-vitro and in-vivo (4,24,26,58). PC-MRI turbulence mapping is used in paper V to assess the degree of TKE in the LV of DCM patients and healthy subjects.…”

Section: Turbulent Kinetic Energymentioning

confidence: 99%

Quantification of 4D Left Ventricular Blood Flow in Health and Disease

Eriksson¹

2013

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The main function of the heart is to pump blood throughout the cardiovascular system by generating pressure differences created through volume changes. Although the main purpose of the heart and vessels is to lead the flowing blood throughout the body, clinical assessments of cardiac function are usually based on morphology, approximating the flow features by viewing the motion of the myocardium and vessels. Measurement of three-directional, three-dimensional and time-resolved velocity (4D Flow) data is feasible using magnetic resonance (MR). The focus of this thesis is the development and application of methods that facilitate the analysis of larger groups of data in order to increase our understanding of intracardiac flow patterns and take the 4D flow technique closer to the clinical setting.In the first studies underlying this thesis, a pathline based method for analysis of intra ventricular blood flow patterns has been implemented and applied. A pathline is integrated from the velocity data and shows the path an imaginary massless particle would take through the data volume. This method separates the end-diastolic volume (EDV) into four functional components, based on the position for each individual pathline at end-diastole (ED) and end-systole (ES). This approach enables tracking of the full EDV over one cardiac cycle and facilitates calculation of parameters such as e.g. volumes and kinetic energy (KE). Besides blood flow, pressure plays an important role in the cardiac dynamics. In order to study this parameter in the left ventricle, the relative pressure field was computed using the pressure Poisson equation. A comprehensive presentation of the pressure data was obtained dividing the LV blood pool into 17 pie-shaped segments based on a modification of the standard seventeen segment model. Further insight into intracardiac blood flow dynamics was obtained by studying the turbulent kinetic energy (TKE) in the LV. The methods were applied to data from a group of healthy subjects and patients with dilated cardiomyopathy (DCM). DCM is a pathological state where the cardiac function is impaired and the left ventricle or both ventricles are dilated.The validation study of the flow analysis method showed that a reliable user friendly tool for intra ventricular blood flow analysis was obtained. The application of this tool also showed that roughly one third of the blood that enters the LV, directly leaves the LV again in the same heart beat. The distribution of the four LV EDV components was altered in the DCM group as compared to the healthy group; the component that enters and leaves the LV during one cardiac cycle (Direct Flow) was significantly larger in the healthy subjects. Furthermore, when the kinetic energy was normalized by the volume for each component, at time of ED, the Direct Flow had the highest values in the healthy subjects. In the DCM group, however, the Retained Inflow and Delayed Ejection Flow had higher values. The relative pressure field showed to be highly heterogeneous, in the hea...

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Section: Turbulent Kinetic Energymentioning

confidence: 99%

Quantification of 4D Left Ventricular Blood Flow in Health and Disease

Eriksson¹

2013

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“…Despite continuous further developments and improvements, all the techniques have limitations to access the instantaneous flow field and therefore the turbulent fluctuations and shear stresses. Recently, the 4D velocity magnetic resonance imaging has been applied in many studies to access the velocity field in vessels (Bogren et al 2004;Dyverfeldt et al 2006Dyverfeldt et al , 2008Frydrychowicz et al 2007;Kilner et al 1993;Kozerke et al 2001;Kvitting et al 2010;Markl et al 2005) and Morbiducci et al (2009). One of the aims of this study is to measure both the instantaneous and the phase-averaged flow field in a realistic aorta.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of aortic flow in the ascending aorta via Particle Tracking Velocimetry

et al. 2012

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A three-dimensional, pulsatile flow in a realistic phantom of a human ascending aorta with compliant walls is investigated in vitro. Three-Dimensional Particle Tracking Velocimetry (3D-PTV), an image-based, nonintrusive measuring method is used to analyze the aortic flow. The flow velocities and the turbulent fluctuations are determined. The velocity profile at the inlet of the ascending aorta is relatively flat with a skewed profile toward the inner aortic wall in the early systole. In the diastolic phase, a bidirectional flow is observed with a pronounced retrograde flow developing along the inner aortic wall, whereas the antegrade flow migrates toward the outer wall of the aorta. The spatial and temporal evolution of the vorticity field shows that the vortices begin developing along the inner wall during the deceleration phase and attenuate in the diastolic phase. The change in the cross-sectional area is more distinct distal to the inlet cross section. The mean kinetic energy is maximal in the peak systole, whereas the turbulent kinetic energy increases in the deceleration phase and reaches a maximum in the beginning of the diastolic phase. Finally, in a Lagrangian analysis, the temporal evolution of particle dispersion was studied. It shows that the dispersion is higher in the deceleration phase and in the beginning of the diastole, whereas in systole, it is smaller but non-negligible.

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“…Cheng et al [22], for example, computed a maximum wall shear stress exceeding 160,000 dynes/cm 2 at the tip of a closed bileaflet valve. There has been more recent work using particle image velocimetry and numerical methods to understand the fluid dynamics associated with bileaflet valves focusing on overall hemodynamics and specifically investigating the hinge flow region [23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Near Valve Flows and Potential Blood Damage During Closure of a Bileaflet Mechanical Heart Valve

Herbertson

Deutsch

Manning

2011

Journal of Biomechanical Engineering

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Blood damage and thrombosis are major complications that are commonly seen in patients with implanted mechanical heart valves. For this in vitro study, we isolated the closing phase of a bileaflet mechanical heart valve to study near valve fluid velocities and stresses. By manipulating the valve housing, we gained optical access to a previously inaccessible region of the flow. Laser Doppler velocimetry and particle image velocimetry were used to characterize the flow regime and help to identify the key design characteristics responsible for high shear and rotational flow. Impact of the closing mechanical leaflet with its rigid housing produced the highest fluid stresses observed during the cardiac cycle. Mean velocities as high as 2.4 m/s were observed at the initial valve impact. The velocities measured at the leaflet tip resulted in sustained shear rates in the range of 1500-3500 s À1 , with peak values on the order of 11,000-23,000 s À1. Using velocity maps, we identified regurgitation zones near the valve tip and through the central orifice of the valve. Entrained flow from the transvalvular jets and flow shed off the leaflet tip during closure combined to generate a dominant vortex posterior to both leaflets after each valve closing cycle. The strength of the peripheral vortex peaked within 2 ms of the initial impact of the leaflet with the housing and rapidly dissipated thereafter, whereas the vortex near the central orifice continued to grow during the rebound phase of the valve. Rebound of the leaflets played a secondary role in sustaining closure-induced vortices.

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In vitro assessment of flow patterns and turbulence intensity in prosthetic heart valves using generalized phase‐contrast MRI

Cited by 41 publications

References 29 publications

Quantification of 4D Left Ventricular Blood Flow in Health and Disease

Quantification of 4D Left Ventricular Blood Flow in Health and Disease

Experimental study of aortic flow in the ascending aorta via Particle Tracking Velocimetry

Near Valve Flows and Potential Blood Damage During Closure of a Bileaflet Mechanical Heart Valve

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