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Spatial heterogeneity of 4D relative pressure fields in the human left ventricle
Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.ORCID iD: 0000-0003-2198-9690
Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Medical and Health Sciences, Physiology. Linköping University, Faculty of Health Sciences. Linköping University, Department of Science and Technology, Media and Information Technology.ORCID iD: 0000-0003-1395-8296
2013 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Blood flow throughout the cardiovascular system is driven by pressure differences generated by the contraction and relaxation of the heart, where blood accelerates from high to low pressure areas. Absolute intracardiac pressure cannot be measured noninvasively, but relative pressure can be calculated. The aim of this study was to assess the spatial heterogeneity of the 4D relative pressure fields in the human left ventricle (LV).

Twelve healthy subjects underwent MRI examination where 4D flow as well as morphological data were acquired. The morphological data were segmented, and the segmentation used as boundary condition when computing relative pressure fields from the pressure Poisson equation using a multi grid solver. The LV lumen was divided according to a seventeen segment model in order to assess spatial heterogeneity and present the extensive amount of data in a comprehensive manner.

The basal anteroseptal segment shows a significantly lower median pressure than the opposite basal inferolateral segment during both early and late diastolic filling (p<0.0005 and p=0.0024, respectively). Along the long axis, the relative pressure in the apical segments are significantly higher relative to the basal segments (p<0.0005) along both the anteroseptal and inferolateral sides at and after the peaks of E-wave and A-wave.

During diastole the main pressure differences in the LV occur along the basal-apical axis. However, pressure differences can also be found in the short-axis direction, and may also reflect important aspects of atrioventricular coupling.

Place, publisher, year, edition, pages
2013. Vol. 14
Keyword [en]
Relative pressure, Magnetic resonance, 4D flow, physiology, cardiac function
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-99956OAI: oai:DiVA.org:liu-99956DiVA: diva2:659079
Available from: 2013-10-24 Created: 2013-10-24 Last updated: 2014-04-23Bibliographically approved
In thesis
1. Quantification of 4D Left Ventricular Blood Flow in Health and Disease
Open this publication in new window or tab >>Quantification of 4D Left Ventricular Blood Flow in Health and Disease
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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 healthy heart. During diastole the predominate pressure differences in the LV occur along the long axis from base to apex. The distribution and variability of 3D pressure fields differ between early and late diastolic filling phases, but common to both phases is a relatively lower pressure in the outflow segment. In the normal LV, TKE values are low. The highest TKE values can be seen during early diastole and are regionally distributed near the basal LV regions. In contrast, in a heterogeneous group of DCM patients, total diastolic and late diastolic TKE values are higher than in normals, and increase with the LV volume.

In conclusion, in this thesis, methods for analysis of multidirectional intra cardiac velocity data have been obtained. These methods allow assessment of data quality, intra cardiac blood flow patterns, relative pressure fields, and TKE. Using these methods, new insights have been obtained in intra cardiac blood flow dynamics in health and disease. The work underlying this thesis facilitates assessment of data from a larger population of healthy subjects and patients, thus bringing the 4D Flow MRI technique closer to the clinical setting.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 63 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1374
Keyword
MRI, relative pressure, 4D flow, quantification, turbulent kinetic energy, dilated cardiomyopathy, magnetic resonance imaging, physiology, cardiac function, diastolic dysfunction
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-98786 (URN)10.3384/diss.diva-99958 (DOI)978-91-7519-542-1 (ISBN)
Public defence
2013-11-22, Berzeliussalen, Campus US, Linköpings universitet, Linköping, 09:00 (English)
Opponent
Supervisors
Available from: 2013-10-14 Created: 2013-10-14 Last updated: 2014-04-23Bibliographically approved

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Eriksson, JonatanBolger, Ann F.Carlhäll, Carl-JohanEbbers, Tino

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