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Three-dimensional flow in the human left atrium
Linköping University, Department of Medicine and Health Sciences, Clinical Physiology . Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medicine and Health Sciences, Clinical Physiology . Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
Linköping University, Department of Medicine and Health Sciences, Clinical Physiology . Linköping University, Faculty of Health Sciences.ORCID iD: 0000-0003-1395-8296
Linköping University, Department of Biomedical Engineering, Biomedical Modelling and Simulation . Linköping University, The Institute of Technology.ORCID iD: 0000-0001-5526-2399
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2001 (English)In: Heart, ISSN 1355-6037, Vol. 86, no 4, 448-455 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Abnormal flow patterns in the left atrium in atrial fibrillation or mitral stenosis are associated with an increased risk of thrombosis and systemic embolisation; the characteristics of normal atrial flow that avoid stasis have not been well defined.

OBJECTIVES: To present a three dimensional particle trace visualisation of normal left atrial flow in vivo, constructed from flow velocities in three dimensional space.

METHODS: Particle trace visualisation of time resolved three dimensional magnetic resonance imaging velocity measurements was used to provide a display of intracardiac flow without the limitations of angle sensitivity or restriction to imaging planes. Global flow patterns of the left atrium were studied in 11 healthy volunteers.

RESULTS: In all subjects vortical flow was observed in the atrium during systole and diastolic diastasis (mean (SD) duration of systolic vortex, 280 (77) ms; and of diastolic vortex, 256 (118) ms). The volume incorporated and recirculated within the vortices originated predominantly from the left pulmonary veins. Inflow from the right veins passed along the vortex periphery, constrained between the vortex and the atrial wall.

CONCLUSIONS: Global left atrial flow in the normal human heart comprises consistent patterns specific to the phase of the cardiac cycle. Separate paths of left and right pulmonary venous inflow and vortex formation may have beneficial effects in avoiding left atrial stasis in the normal subject in sinus rhythm.

Place, publisher, year, edition, pages
2001. Vol. 86, no 4, 448-455 p.
Keyword [en]
atrium, blood flow, magnetic resonance imaging, haemodynamics
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-14554DOI: 10.1136/heart.86.4.448OAI: oai:DiVA.org:liu-14554DiVA: diva2:23716
Available from: 2007-06-04 Created: 2007-06-04 Last updated: 2016-03-14
In thesis
1. Dynamiskt lärande: En ämnesdidaktisk avhandling om fysiologiska fenomen och läkarstudentens lärande
Open this publication in new window or tab >>Dynamiskt lärande: En ämnesdidaktisk avhandling om fysiologiska fenomen och läkarstudentens lärande
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

It is well known that the outcome of teaching and learning in higher education is often unsatisfactory. Earlier studies have shown that medical students often have a surface approach to their studies and that misconceptions of fundamental physiological phenomena are common. The aim of this thesis is to support educational practice in medicine, particularly in medical physiology. The thesis can be categorised as subject matter-specific education research, which means that questions about teaching and learning are closely linked to the subject studied. The researcher should be well acquainted with the subject in question. The subject area dealt with in this thesis is physiological phenomena related to cardiovascular pressure-flow relations.

The thesis consists of studies of 3-dimensional intra cardiac pressure-flow phenomena in the heart (studies 1 and 2) and studies of how students conceive of and develop an understanding of physiological phenomena related to blood pressure and blood pressure regulation (studies 3 and 4).

Flow in the left atrium as well as inflow-patterns to the left ventricle were studied. The 3-dimensional method elucidates vortical flow phenomena which were previously unknown. The findings could contribute to increasing physicians and technicians understanding of flow phenomena in the diagnosis and assessment of heart disease and to the further development of diagnostic methods. In the studies of learning and understanding of physiological phenomena, the findings point to new aspects of a deep approach to learning, which have to do with the students’ ability to change perspective and adopt a variety of learning strategies to a phenomenon (Moving) versus a tendency to hold on to one explanatory model (Holding). The study also investigates the students’ ability to identify and apply fundamental physiological principles as well as how they conceive of the importance of detailed knowledge for understanding of physiology. The findings point to differences in the students’ conceptions of physiological principles. A problemising approach, which includes not only causally described relations, indicates a more complex conception of physiological phenomena. The study shows aspects of understanding which are seldom assessed in examinations.

The findings indicate a connection between the students’ approaches to learning and the quality of their understanding of fundamental physiological principles. In the thesis, teaching interventions are proposed in order to stimulate dynamic learning and a learning environment where students are not afraid to challenge their conceptions in order to acquire a rich and nuanced picture of physiological phenomena.

Place, publisher, year, edition, pages
Institutionen för medicin och vård, 2007
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 976
Keyword
Lärande, Förståelse, Fysiologi
National Category
Physiology
Identifiers
urn:nbn:se:liu:diva-9026 (URN)91-85643-34-3 (ISBN)
Public defence
2007-01-18, Berzeliussalen, Campus US, Universitetssjukhuset, Lihköping, 13:00 (English)
Opponent
Supervisors
Available from: 2007-06-04 Created: 2007-06-04 Last updated: 2009-08-22
2. Multidimensional magnetic resonance imaging: new methods for analysis of cardiovascular dynamics
Open this publication in new window or tab >>Multidimensional magnetic resonance imaging: new methods for analysis of cardiovascular dynamics
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular flow and motion occur in three-dimensional (3D) space and vary dynamically over the cardiac cycle. The description of these complicated patterns using non-invasive imaging requires new tools for data acquisition, processing and visualization. In this thesis, a number of techniques are presented, all of which aim at improving the description of multidimensional cardiovascular flow and motion.

For the study of cardiac motion, a new M-mode method was developed that uses time-resolved image data to retrospectively calculate an M-mode image along an arbitrary line. This reduces the dimensionality of the acquired image data to one dimension plus time, which facilitates the analysis of the motion of cardiac structures. In order to describe flow patterns within the heart and great vessels, phase contrast magnetic resonance imaging (MRI) can be used to accurately measure velocities. Existing techniques for the acquisition of phase contrast data were extended in order to acquire time-resolved 3D image data that contain information about all three velocity components in each voxel. A number of possible approaches for reducing the scan time required were applied. Reducing the scan time in MRI often results in images with a poor signal-to-noise ratio (SNR). Image processing techniques were therefore investigated that utilize adaptive filtering in order to reduce the noise level, while still preserving the details of small structures. Once multidimensional image data are acquired, there is an immediate need to visualize the data in a comprehensible way. Particle trace visualization of velocity vector data was applied in order to study flow patterns in the human heart. Using these methods, completely new insights into the patterns of blood flow within the left atrium were achieved. This and future applications are made possible by the powerful combination of massive multidimensional data sets and tools developed specifically for the complicated conditions of cardiovascular flow.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2003. 74 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 807
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-29438 (URN)14784 (Local ID)91-7373-616-3 (ISBN)14784 (Archive number)14784 (OAI)
Public defence
2003-04-29, Föreläsningssal Conrad, Universitetssjukhuset, Linköping, 13:15 (Swedish)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-01-04
3. Cardiovascular fluid dynamics: methods for flow and pressure field analysis from magnetic resonance imaging
Open this publication in new window or tab >>Cardiovascular fluid dynamics: methods for flow and pressure field analysis from magnetic resonance imaging
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cardiovascular blood flow is highly complex and incompletely understood. Blood flow patterns are expected to influence the opening and closing of normal and prosthetic heart valves, the efficiency of cardiac filling and ejection, and the resistance to thrombus formation within the heart. Conventional diagnostic techniques are poorly suited to the study of the three-dimensional (3D) blood flow patterns in the heart chambers and large vessels. Noninvasive methods have also been inadequate in studying intracardiac pressure differences, which are the driving force of flow and are critical in the evaluation of many cardiovascular abnormalities.

This thesis focuses on the development of non-invasive methods for analysis of 3D cardiovascular blood flow. Simultaneous study of cardiovascular fluid dynamics allowed knowledge exchange across the two disciplines, facilitating the development process and broadening the applicability of the methods.

A time-resolved 3D phase-contrast Magnetic Resonance lrnaging (MRI) technique was used to acquire the velocity vector field in a 3D volume encompassing the entire heart or a large vessel. Cardiovascular blood flow patterns were visualized by use of particle traces, which revealed, for instance, vortical flow patterns in the left atrium.

By applying the Navier-Stokes equation along a user-defined line in the 3D velocity vector field, the relative pressure could be obtained as an excellent supplement to the flow pattern visualization. Using a delineation of the blood pool, the time-varying 3D relative pressure field in the human left ventricle was obtained from the velocity field by use of the pressure Poisson equation.

A delineation of the heart muscle, a task that is almost impossible to perform on 3D MRI either automatically or manually, was also achieved by usage of particle traces. This segmentation allows automatic calculation of the 3D relative pressure field, as well as calculation of well-established parameters such as ventricle volume and mass.

Simultaneous 3D assessment of cardiovascular pressure and flow phenomena throughout the cardiac cycle offers an opportunity to expand our understanding of the basic determinants of time-varying flow in healthy and sick hearts, with the potential for improving our methods for diagnosis, medical treatment and surgical correction of cardiovascular diseases.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2001. 48 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 690
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-28144 (URN)12957 (Local ID)91-7373-021-1 (ISBN)12957 (Archive number)12957 (OAI)
Public defence
2001-05-23, Elsa Brändströmssalen, Universiterssjukhuset, Linköping, 10:15 (Swedish)
Opponent
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2013-09-03

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Fyrenius, AnnaWigström, LarsEbbers, TinoKarlsson, MattsEngvall, JanBolger, Ann F.

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