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The rotation axis of the left ventricle - A new concept derived from ultrasound data in healthy individuals
KTH, School of Technology and Health (STH), Medical Engineering. (Skolan för teknik och hälsa)ORCID iD: 0000-0002-5795-9867
(English)Manuscript (preprint) (Other (popular science, discussion, etc.))
Abstract [en]

Different modalities have been used to describe the circumferential motion of the left ventricle (LV) and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes of rotation have been reported, whereas the rotation pattern of the LV has not been fully described. However, data from a previous study on regional rotation have indicated that the axis around which the LV rotates, is not congruent to the longitudinal axis of the LV. The aim of the present study was to develop an ultrasound-based method to calculate the rotation axis of the LV in a three-dimensional aspect throughout the cardiac cycle and to apply it in a group of healthy individuals. An algorithm for calculation of rotation axes at the basal, mid-, apical and transitional levels of the LV was developed. By constructing a simplified model of the LV, based on rotation amplitudes measured at the basal, mid- and apical levels, rotation planes with similar values of rotation could be calculated at each level. The transition plane was defined as where the rotation values shifted from positive to negative. An overview of the rotation pattern was achieved by displaying data on deflection (angle between the rotation axis and the longitudinal axis of the LV) and direction (defined as the angle in a short-axis view of the LV with zero degrees at the lateral wall and increasing angles counterclockwise) of the rotation axes throughout the cardiac cycle. The deflection differed significantly from zero in all tested time points, i.e. the rotation axis was not congruent to the longitudinal axis of the LV. Rayleigh’s test for uniformity demonstrated a significant mean direction for each of the axes for the majority of the tested time points. Thus, the axis of rotation at different levels of the LV displayed a physiological pattern, where also stability of rotation could be assessed. Furthermore, the angle and level of the transition plane could be described over time. This new way of assessing rotational function provides further insight into the complexity of LV mechanics. The method has acceptable reproducibility but the potential clinical use of this method needs to be validated in further studies.

National Category
Medical Laboratory and Measurements Technologies
Identifiers
URN: urn:nbn:se:kth:diva-11749OAI: oai:DiVA.org:kth-11749DiVA: diva2:280825
Note
QC 2010727Available from: 2009-12-11 Created: 2009-12-11 Last updated: 2010-10-04Bibliographically approved
In thesis
1. Quantification and Visualization of Cardiovascular Function using Ultrasound
Open this publication in new window or tab >>Quantification and Visualization of Cardiovascular Function using Ultrasound
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

There is a large need for accurate methods detecting cardiovascular diseases, since they are one of the leading causes of mortality in the world, accounting for 29.3% of all deaths. Due to the complexity of the cardiovascular system, it is very challenging to develop methods for quantification of its function in order to diagnose, prevent and treat cardiovascular diseases. Ultrasound is a technique allowing for inexpensive, noninvasive imaging, but requires an experienced echocardiographer. Nowadays, methods like Tissue Doppler imaging (TDI) and Speckle tracking imaging (STI), measuring motion and deformation in the myocardium and the vessel walls, are getting more common in routine clinical practice, but without a proper visualization of the data provided by these methods, they are time-consuming and difficult to interpret. Thus, the general aim of this thesis was to develop novel ultrasound-based methods for accurate quantification and easily interpretable visualization of cardiovascular function.

Five methods based on TDI and STI were developed in the present studies. The first study comprised development of a method for generation of bull’s-eye plots providing a color-coded two-dimensional visualization of myocardial longitudinal velocities. The second study proposed the state diagram of the heart as a new circular visualization tool for cardiac mechanics, including segmental color-coding of cardiac time intervals. The third study included development of a method describing the rotation pattern of the left ventricle by calculating rotation axes at different levels of the left ventricle throughout the cardiac cycle. In the fourth study, deformation data from the artery wall were tested as input to wave intensity analysis providing information of the ventricular – arterial interaction. The fifth study included an in-silico feasibility study to test the assessment of both radial and longitudinal strain in a kinematic model of the carotid artery.

The studies showed promising results indicating that the methods have potential for the detection of different cardiovascular diseases and are feasible for use in the clinical setting. However, further development of the methods and both quantitative comparison of user dependency, accuracy and ease of use with other established methods evaluating cardiovascular function, as well as additional testing of the clinical potential in larger study populations, are needed.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. x, 72 p.
Series
Trita-STH : report, ISSN 1653-3836 ; 2009:6
Keyword
Ultrasound, Tissue Doppler imaging, Speckle tracking imaging, cardiovascular function, visualization, quantification
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:kth:diva-11762 (URN)978-91-7415-524-2 (ISBN)
Public defence
2010-01-22, 3-221, Alfred Nobels Alle 10, Huddinge, 08:30 (Swedish)
Opponent
Supervisors
Note
QC 20100727Available from: 2009-12-14 Created: 2009-12-11 Last updated: 2010-10-04Bibliographically approved

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