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On the assessment of right ventricular function using cardiac magnetic resonance imaging and echocardiography
Örebro University, School of Medical Sciences.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Transthoracic echocardiography (TTE) and cardiac magnetic resonance (CMR) imaging are two commonly used imaging modalities for evaluating the size and function of the heart. There are advantages and disadvantages associated with both modalities when examining the right ventricle (RV).

The RV is positioned partly behind the sternum and lung, sometimes causing shadows in the TTE images. This along with the complex shape of the RV makes volume calculations challenging by 2D TTE. CMR is considered to be the reference method for volume calculations of the ventricles. The valve separating the RV from the right atrium is however often oblique compared to the valve separating the left ventricle from the left atrium. This complicates RV volume calculations using conventional CMR short-axis stack images. The aim of this thesis was to find ways to improve the RV stroke volume and ejection fraction calculations using TTE and CMR.

A method, transferring the position of the tricuspid plane from RV long-axis images to short-axis images, was developed to improve the separation of the right atrium from the RV when calculating RV stroke volumes by CMR. The method provided calculations of RV stroke volumes with good agreement to reference volumes. Further, the movements contributing to the RV stroke volume was studied aiming to find new ways of calculating RV stroke volumes and ejection fraction by TTE. A model for RV stroke volume and ejection fraction calculations was evaluated showing underestimation of stroke volumes by TTE compared to CMR, which probably depend on differences in distance measurements using the two modalities. The model provided, however, promising results for ejection fraction calculations which was validated in a study of 37 participants that covered a wide range of EF.

Place, publisher, year, edition, pages
Örebro: Örebro university , 2016. , 79 p.
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 152
Keyword [en]
right ventricle, stroke volume, ejection fraction, cardiac magnetic resonance, ehocardiography
National Category
Surgery
Research subject
Surgery
Identifiers
URN: urn:nbn:se:oru:diva-51662ISBN: 978-91-7529-158-1OAI: oai:DiVA.org:oru-51662DiVA: diva2:952592
Public defence
2016-11-18, Universitetssjukhuset, hörsal C3, Södra Grev Rosengatan, Örebro, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2016-08-15 Created: 2016-08-15 Last updated: 2016-10-26Bibliographically approved
List of papers
1. Calculation of right ventricular stroke volume in short-axis MR images using the equation of the tricuspid plane
Open this publication in new window or tab >>Calculation of right ventricular stroke volume in short-axis MR images using the equation of the tricuspid plane
2012 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 32, no 1, 5-11 p.Article in journal (Refereed) Published
Abstract [en]

Short-axis (SA) magnetic resonance (MR) images are commonly planned parallel to the left atrioventricular valve. This orientation leads to oblique slices of the right ventricle (RV) with subsequent difficulties in separating the RV from the right atrium in the SA images. The insertion points of the tricuspid valve (TV) in the myocardium can be clearly identified in the right ventricle long axis (RVLA) and four-chamber (4CH) views. The purpose of this study was to develop a method that transfers the position of the tricuspid plane, as seen in the RVLA and 4CH views, to the SA images to facilitate the separation of the RV from the atrium. This methodology, termed Dissociating the Right Atrium from the Ventricle Volume (DRAW), was applied in 20 patients for calculations of right ventricular stroke volume (RVSV). The RVSV using DRAW (RVSVDRAW) was compared to left ventricular stroke volumes (LVSV) obtained from flow measurements in the ascending aorta. The RVSV was also determined using the conventional method (RVSVCONV) where the stack of images from the SA views are summarized, and a visual decision is made of the most basal slice to be included in the RV. The mean difference between RVSVDRAW and LVSV was 0.1 +/- 12.7 ml, while the mean difference between RVSVCONV and LVSV was 0.33 +/- 14.3 ml. Both the intra- and interobserver variability were small using the DRAW methodology, 0.6 +/- 3.5 and 1.7 +/- 2.7 ml, respectively. In conclusion, the DRAW method can be used to facilitate the separation of the RV and the atrium.

Place, publisher, year, edition, pages
Malden, USA: Wiley-Blackwell, 2012
Keyword
Atrioventricular, cardiovascular magnetic resonance imaging, image analysis, right atrium, right ventricle, separating, tricuspid valve, ventricular function
National Category
Cardiac and Cardiovascular Systems
Research subject
Medicine; Cardiology
Identifiers
urn:nbn:se:oru:diva-21715 (URN)10.1111/j.1475-097X.2011.01047.x (DOI)000297928900002 ()22152073 (PubMedID)2-s2.0-83555164864 (ScopusID)
Available from: 2012-02-22 Created: 2012-02-20 Last updated: 2016-10-25Bibliographically approved
2. A study to determine the contribution to right ventricle stroke volume from pulmonary and tricuspid valve displacement volumes
Open this publication in new window or tab >>A study to determine the contribution to right ventricle stroke volume from pulmonary and tricuspid valve displacement volumes
2015 (English)In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, E-ISSN 1475-097X, Vol. 35, no 4, 283-290 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Describing the systolic function of the right ventricle (RV) is a difficult task due to the complex shape and orientation of the RV. The purpose of this study was to investigate the extent to which the volumes encompassed by the pulmonary and tricuspid valve displacements contribute to the total right ventricle stroke volume (RVSV).

METHODS: Twelve healthy volunteers were examined using cardiac magnetic resonance (CMR). Two series of time-resolved axially rotated MR images were acquired that encompassed the tricuspid valve and the pulmonary valve, respectively. The volume related to each valve movement, the tricuspid plane displacement (TPD) and the pulmonary plane displacement (PPD), was determined by delineation in diastole and systole. These volumes, RVSVTPD and RVSVPPD , were compared to the stroke volume to determine the contributions to the total stroke volume from the TPD and the PPD. The remaining volume of the total RVSV was referred to as RVSVOther . An initial in vitro study was carried out to validate the accuracy of volume measurements using axially rotated images.

RESULTS: In vitro measurements indicated that the method for volumetric measurements using axially rotated images was a very accurate one, with a mean difference of 0·04 ± 0·10 ml. The in vivo measurements of RVSVTPD , RVSVPPD and RVSVOther were 45 ± 10%, 13 ± 2% and 42 ± 11%, respectively.

CONCLUSIONS: Right ventricle stroke volume is determined by different individual volume changes as follows: RVSVTPD together with RVSVOther contributes to almost the entire RVSV in nearly equal proportions, while RVSVPPD contributes only a small amount and is approximately 30% of either RVSVTPD or RVSVOther.

Keyword
magnetic resonance imaging, pulmonary valve, right ventricle, stroke volume, tricuspid valve
National Category
Cardiac and Cardiovascular Systems Physiology
Research subject
Cardiology; Physiology
Identifiers
urn:nbn:se:oru:diva-38860 (URN)10.1111/cpf.12162 (DOI)000356312800006 ()24810859 (PubMedID)2-s2.0-84930746323 (ScopusID)
Note

Funding Agencies:

Örebro County Council

European Union - European Regional Development Fund

Available from: 2014-11-20 Created: 2014-11-20 Last updated: 2016-10-25Bibliographically approved
3. Determination of Right Ventricular Volume by Combining Echocardiographic Distance Measurements
Open this publication in new window or tab >>Determination of Right Ventricular Volume by Combining Echocardiographic Distance Measurements
Show others...
2016 (English)In: Echocardiography, ISSN 0742-2822, E-ISSN 1540-8175, Vol. 33, no 6, 844-853 p.Article in journal (Refereed) Published
Abstract [en]

Background: The position of the right ventricle (RV), often partly behind the sternum, implies difficulties to image the RV free wall using transthoracic echocardiography (TTE) and consequently limits the possibilities of stroke volume calculations. The aim of this study was to evaluate whether the volume of the right ventricle (RV) can be determined by combining TTE distance measurements that do not need the RV free wall to be fully visualized.

Methods: The RV volume was approximated by an ellipsoid composed of three distances. Distance measurements, modeled RV stroke volumes (RVSV), and RV ejection fraction (RVEF) were compared to reference values obtained from cardiac magnetic resonance (CMR) imaging for 12 healthy volunteers.

Results: Inter-modality comparisons showed that distance measurements were significantly underestimated in TTE compared to CMR. The modeled RV volumes using TTE distance measurements were underestimated compared to reference CMR volumes. There was, however, for TTE an agreement between modeled RVSV and left ventricular stroke volumes determined by biplane Simpson's rule. Similar agreement was shown between modeled RVSV based on CMR distance measurements and the CMR reference. Regarding RVEF, further studies including patients with a wider range of RVEF are needed to evaluate the method.

Conclusion: In conclusion, the ellipsoid model of the RV provides good estimates of RVSVs, but volumes based on distance measurements from different modalities cannot be used interchangeably.

Place, publisher, year, edition, pages
Hoboken, USA: Wiley-Blackwell Publishing Inc., 2016
Keyword
Right ventricle, right ventricular volume, ejection fraction, echoc ardiography, cardiac magnetic resonance imaging
National Category
Cardiac and Cardiovascular Systems
Research subject
Cardiology
Identifiers
urn:nbn:se:oru:diva-50370 (URN)10.1111/echo.13173 (DOI)000379944600005 ()26841195 (PubMedID)2-s2.0-84975297303 (ScopusID)
Note

Funding Agency:

Örebro County Council

Available from: 2016-05-23 Created: 2016-05-23 Last updated: 2016-10-25Bibliographically approved
4. Right ventricular ejection fraction measurements using twodimensional echocardiography
Open this publication in new window or tab >>Right ventricular ejection fraction measurements using twodimensional echocardiography
(English)Manuscript (preprint) (Other academic)
National Category
Surgery
Research subject
Surgery
Identifiers
urn:nbn:se:oru:diva-53271 (URN)
Available from: 2016-10-25 Created: 2016-10-25 Last updated: 2016-10-25Bibliographically approved

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