Reconstruction and Quantification of Diffusion Tensor Imaging-Derived Cardiac Fibre and Sheet Structure in Ventricular Regions used in Studies of Excitation Propagation

Benson, Alan P.; Gilbert, Stephen; Li, P.; Newton, S. M.; Holden, Arun V.

doi:10.1051/mmnp:2008083

Cited by 12 publications

(14 citation statements)

References 66 publications

(133 reference statements)

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“…This is because some studies calculated the orientation of the aggregates using the secondary eigenvector 17,21,37,48,54 while others used the tertiary eigenvector. 8,13,30,37,55,56,58,59 The majority of studies, furthermore, project the vector prior to angle quantification, 13,17,30,48,[54][55][56]58,59 while others do not. 8,21,37 Some methods use absolute values, while others calculate the angle relative to another perpendicular plane, resulting in a 90°offset.…”

Section: Discussionmentioning

confidence: 99%

“…This is achieved either by placing a line between the apex and the area of fibrous continuity between the leaflets of the aortic and mitral valves, 8,19,53 or by interpolating a straight line between the centres of the ventricular cavity as obtained in a series of short axis images. 18,21,30,54 The difference between the two approaches is minimal, but the latter is easiest to automate in a user-independent fashion. We, therefore, chose this approach.…”

Section: Establishing Reference Pointsmentioning

confidence: 99%

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Anatomically correct assessment of the orientation of the cardiomyocytes using diffusion tensor imaging

et al. 2019

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Diffusion tensor imaging has been used for assessing the orientation of cardiac myocytes for decades. Striking methodological differences exist between studies when quantifying these orientations. This limits the comparability between studies, and impedes collaboration and the drawing of appropriate physiological conclusions.We have sought to elucidate these differences, permitting us to propose a standardised "tool set" that might better establish consensus in future studies.We fixed hearts from seven 25 kg pigs in formalin, and scanned them using diffusion tensor imaging. Using various angle definitions as found in literature, we assessed the orientations of cardiomyocytes, comparing them in terms of helical and intrusion angles, along with the orientation of their aggregations. The difference between assessment of the helical angle with and without relation to the epicardial curvature was 25.2°(SD: 7.9) at the base, 5.8°(1.9) at the equatorial level, and 28.0°(7.0) at the apex, ANOVA P = 0.001. In comparable fashion, the intrusion angle differed by 25.9°( 12.9), 7.6°(0.98) and 17.5°(4.7), P = 0.01, and the angle of the aggregates (E3-angle) differed by 25.0°(13.5) at the base, 9.4°(1.7) at the equator, and 23.1°(6.2) apically, P = 0.003. When assessing 14 definitions used in literature to calculate the orientation of aggregates, only 4 rendered identical results. The findings show that any attempt to use projection of eigenvectors introduces considerable bias. The epicardial curvature of the ventricular cone needs to be taken into account when seeking to provide accurate quantification of the orientation of the aggregated cardiomyocytes, especially in the apical and basal regions. This means that projection of eigenvectors should be avoided prior to quantifying myocyte orientation, especially when assessing radial orientation. Based on our results, we suggest appropriate methods for valid assessment of myocyte orientation using diffusion tensor imaging.

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Section: Discussionmentioning

confidence: 99%

Section: Establishing Reference Pointsmentioning

confidence: 99%

Anatomically correct assessment of the orientation of the cardiomyocytes using diffusion tensor imaging

et al. 2019

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“…Analysis of DT-MRI data sets has been previously described (4). Fiber inclination (helix) angles were extracted from 2-mm-thick and 15°-wide sectors of the equatorial LV and RV free walls.…”

Section: Methodsmentioning

confidence: 99%

Cardiac arrhythmia mechanisms in rats with heart failure induced by pulmonary hypertension

Benoist

Stones

Drinkhill

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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Pulmonary hypertension provokes right heart failure and arrhythmias. Better understanding of the mechanisms underlying these arrhythmias is needed to facilitate new therapeutic approaches for the hypertensive, failing right ventricle (RV). The aim of our study was to identify the mechanisms generating arrhythmias in a model of RV failure induced by pulmonary hypertension. Rats were injected with monocrotaline to induce either RV hypertrophy or failure or with saline (control). ECGs were measured in conscious, unrestrained animals by telemetry. In isolated hearts, electrical activity was measured by optical mapping and myofiber orientation by diffusion tensor-MRI. Sarcoplasmic reticular Ca(2+) handling was studied in single myocytes. Compared with control animals, the T-wave of the ECG was prolonged and in three of seven heart failure animals, prominent T-wave alternans occurred. Discordant action potential (AP) alternans occurred in isolated failing hearts and Ca(2+) transient alternans in failing myocytes. In failing hearts, AP duration and dispersion were increased; conduction velocity and AP restitution were steeper. The latter was intrinsic to failing single myocytes. Failing hearts had greater fiber angle disarray; this correlated with AP duration. Failing myocytes had reduced sarco(endo)plasmic reticular Ca(2+)-ATPase activity, increased sarcoplasmic reticular Ca(2+)-release fraction, and increased Ca(2+) spark leak. In hypertrophied hearts and myocytes, dysfunctional adaptation had begun, but alternans did not develop. We conclude that increased electrical and structural heterogeneity and dysfunctional sarcoplasmic reticular Ca(2+) handling increased the probability of alternans, a proarrhythmic predictor of sudden cardiac death. These mechanisms are potential therapeutic targets for the correction of arrhythmias in hypertensive, failing RVs.

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“…The mean FA estimated from DT-MRI datasets of the entire ventricles ranges from 0.25 for the dog [47] to 0.35 for the goat [48], and the mean FA for the human ventricular tissue wedge shown in §3.3 is 0.29. The FA can also provide a measure of pathology, as a decrease in FA is a loss of the local anisotropic architecture, and the anisotropic architecture underlies the spatial pattern of excitation and propagation.…”

Section: Diffusion Tensor Magnetic Resonance Imagingmentioning

confidence: 99%

Construction and validation of anisotropic and orthotropic ventricular geometries for quantitative predictive cardiac electrophysiology

et al. 2010

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Reaction -diffusion computational models of cardiac electrophysiology require both dynamic excitation models that reconstruct the action potentials of myocytes as well as datasets of cardiac geometry and architecture that provide the electrical diffusion tensor D, which determines how excitation spreads through the tissue. We illustrate an experimental pipeline we have developed in our laboratories for constructing and validating such datasets. The tensor D changes with location in the myocardium, and is determined by tissue architecture. Diffusion tensor magnetic resonance imaging (DT-MRI) provides three eigenvectors e i and eigenvalues l i at each voxel throughout the tissue that can be used to reconstruct this architecture. The primary eigenvector e 1 is a histologically validated measure of myocyte orientation (responsible for anisotropic propagation). The secondary and tertiary eigenvectors (e 2 and e 3 ) specify the directions of any orthotropic structure if l 2 is significantly greater than l 3 -this orthotropy has been identified with sheets or cleavage planes. For simulations, the components of D are scaled in the fibre and cross-fibre directions for anisotropic simulations (or fibre, sheet and sheet normal directions for orthotropic tissues) so that simulated conduction velocities match values from optical imaging or plunge electrode experiments. The simulated pattern of propagation of action potentials in the models is partially validated by optical recordings of spatio-temporal activity on the surfaces of hearts. We also describe several techniques that enhance components of the pipeline, or that allow the pipeline to be applied to different areas of research: Q ball imaging provides evidence for multi-modal orientation distributions within a fraction of voxels, infarcts can be identified by changes in the anisotropic structure-irregularity in myocyte orientation and a decrease in fractional anisotropy, clinical imaging provides human ventricular geometry and can identify ischaemic and infarcted regions, and simulations in human geometries examine the roles of anisotropic and orthotropic architecture in the initiation of arrhythmias.

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Reconstruction and Quantification of Diffusion Tensor Imaging-Derived Cardiac Fibre and Sheet Structure in Ventricular Regions used in Studies of Excitation Propagation

Cited by 12 publications

References 66 publications

Anatomically correct assessment of the orientation of the cardiomyocytes using diffusion tensor imaging

Anatomically correct assessment of the orientation of the cardiomyocytes using diffusion tensor imaging

Cardiac arrhythmia mechanisms in rats with heart failure induced by pulmonary hypertension

Construction and validation of anisotropic and orthotropic ventricular geometries for quantitative predictive cardiac electrophysiology

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