Left ventricular torsion and longitudinal shortening: two fundamental components of myocardial mechanics assessed by tagged cine-MRI in normal subjects

Carreras, Francesc; Garcia-Barnes, Jaume; Gil, Débora; Pujadas, Sandra; Li, Chi-Hion; Suarez-Arias, Ramon; Leta, Rubén; Alomar, Xavier; Ballester, Manel; Pons-Lladó, Ġuillem

doi:10.1007/s10554-011-9813-6

Cited by 46 publications

(44 citation statements)

References 38 publications

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“…Rotational motion and twist of the left ventricle has not been specifically considered. Changes in torsion correlate closely with longitudinal strain [54] and stress-corrected strain and torsion are similarly related to ejection fraction [7]. Modelling torsion and twist was deemed unnecessary as this would not impact on the volume determinations or other outcomes.…”

Section: Limitations and Future Studiesmentioning

confidence: 99%

Left ventricular ejection fraction is determined by both global myocardial strain and wall thickness

MacIver

Adeniran

Zhang

2015

IJC Heart & Vasculature

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ObjectivesThe purpose of this study was to determine the mathematical relationship between left ventricular ejection fraction and global myocardial strain. A reduction in myocardial strain would be expected to cause a fall in ejection fraction. However, there is abundant evidence that abnormalities of myocardial strain can occur with a normal ejection fraction. Explanations such as a compensatory increase in radial or circumferential strain are not supported by clinical studies. We set out to determine the biomechanical relationship between ejection fraction, wall thickness and global myocardial strain.MethodsThe study used an established abstract model of left ventricular contraction to examine the effect of global myocardial strain and wall thickness on ejection fraction. Equations for the relationship between ejection fraction, wall thickness and myocardial strain were obtained using curve fitting methods.ResultsThe mathematical relationship between ejection fraction, ventricular wall thickness and myocardial strain was derived as follows: φ = e(0.14Ln(ε) + 0.06)ω + (0.9Ln(ε) + 1.2), where φ is ejection fraction (%), ω is wall thickness (cm) and ε is myocardial strain (−%).ConclusionThe findings of this study explain the coexistence of reduced global myocardial strain and normal ejection fraction seen in clinical observational studies. Our understanding of the pathophysiological processes in heart failure and associated conditions is substantially enhanced. These results provide a much better insight into the biophysical inter-relationship between myocardial strain and ejection fraction. This improved understanding provides an essential foundation for the design and interpretation of future clinical mechanistic and prognostic studies.

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Section: Limitations and Future Studiesmentioning

confidence: 99%

Left ventricular ejection fraction is determined by both global myocardial strain and wall thickness

MacIver

Adeniran

Zhang

2015

IJC Heart & Vasculature

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“…Each motor rotated 30 degrees at a speed of 112 degrees per second. These rotation parameters were chosen to mimic the rotation rate and degree in the normal human heart (Carreras et al 2011). RF frames were acquired in three distinct locations: through the center of the phantom, and 5 cm towards the left or right edge of the phantom, as shown in figure 1.…”

Section: Methodsmentioning

confidence: 99%

Assessment of myocardial elastography performance in phantoms under combined physiologic motion configurations with preliminaryin vivofeasibility

Okrasinski¹,

Konofagou²

2012

Phys. Med. Biol.

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Myocardial Elastography (ME) is a non-invasive, ultrasound-based strain imaging technique, which can detect and localize abnormalities in myocardial function. By acquiring radio-frequency (RF) frames at high frame rates, the deformation of the myocardium can be estimated, and used to identify regions of abnormal deformation indicative of cardiovascular disease. In this study, the primary objective is to evaluate the effect of torsion on the performance of ME, while the secondary objective is to image inclusions during different motion schemes. Finally, the phantom findings are validated with an in vivo human case. Phantoms of homogeneous stiffness, or containing harder inclusions, were fixed to a pump and motors, and imaged. Incremental displacements were estimated from the RF signals, and accumulated over a motion cycle, and rotation angle, radial strain, and circumferential strain were estimated. Phantoms were subjected to 4 motion schemes: rotation, torsion, deformation, and a combination of torsion and deformation. Sonomicrometry was used as a gold standard during deformation and combined motion schemes. In the rotation scheme, the input and estimated rotation angle agree in both the homogeneous and inclusion phantoms. In the torsion scheme, the estimated rotation angle was found to be highest closest to the source of torsion and lowest farthest from the source of torsion. In the deformation scheme, if an inclusion was not present, the estimated strain patterns accurately depicted homogeneity, while if an inclusion was present, abnormalities were observed which enabled detection of the inclusion. In addition, no significant rotation was detected. In the combined scheme, if an inclusion was not present, the estimated strain patterns accurately depicted homogeneity, while, if an inclusion was present, abnormalities were observed which enabled detection of the inclusion. Also, torsion was separated from the combined scheme and was found to be similar to the pure torsion findings. This study shows ME to be capable of accurately depicting and distinguishing between different types of motion schemes, and to be sensitive to stiffness changes in localized regions of tissue-mimicking phantoms under physiologic cardiac motion configurations, while strains estimated in the combined motion scheme were noisier than in individual motion schemes. Finally, ME was shown to distinguish between deformation and rotation in a normal human subject.

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“…81 Torsional motion was modelled by myocyte contraction patterns creating a realistic counter-clockwise apical rotation with respect to the base. [82][83][84] The finite element problem was solved by means of the commercial code Abaqus (Abaqus 6.14, SIMULIA, Dessault Systemes).…”

Section: Finite Element Modellingmentioning

confidence: 99%

Genomic analysis reveals a functional role for myocardial trabeculae in adults

Meyer

Dawes

Serrani

et al. 2019

Preprint

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Since being first described by Leonardo da Vinci in 1513 it has remained an enigma why the endocardial surfaces of the adult heart retain a complex network of muscular trabeculae -with their persistence thought to be a vestige of embryonic development. For causative physiological inference we harness population genomics, image-based intermediate phenotyping and in silico modelling to determine the effect of this complex cardiovascular trait on function. Using deep learning-based image analysis we identified genetic associations with trabecular complexity in 18,097 UK Biobank participants which were replicated in an independently measured cohort of 1,129 healthy adults. Genes in these associated regions are enriched for expression in the fetal heart or vasculature and implicate loci associated with haemodynamic phenotypes and developmental pathways. A causal relationship between increasing trabecular complexity and both ventricular performance and electrical activity are supported by complementary biomechanical simulations and Mendelian randomisation studies. These findings show that myocardial trabeculae are a previously-unrecognised determinant of cardiovascular physiology in adult humans.1 complexity and use Mendelian randomisation to provide a causal inference framework. We then use a finite-element model of the heart with physiologically-realistic loading conditions to determine the haemodynamic effect of varying trabecular complexity whilst keeping other parameters constant. This multi-disciplinary approach to physiological inference suggests a causal relationship between trabecular complexity and ventricular efficiency implicating loci associated with haemodynamic phenotypes and developmental pathways. Data overviewUK Biobank is a prospective cohort study collecting deep genetic and phenotypic data on approximately 500,000 individuals from across the United Kingdom, aged between 40 and 69 at recruitment, providing opportunities for the discovery of the genetic basis of complex traits. 16 Of these, 100,000 participants are being recalled for enhanced phenotyping which includes cardiac magnetic resonance (CMR) imaging. 17 Non-invasive data on a range of haemodynamic parameters are also collected at the time of imaging. Following automated image-quality control 18 and exclusion of subjects with missing covariates, 18,097 unrelated participants that formed a well mixed population of European ethnicity (Figure 7 in the Supplement) were used for discovery (Table 1 and Figure 1D). An independent cohort comprising 1,129 healthy adults recruited in London, UK with both genotypes and CMR imaging was used for validation. 19 Fractal dimension analysis of left ventricular trabeculationWe used a fully convolutional network for automated left ventricular segmentation and volumetry. 20 The complexity of myocardial trabeculae ( Figure 1A) was quantified by the scale-invariant ratio of fractal dimension (FD, Figure 1C). 21 To account for variations in cardiac size and for consistent anatomical comparisons within and between ...

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Left ventricular torsion and longitudinal shortening: two fundamental components of myocardial mechanics assessed by tagged cine-MRI in normal subjects

Cited by 46 publications

References 38 publications

Left ventricular ejection fraction is determined by both global myocardial strain and wall thickness

Left ventricular ejection fraction is determined by both global myocardial strain and wall thickness

Assessment of myocardial elastography performance in phantoms under combined physiologic motion configurations with preliminaryin vivofeasibility

Genomic analysis reveals a functional role for myocardial trabeculae in adults

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