The Contribution of Left Ventricular Muscle Bands to Left Ventricular Rotation: Assessment by a 2-Dimensional Speckle Tracking Method

Hui, Ling; Pemberton, James; Hickey, Edward; Li, Xiao Kui; Lysyansky, Peter; Ashraf, Muhammad; Niemann, Petra S; Sahn, David J.

doi:10.1016/j.echo.2006.10.012

Cited by 39 publications

(31 citation statements)

References 12 publications

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“…In this regard, we observed that subendocardial torsion was greater than subepicardial torsion in euthyroid hearts (Fig. 6), and this pattern of regional torsion has been reported in hearts of large mammals (29) and humans (45). LV torsion results from the forces of the endocardial and epicardial muscle layers, which are arranged in opposing helical orientations, and changes in regional torsion can significantly impact overall torsion.…”

Section: In Vivo LV Mechanics After Dobutamine Treatmentsupporting

confidence: 65%

Altered in vivo left ventricular torsion and principal strains in hypothyroid rats

Chen

Somji²,

Yu³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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Altered in vivo left ventricular torsion and principal strains in hypothyroid rats. Am J Physiol Heart Circ Physiol 299: H1577-H1587, 2010. First published August 20, 2010 doi:10.1152/ajpheart.00406.2010.-The twisting and untwisting motions of the left ventricle (LV) lead to efficient ejection of blood during systole and filling of the ventricle during diastole. Global LV mechanical performance is dependent on the contractile properties of cardiac myocytes; however, it is not known how changes in contractile protein expression affect the pattern and timing of LV rotation. At the myofilament level, contractile performance is largely dependent on the isoforms of myosin heavy chain (MHC) that are expressed. Therefore, in this study, we used MRI to examine the in vivo mechanical consequences of altered MHC isoform expression by comparing the contractile properties of hypothyroid rats, which expressed only the slow ␤-MHC isoform, and euthyroid rats, which predominantly expressed the fast ␣-MHC isoform. Unloaded shortening velocity (Vo) and apparent rate constants of force development (ktr) were measured in the skinned ventricular myocardium isolated from euthyroid and hypothyroid hearts. Increased expression of ␤-MHC reduced LV torsion and fiber strain and delayed the development of peak torsion and strain during systole. Depressed in vivo mechanical performance in hypothyroid rats was related to slowed cross-bridge performance, as indicated by significantly slower Vo and ktr, compared with euthyroid rats. Dobutamine infusion in hypothyroid hearts produced smaller increases in torsion and strain and aberrant transmural torsion patterns, suggesting that the myocardial response to ␤-adrenergic stress is compromised. Thus, increased expression of ␤-MHC alters the pattern and decreases the magnitude of LV rotation, contributing to reduced mechanical performance during systole, especially in conditions of increased workload. magnetic resonance imaging; myosin heavy chain; myocardial contractility; dobutamine; cardiac muscle contraction DURING THE EARLY PHASE of isovolumic contraction, the ventricular apex and base initially rotate in a counterclockwise direction when viewed from the apex to base (55), and later in systole, the base rotates in a clockwise direction, whereas the apex continues to rotate in a counterclockwise direction (36). Toward the end of systole and early diastole, the direction of torsion is reversed as the ventricle untwists (51, 56). The systolic twisting and diastolic untwisting of the left ventricle (LV) optimize the ejection of blood and the filling of the chamber during systole and diastole, respectively. The pattern of ventricular rotation during systole and diastole is facilitated by the architectural design of the LV, in which the subendocardial fibers are oriented in a right-handed helix and the epicardial fibers in an opposing left-handed helix (64), creating the torsion associated with the wringing and unwringing motions of the heart. The sequence of electromechanical activation occurs in ...

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Section: In Vivo LV Mechanics After Dobutamine Treatmentsupporting

confidence: 65%

Altered in vivo left ventricular torsion and principal strains in hypothyroid rats

Chen

Somji²,

Yu³

et al. 2010

American Journal of Physiology-Heart and Circulatory Physiology

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“…This technique is gaining popularity in publications [40,41] and retains a good correlation with MRI studies [39]. Of particular interest is a publication by Hui et al [42] which studied the contribution to ventricular rotation of the two bundles of myocardial fibers that form the interventricular septum. Because of its wide availabity in comparison with TMRI, speckle tracking echocardiography may become the technique of choice for the determination of AMT at patient's bedside.…”

Section: Discussionmentioning

confidence: 99%

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

Carreras

Garcia-Barnes

Gil

et al. 2011

Int J Cardiovasc Imaging

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Cardiac magnetic resonance imaging (Cardiac MRI) has become a gold standard diagnostic technique for the assessment of cardiac mechanics, allowing the non-invasive calculation of left ventricular long axis longitudinal shortening (LVLS) and absolute myocardial torsion (AMT) between basal and apical left ventricular slices, a movement directly related to the helicoidal anatomic disposition of the myocardial fibers. The aim of this study is to determine AMT and LVLS behaviour and normal values from a group of healthy subjects. A group of 21 healthy volunteers (15 males) (age: 23-55 y.o., mean: 30.7 ± 7.5) were prospectively included in an observational study by cardiac MRI. Left ventricular rotation (degrees) was calculated by custom-made software (Harmonic Phase Flow) in consecutive LV short axis planes tagged cine-MRI sequences. AMT was determined from the difference between basal and apical planes LV rotations. LVLS (%) was determined from the LV longitudinal and horizontal axis cine-MRI images. All the 21 cases studied were interpretable, although in three cases the value of the LV apical rotation could not be determined. The mean rotation of the basal and apical planes at end-systole were -3.71° ± 0.84° and 6.73° ± 1.69° (n:18) respectively, resulting in a LV mean AMT of 10.48° ± 1.63° (n:18). End-systolic mean LVLS was 19.07 ± 2.71%. Cardiac MRI allows for the calculation of AMT and LVLS, fundamental functional components of the ventricular twist mechanics conditioned, in turn, by the anatomical helical layout of the myocardial fibers. These values provide complementary information about systolic ventricular function in relation to the traditional parameters used in daily practice.

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“…The noisy velocities were analyzed by the new method, to produce the LS-STE velocities and the peak rotation and peak circumferential strain values. For the rotating phantoms: a narrow ROI was chosen, encompassing either the inner, middle, or outer layers, thus limiting the measurement to be the average value for a narrow ROI as described by Hui et al [21]. For the small rotating phantom it was possible to apply only two narrow ROIs, so the results of the EchoPAC were compared only to the inner and outer layers.…”

Section: 222mentioning

confidence: 99%

“…The wide ROI was analyzed by the LS-STE program to produce myocardial rotation and circumferential strain values at three myocardial layers. The two narrow ROIs were analyzed by the EchoPAC to produce myocardial rotation and circumferential strain values for the inner half and the outer half of the myocardium as was done by Hui et al [21]. The results of the LS-STE program (three layers) were compared to the results of the EchoPAC (two layers) by: (1) averaging the LS-STE results of the inner and middle layers and comparing it to the inner ROI, analyzed by the EchoPAC.…”

Section: Echocardiography Protocolmentioning

confidence: 99%

“…Validation of the accuracy of measuring the strain in three layers was done using data from different phantoms: (1) a simulation of tissue rotation and shrinkage/ expansion in software, (2) a shrinking/expanding mechanical phantom. Following validation by phantoms, the transmural distribution of LV rotation and circumferential strain were measured in standard short axis cross-sections of normal rats by the LS-STE program and by manually applying the STE commercial program to the inner and outer layers of the myocardium as described by Hui et al [21]. The two methods were compared as another validation of the LS-STE program.…”

Section: Introductionmentioning

confidence: 99%

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Layer-specific assessment of left ventricular function by utilizing wavelet de-noising: a validation study

Bachner-Hinenzon

Ertracht

Lysiansky

et al. 2010

Med Biol Eng Comput

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Regional myocardial function assessment is essential for diagnosis and evaluation of heart disease. The purpose of this study was to enhance the spatial resolution of a speckle tracking echocardiography approach and enable layer-specific analysis of the myocardium. Following validation with software-implemented and mechanical phantoms versus imposed values, short-axis cines were obtained from 50 rats. The cines were post-processed by a speckle tracking commercial program, and the myocardial velocities were processed by a three-dimensional wavelet de-noising program, instead of the built-in smoothing process of the commercial program. Software-implemented phantom measurements yielded rotation errors of 7.5%, 2.9%, and 3.4%, for inner, middle, and outer layers, respectively. Analysis of a shrinking/expanding mechanical phantom yielded strain errors of 3%, 5%, and 7% for the three layers. Bland-Altman analysis showed agreement between the commercial and enhanced programs. Thus, layer-specific analysis is feasible while using echocardiography even on small animals such as rats.

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The Contribution of Left Ventricular Muscle Bands to Left Ventricular Rotation: Assessment by a 2-Dimensional Speckle Tracking Method

Cited by 39 publications

References 12 publications

Altered in vivo left ventricular torsion and principal strains in hypothyroid rats

Altered in vivo left ventricular torsion and principal strains in hypothyroid rats

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

Layer-specific assessment of left ventricular function by utilizing wavelet de-noising: a validation study

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