218 research outputs found
Principles of cardiovascular magnetic resonance feature tracking and echocardiographic speckle tracking for informed clinical use
Tissue tracking technology of routinely acquired cardiovascular magnetic resonance (CMR) cine acquisitions has increased the apparent ease and availability of non-invasive assessments of myocardial deformation in clinical research and practice. Its widespread availability thanks to the fact that this technology can in principle be applied on images that are part of every CMR or echocardiographic protocol. However, the two modalities are based on very different methods of image acquisition and reconstruction, each with their respective strengths and limitations. The image tracking methods applied are not necessarily directly comparable between the modalities, or with those based on dedicated CMR acquisitions for strain measurement such as tagging or displacement encoding. Here we describe the principles underlying the image tracking methods for CMR and echocardiography, and the translation of the resulting tracking estimates into parameters suited to describe myocardial mechanics. Technical limitations are presented with the objective of suggesting potential solutions that may allow informed and appropriate use in clinical applications
A new integrated approach to cardiac mechanics: reference values for normal left ventricle
The association between left ventricular (LV) myocardial deformation and hemodynamic forces is still mostly unexplored. The normative values and the effects of demographic and technical factors on hemodynamic forces are not known. The authors studied the association between LV myocardial deformation and hemodynamic forces in a large cohort of healthy volunteers. One-hundred seventy-six consecutive subjects (age range, 16\u201382; 51% women), with no cardiovascular risk factors or any relevant diseases, were enrolled. All subjects underwent an echo-Doppler examination. Both 2D global myocardial and endocardial longitudinal strain (GLS), circumferential strain (GCS), and the hemodynamic forces were measured with new software that enabled to calculate all these values and parameters from the three apical views. Higher LV mass index and larger LV volumes were found in males compared to females (85 \ub1 17 vs 74 \ub1 15\ua0g/m2 and 127 \ub1 28 vs 85 \ub1 18\ua0ml, p < 0.0001 respectively) while no differences of the mean values of endocardial and myocardial GLS and of myocardial GCS were found (p = ns) and higher endocardial GCS in women ( 12\ua030.6 \ub1 4.2 vs 12\ua031.8 \ub1 3.7; p = 0.05). LV longitudinal force, LV systolic longitudinal force and LV impulse were higher in men (16.2 \ub1 5.3 vs 13.2 \ub1 3.6; 25.1 \ub1 7.9 vs 19.4 \ub1 5.6 and 20.4 \ub1 7 vs 16.6 \ub1 5.2, p < 0.0001, respectively). A weak but statistically significant decline with age (p < 0.0001) was also found for these force parameters. This new integrated approach could differentiate normality from pathology by providing average deformation values and hemodynamic forces parameters, differentiated by age and gender
Combined flow-based imaging assessment of optimal cardiac resynchronization therapy pacing vector: A case report
Background: There are still many pendent issues about the effective evaluation of cardiac resynchronization
therapy impact on functional mitral regurgitation. In order to reduce the intrinsic difficulties of quantification of
functional mitral regurgitation itself, an automatic quantification of real-time three-dimensional full-volume color
Doppler transthoracic echocardiography was proposed as a new, rapid, and accurate method for the assessment of
functional mitral regurgitation severity. Recent studies suggested that images of left ventricle flow by echo-particle
imaging velocimetry could be a useful marker of synchrony. Echo-particle imaging velocimetry has shown that
regional anomalies of synchrony/synergy of the left ventricle are related to the alteration, reduction, or suppression
of the physiological intracavitary pressure gradients.
Case summary: We describe a case in which the two technologies are used in combination during acute
echocardiographic optimization of left pacing vector in a 63-year-old man, Caucasian, who showed worsening heart
failure symptoms a few days after an implant, and the effect of the device\u2019s optimization at 6-month follow-up.
Discussion: The degree of realignment of hemodynamic forces, with quantitative analysis of the orientation of blood
flow momentum (\u3c6), can represent improvement of fluid dynamics synchrony of the left ventricle, and explain, with a
new deterministic parameter, the effects of cardiac resynchronization therapy on functional mitral regurgitation. Realtime three-dimensional color flow Doppler quantification is feasible and accurate for measurement of mitral inflow, left
ventricular outflow stroke volumes, and functional mitral regurgitation severity.
Conclusion: This clinical case offers an innovative and accurate approach for acute echocardiographic optimization of
left pacing vector. It shows clinical utility of combined three-dimensional full-volume color Doppler transthoracic
echocardiography/echo-particle imaging velocimetry assessment to increase response to cardiac resynchronization
therapy, in terms of reduction of functional mitral regurgitation, improving fluid dynamics synchrony of the left
ventricle
Richardson's pair diffusion and the stagnation point structure of turbulence
DNS and laboratory experiments show that the spatial distribution of
straining stagnation points in homogeneous isotropic 3D turbulence has a
fractal structure with dimension D_s = 2. In Kinematic Simulations the time
exponent gamma in Richardson's law and the fractal dimension D_s are related by
gamma = 6/D_s. The Richardson constant is found to be an increasing function of
the number of straining stagnation points in agreement with pair duffusion
occuring in bursts when pairs meet such points in the flow.Comment: 4 pages; Submitted to Phys. Rev. Let
Intraventricular flow patterns during right ventricular apical pacing
Objectives To assess differences in blood flow
momentum (BFM) and kinetic energy (KE) dissipation in
a model of cardiac dyssynchrony induced by electrical
right ventricular apical (RVA) stimulation compared with
spontaneous sinus rhythm.
Methods We cross-sectionally enrolled 12 consecutive
patients (mean age 74\ub18 years, 60% male, mean left
ventricular ejection fraction 58%\ub16 %), within 48 hours
from pacemaker (PMK) implantation. Inclusion criteria
were: age>18 years, no PMK-dependency, sinus rhythm
with a spontaneous narrow QRS at the ECG, preserved
ejection fraction (>50%) and a low percentage of PMKstimulation (<20%). All the participants underwent a
complete echocardiographic evaluation, including left
ventricular strain analysis and particle image velocimetry.
Results Compared with sinus rhythm, BFM shifted from
27\ub13.3 to 34\ub17.6\ub0 (p=0.016), while RVA-pacing was
characterised by a 35% of increment in KE dissipation,
during diastole (p=0.043) and 32% during systole
(p=0.016). In the same conditions, left ventricle global
longitudinal strain (LV GLS) significantly decreased from
17\ub13.3 to 11%\ub12.8% (p=0.004) during RVA-stimulation.
At the multivariable analysis, BFM and diastolic KE
dissipation were significantly associated with LV GLS
deterioration (Beta Coeff.=0.54, 95% CI 0.07 to 1.00,
p=0.034 and Beta Coeff.=0.29, 95% CI 0.02 to 0.57,
p=0.049, respectively).
Conclusions In RVA-stimulation, BFM impairment and
KE dissipation were found to be significantly associated
with LV GLS deterioration, when controlling for potential
confounders. Such changes may favour the onset of
cardiac remodelling and sustain heart failure
Quantum open systems and turbulence
We show that the problem of non conservation of energy found in the
spontaneous localization model developed by Ghirardi, Rimini and Weber is very
similar to the inconsistency between the stochastic models for turbulence and
the Navier-Stokes equation. This sort of analogy may be useful in the
development of both areas.Comment: to appear in Physical Review
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