Three-dimensional regional strain analysis in porcine myocardial infarction: a 3T magnetic resonance tagging study

Soleimanifard, Sahar; Abd‐Elmoniem, Khaled Z.; Sasano, Tetsuo; Agarwal, Harsh; Abraham, M. Roselle; Abraham, Theodore P.; Prince, Jerry L.

doi:10.1186/1532-429x-14-85

Cited by 17 publications

(10 citation statements)

References 37 publications

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“…First, our simulation shows that in the presence of a non-contractile infarct, the time-averaged elastic myofiber stretch is higher in the adjacent BZ region compared to the homeostatic set point value found in the same region when the LV was normal (Figure 7). Consistent with this result, abnormal stretching of the tissue and reduced negative (contracting) strain magnitude were observed in the BZ in animal models and patients during systole (Kramer et al 1993;Ashikaga et al 2005;Rutz et al 2008;Soleimanifard et al 2012). When averaged over a cardiac cycle, the BZ elastic myofiber stretch would, therefore, be higher than that found in the remote region.…”

Section: Effects Of MI On Local Deformationsupporting

confidence: 62%

An integrated electromechanical-growth heart model for simulating cardiac therapies

Lee

Sundnes

Genet

et al. 2015

Biomech Model Mechanobiol

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An emerging class of models has been developed in recent years to predict cardiac growth and remodeling (G&R). We recently developed a cardiac G&R constitutive model that predicts remodeling in response to elevated hemodynamics loading, and a subsequent reversal of the remodeling process when the loading is reduced. Here, we describe the integration of this G&R model to an existing strongly coupled electromechanical model of the heart. A separation of timescale between growth deformation and elastic deformation was invoked in this integrated electromechanical-growth heart model. To test our model, we applied the G&R scheme to simulate the effects of myocardial infarction in a realistic left ventricular (LV) geometry using the finite element method. We also simulate the effects of a novel therapy that is based on alteration of the infarct mechanical properties. We show that our proposed model is able to predict key features that are consistent with experiments. Specifically, we show that the presence of a non-contractile infarct leads to a dilation of the left ventricle that results in a rightward shift of the pressure volume loop. Our model also predicts that G&R is attenuated by a reduction in LV dilation when the infarct stiffness is increased.

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Section: Effects Of MI On Local Deformationsupporting

confidence: 62%

An integrated electromechanical-growth heart model for simulating cardiac therapies

Lee

Sundnes

Genet

et al. 2015

Biomech Model Mechanobiol

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“…Here, principal strains are defined along coordinate directions that correspond to zero shear. It is interesting to note that this study eliminated segments that were not completely transmural, thus anticipating and accounting for the possibility of mechanical heterogeneity in the radial direction (116). Top: layer-specific speckle-tracking echocardiography depicting peak strain in a rat MI model with varying degrees of infarction across the myocardial wall.…”

Section: Imagingmentioning

confidence: 99%

In vivo assessment of regional mechanics post-myocardial infarction: A focus on the road ahead

Romito

Shazly

Spinale

2017

Journal of Applied Physiology

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Cardiovascular disease, particularly the occurrence of myocardial infarction (MI), remains a leading cause of morbidity and mortality (Go et al., 127: e6-e245, 2013; Go et al. 129: e28-e292, 2014). There is growing recognition that a key factor for post-MI outcomes is adverse remodeling and changes in the regional structure, composition, and mechanical properties of the MI region itself. However, in vivo assessment of regional mechanics post-MI can be confounded by the species, temporal aspects of MI healing, as well as size, location, and extent of infarction across myocardial wall. Moreover, MI regional mechanics have been assessed over varying phases of the cardiac cycle, and thus, uniform conclusions regarding the material properties of the MI region can be difficult. This review assesses past studies that have performed in vivo measures of MI mechanics and attempts to provide coalescence on key points from these studies, as well as offer potential recommendations for unifying approaches in terms of regional post-MI mechanics. A uniform approach to biophysical measures of import will allow comparisons across studies, as well as provide a basis for potential therapeutic markers.

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“…The achievable accuracy and quantitative nature of CMR have led to its broad application in research involving swine. For example, CMR in swine has been critical in basic research of atherosclerosis [ 16 ], myocardial infarction [ 14 , 17 ], for safety testing of devices [ 18 ], interventions [ 19 , 20 ], and contrast agents [ 21 ]. Studies such as this one that analyze nonlinearities associated with higher field imaging that can lead to errors in quantitation are of interest.…”

Section: Discussionmentioning

confidence: 99%

Improvement in B1+ Homogeneity and Average Flip Angle Using Dual-Source Parallel RF Excitation for Cardiac MRI in Swine Hearts

Schär

Ding

Herzka³

2015

PLoS ONE

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Cardiac MRI may benefit from increased polarization at high magnetic field strength of 3 Tesla but is challenged by increased field inhomogeneity. Initial human studies have shown that the radiofrequency (RF) excitation field (B1 +) used for signal excitation in the heart is both inhomogeneous and significantly lower than desired, potentially leading to image artifacts and biased quantitative measures. Recently, multi-channel transmit systems have been introduced allowing localized patient specific RF shimming based on acquired calibration B1 + maps. Some prior human studies have shown lower than desired mean flip angles in the hearts of large patients even after RF shimming. Here, 100 cardiac B1 + map pairs before and after RF shimming were acquired in 55 swine. The mean flip angle and the coefficient of variation (CV) of the flip angle in the heart were determined before and after RF shimming. Mean flip angle, CV, and RF shim values (power ratio and phase difference between the two transmit channels) were tested for correlation with cross sectional body area and the Right-Left/Anterior-Posterior ratio. RF shimming significantly increased the mean flip angle in swine heart from 74.4±6.7% (mean ± standard deviation) to 94.7±4.8% of the desired flip angle and significantly reduced CV from 0.11±0.03 to 0.07±0.02 (p<<1e-10 for both). These results compare well with several previous human studies, except that the mean flip angle in the human heart only improved to 89% with RF shimming, possibly because the RF shimming routine does not consider safety constraints in very large patients. Additionally, mean flip angle decreased and CV increased with larger cross sectional body area, however, the RF shimming parameters did not correlate with cross sectional body area. RF shim power ratio correlated weakly with Right-Left/Anterior-Posterior ratio but phase difference did not, further substantiating the need for subject specific cardiac RF shimming.

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Three-dimensional regional strain analysis in porcine myocardial infarction: a 3T magnetic resonance tagging study

Cited by 17 publications

References 37 publications

An integrated electromechanical-growth heart model for simulating cardiac therapies

An integrated electromechanical-growth heart model for simulating cardiac therapies

In vivo assessment of regional mechanics post-myocardial infarction: A focus on the road ahead

Improvement in B1+ Homogeneity and Average Flip Angle Using Dual-Source Parallel RF Excitation for Cardiac MRI in Swine Hearts

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