Alterations in Transmural Myocardial Strain

Carlhäll, Carl‐Johan; Nguyen, Tom C.; Itoh, Akinobu; Ennis, Daniel B.; Bothe, Wolfgang; Liang, David; Ingels, Neil B.; Miller, D. Craig

doi:10.1161/circulationaha.107.753525

Cited by 17 publications

(14 citation statements)

References 38 publications

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“…These results build upon data demonstrating regional contractile dysfunction that has been observed in mitral valve prolapse or within the setting of congestive heart failure and dilated cardiomyopathy 15, 23 . This heterogeneous injury pattern is furthermore consistent with experimental animal data that suggests that the earliest contractile injury in MR is not only likely to be regional but may also vary across LV wall thickness 24 .…”

Section: Discussionsupporting

confidence: 87%

Early left ventricular regional contractile impairment in chronic mitral regurgitation occurs in a consistent, heterogeneous pattern

Maniar¹,

Brady²,

Lee³

et al. 2014

The Journal of Thoracic and Cardiovascular Surgery

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Objectives Clinical guidelines for asymptomatic patients with chronic MR utilize ejection fraction (EF) to trigger surgical referral. We hypothesize that 1) EF is not sensitive enough to detect the earliest contractile injury in chronic MR and 2) that the injury associated with chronic MR is not global but heterogeneous, occurring regionally and predictably, prior to the onset of global left ventricular (LV) dysfunction. Methods Fifteen patients with chronic MR and normal LV EF by echocardiography underwent cardiac MRI with tissue tagging. Point-specific comparisons (at 15,300 LV grid points) of multiple strain parameters to a normal human strain database allowed normalization of patient-specific regional contractile function. Data were mapped over patient-specific 3D geometry, then averaged across six LV regions. Results Global LV longitudinal and circumferential myocardial strains were normal for all 15 MR patients when compared to normal controls (p>0.05). Despite preserved global function, the anteroseptum and posteroseptum demonstrated significantly worse contractile function when compared to other regions of the LV (p=0.003 and p=0.035, respectively). Hyper-contractile regions (lateral walls) appeared to compensate (p=0.002) for the reduced septal contractile function thereby masking injury detection by global indices. Conclusion The earliest contractile injury seen in MR patients is heterogeneous, and consistently distributed along the LV septum. Compensatory responses include hypercontractility of other regions. These data suggest that rather than relying upon global LV contractile metrics, which do not detect early injury, patients may be better served by undergoing directed surveillance of “sentinel” LV regions (LV septum) with high-resolution metrics of regional contractile function.

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Section: Discussionsupporting

confidence: 87%

Early left ventricular regional contractile impairment in chronic mitral regurgitation occurs in a consistent, heterogeneous pattern

Maniar¹,

Brady²,

Lee³

et al. 2014

The Journal of Thoracic and Cardiovascular Surgery

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“…27 Perhaps because of their less load-dependent nature, these measures have also proven informative in the setting of valvular heart disease in which alterations in loading conditions make EF a less reliable measure of contractile function, including severe aortic stenosis, 28 aortic regurgitation, 29 and mitral regurgitation. 30 In the case of coronary disease, global strain values obtained early after an acute myocardial infarction may effectively predict subsequent remodeling and functional recovery. [31][32][33] …”

Section: Deformation Imaging As a Measure Of LV Function Detection Ofmentioning

confidence: 99%

Myocardial Deformation Imaging

2012

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M yocardial deformation imaging is a novel echocardiographic method for assessment of global and regional myocardial function. As this technology has evolved, it has been applied to an increasing number of research questions, and the number of publications incorporating deformation imaging has grown in parallel.Although not yet sufficiently vetted for routine clinical use, these methods offer the long-term potential for more complete, accurate, and reproducible assessment of myocardial function. What Is Myocardial Deformation Imaging?Evaluation of contractile function with echocardiography has traditionally been limited to volume-based assessment of ejection fraction (EF) and assessment of regional wall motion or visual estimation of regional thickening. These methods have suffered from lack of reproducibility and standardization and are generally considered to be extremely sensitive to loading conditions. These limitations have led to an interest in techniques that provide more objective and reproducible measures of contractile function.During systole, the ventricular myocardium simultaneously shortens in the longitudinal and circumferential planes and thickens in the radial plane, with reciprocal changes in diastole ( Figure). Deformation imaging, in the broadest sense, allows for more direct assessment of myocardial muscle shortening and lengthening throughout the cardiac cycle by assessing regional myocardial strain and strain rate. Strain is defined as the change in length of a segment of myocardium relative to its resting length and is expressed as a percentage; strain rate is the rate of this deformation. Longitudinal and circumferential shortening results in negative strain values, whereas radial thickening results in a positive strain value. Previously, assessment of myocardial strain could be performed with the use of sonomicrometry crystals, which can only be performed experimentally 1 or with magnetic resonance imaging-based myocardial tagging, 2,3 which is limited by relatively low temporal resolution and the limited availability and expense of cardiac magnetic resonance imaging. Extension of these techniques to echocardiography has allowed for substantially greater utility in a broader range of patients.Myocardial deformation imaging with echocardiography can be performed with the use of either tissue Doppler-based or 2-dimensional speckle tracking-based methods. Doppler methods, developed initially, utilize the velocity gradient present along the length of the left ventricle (LV) to calculate strain rate, which is then integrated to derive strain. This technique suffers from limitations similar to those of traditional Doppler because it can only accurately assess deformation in the plane incident with the ultrasound beam and requires prospective acquisition of dedicated images at high frame rate. B-mode speckle tracking, sometimes referred to as feature tracking, utilizes the movement of the coherent ultrasound backscatter speckle pattern within B-mode echocardiographic images to assess myocardial...

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“…In particular, these strain profiles reveal a severe loss of transmural strain heterogeneity in circumferential, longitudinal, and radial strains E CC , E LL , and E RR . The identification of deviations from baseline strains is clinically important to guide the optimal timing of clinical interventions, e.g., in asymptomatic severe mitral regurgitation [6] or in progressive heart failure [18]. …”

Section: Discussionmentioning

confidence: 99%

“…Marker techniques have been used successfully to identify acute changes in strain profiles, for example initiated by varying afterload [50] or by ventricular pacing [11]. However, the true strength of this technique lies in its permanent nature, which allows us to precisely quantify chronic changes, for example in response to mitral regurgitation [6] or myocardial infarction [9, 56]. Here, we utilize the transmural marker technique to characterize growth tensors and strains in the lateral left ventricular wall in response to myocardial infarction.…”

Section: Introductionmentioning

confidence: 99%

Kinematics of cardiac growth: In vivo characterization of growth tensors and strains

Tsamis

Cheng

Nguyen

et al. 2012

Journal of the Mechanical Behavior of Biomedical Materials

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Progressive growth and remodeling of the left ventricle are part of the natural history of chronic heart failure and strong clinical indicators for survival. Accompanied by changes in cardiac form and function, they manifest themselves in alterations of cardiac strains, fiber stretches, and muscle volume. Recent attempts to shed light on the mechanistic origin of heart failure utilize continuum theories of growth to predict the maladaptation of the heart in response to pressure or volume overload. However, despite a general consensus on the representation of growth through a second order tensor, the precise format of this growth tensor remains unknown. Here we show that infarct-induced cardiac dilation is associated with a chronic longitudinal growth, accompanied by a chronic thinning of the ventricular wall. In controlled in vivo experiments throughout a period of seven weeks, we found that the lateral left ventricular wall adjacent to the infarct grows longitudinally by more than 10%, thins by more than 25%, lengthens in fiber direction by more than 5%, and decreases its volume by more than 15%. Our results illustrate how a local loss of blood supply induces chronic alterations in structure and function in adjacent regions of the ventricular wall. We anticipate our findings to be the starting point for a series of in vivo studies to calibrate and validate constitutive models for cardiac growth. Ultimately, these models could be useful to guide the design of novel therapies, which allow us to control the progression of heart failure.

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Alterations in Transmural Myocardial Strain

Cited by 17 publications

References 38 publications

Early left ventricular regional contractile impairment in chronic mitral regurgitation occurs in a consistent, heterogeneous pattern

Early left ventricular regional contractile impairment in chronic mitral regurgitation occurs in a consistent, heterogeneous pattern

Myocardial Deformation Imaging

Kinematics of cardiac growth: In vivo characterization of growth tensors and strains

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