MRI-based prediction of adverse cardiac remodeling after murine myocardial infarction

Nrf2 attenuates the innate immune response after experimental myocardial infarction

BACKGROUND

There is compelling evidence implicating dysregulated inflammation in the mechanism of ventricular remodeling and heart failure (HF) after MI. The transcription factor nuclear factor erythroid-derived 2-like 2 (Nrf2, encoded by Nfe2l2) is a promising target in this context since it impedes transcriptional upregulation of pro-inflammatory cytokines and is anti-inflammatory in various murine models.

OBJECTIVES

We aimed to investigate the contribution of Nrf2 to the inflammatory response after experimental myocardial infarction (MI).

METHODS

We subjected Nrf2-/- mice and wild type (WT) controls to permanent left coronary artery (LCA) ligation. The inflammatory response was investigated with fluorescence-activated cell sorting (FACS) analysis of peripheral blood and heart cell suspensions, together with qRT-PCR of infarcted tissue for chemokines and their receptors. To investigate whether Nrf2-mediated transcription is a dedicated function of leukocytes, we interrogated publicly available RNA-sequencing (RNA-seq) data from mouse hearts after permanent LCA ligation for Nrf2-regulated gene (NRG) expression.

RESULTS

FACS analysis demonstrated a profoundly inflamed phenotype in the hearts of global Nrf2-/- mice as compared to WT mice after MI. Moreover, infarcted tissue from Nrf2-/- mice displayed higher expression of mRNA coding for inflammatory cytokines, chemokines, and their receptors, including IL-6, Ccl2, and Cxcr4. RNA-seq analysis showed upregulated NRG expression in WT mice after MI compared to naive mice, which was significantly higher in bioinformatically isolated CCR2+ cells.

CONCLUSIONS

Taken together, the results suggest that Nrf2 signalling in leukocytes, and possibly CCR2+ monocytes and monocyte-derived cardiac resident macrophages, may be potential targets to prevent post-MI ventricular remodeling.

Biomechanics of infarcted left Ventricle-A review of experiments

Myocardial infarction (MI) is one of leading diseases to contribute to annual death rate of 5% in the world. In the past decades, significant work has been devoted to this subject. Biomechanics of infarcted left ventricle (LV) is associated with MI diagnosis, understanding of remodelling, MI micro-structure and biomechanical property characterizations as well as MI therapy design and optimization, but the subject has not been reviewed presently. In the article, biomechanics of infarcted LV was reviewed in terms of experiments achieved in the subject so far. The concerned content includes experimental remodelling, kinematics and kinetics of infarcted LVs. A few important issues were discussed and several essential topics that need to be investigated further were summarized. Microstructure of MI tissue should be observed even carefully and compared between different methods for producing MI scar in the same animal model, and eventually correlated to passive biomechanical property by establishing innovative constitutive laws. More uniaxial or biaxial tensile tests are desirable on MI, border and remote tissues, and viscoelastic property identification should be performed in various time scales. Active contraction experiments on LV wall with MI should be conducted to clarify impaired LV pumping function and supply necessary data to the function modelling. Pressure-volume curves of LV with MI during diastole and systole for the human are also desirable to propose and validate constitutive laws for LV walls with MI.

Molecular Imaging of Myocardial Inflammation With Positron Emission Tomography Post-Ischemia: A Determinant of Subsequent Remodeling or Recovery

Inflammation after myocardial ischemia influences ventricular remodeling and repair and has emerged as a therapeutic target. Conventional diagnostic measurements address systemic inflammation but cannot quantify local tissue changes. Molecular imaging facilitates noninvasive assessment of leukocyte infiltration into damaged myocardium. Preliminary experience with ¹⁸F-labeled fluorodeoxyglucose ([¹⁸F]FDG) demonstrates localized inflammatory cell signal within the infarct territory as an independent predictor of subsequent ventricular dysfunction. Novel targeted radiotracers may provide additional insight into the enrichment of specific leukocyte populations. Challenges to wider implementation of inflammation imaging after myocardial infarction include accurate and reproducible quantification, prognostic value, and capacity to monitor inflammation response to novel treatment. This review describes myocardial inflammation following ischemia as a molecular imaging target and evaluates established and emerging radiotracers for this application. Furthermore, the potential role of inflammation imaging to provide prognostic information, support novel drug and therapeutic research, and assess biological response to cardiac disease is discussed.

MRI with gadofosveset: A potential marker for permeability in myocardial infarction

BACKGROUND AND AIMS

Acute ischemia is associated with myocardial endothelial damage and microvessel formation, resulting in leakage of plasma albumin into the myocardial extravascular space. In this study, we tested whether an albumin-binding intravascular contrast agent (gadofosveset) allows for improved quantification of myocardial permeability compared to the conventional extracellular contrast agent Gd-DTPA using late gadolinium enhancement (LGE) and T1 mapping in vivo.

METHODS

MI was induced in C57BL/6 mice (n = 6) and cardiac magnetic resonance imaging (CMR) was performed at 3, 10 and 21 days post-MI using Gd-DTPA and 24 h later using gadofosveset. Functional, LGE and T1 mapping protocols were performed 45 min post-injection of the contrast agent.

RESULTS

LGE images showed that both contrast agents provided similar measurements of infarct area at all time points following MI. Importantly, the myocardial R1 measurements after administration of gadofosveset were higher in the acute phase-day 3 (R1 [s-1] = 6.29 ± 0.29) compared to the maturation phase-days 10 and 21 (R1 [s-1] = 4.76 ± 0.30 and 4.48 ± 0.14), suggesting that the uptake of this agent could be used to stage myocardial remodeling. No differences in myocardial R1 were observed after administration of Gd-DTPA at different time points post-MI (R1 [s-1] = 3d: 3.77 ± 0.37; 10d: 2.74 ± 0.06; 21d: 3.35 ± 0.26). The MRI results were validated by ex vivo histology that showed albumin leakage in the myocardium in the acute phase and microvessel formation at later stages.

CONCLUSIONS

We demonstrate the merits of an albumin-binding contrast agent for monitoring changes in myocardial permeability between acute ischemia and chronic post-MI myocardial remodeling.

Is cardiac magnetic resonance necessary for prediction of left ventricular remodeling in patients with reperfused ST-segment elevation myocardial infarction?

As cardiac magnetic resonance imaging (CMR) has become widely used for evaluation of myocardial viability after acute myocardial infarction, the additional value of CMR parameters for prediction of left ventricle (LV) remodeling has been receiving interest. The aim of the study was to investigate the additional predictive value of CMR parameters for LV remodeling after successful reperfusion of ST-segment elevation myocardial infarction (STEMI) using multiple predictive models. LV remodeling was defined as ≥20% increase in end-diastolic volume at 6 month follow-up echocardiography. Using multiple stepwise regression analysis, conventional risk model was classified as following; model 1 (clinical factors), model 2 (model 1 + angiographic factors), model 3 (model 2 + echocardiographic factors) and CMR-added model; model 4 (model 3 + CMR factors). Among 262 enrolled patients, 25.1% showed LV remodeling. There were significant increments of c-statistics from the predictive model 1 to model 3 (AUC; 0.675 [0.60-0.75], 0.708 [0.64-0.78], 0.756 [0.69-0.82], respectively. all p < 0.05). However, model 4, which added the CMR variables, did not show any increase in predictive value compared with model 3 (AUC; 0.763 [0.70-0.83] versus 0.756 [0.69-0.82], p = 0.11). During the 28.2 months of median follow up, the incidence of hospitalization for heart failure was significantly higher in the patients with LV remodeling (6.1% vs. 0.5%, p = 0.02). CMR parameters did not provide incremental predictive value above the assessment by conventional echocardiography-based risk model in patients with STEMI.

Toll-like receptor 9 prevents cardiac rupture after myocardial infarction in mice independently of inflammation

We have reported that the Toll-like receptor 9 (TLR9) signaling pathway plays an important role in the development of pressure overload-induced inflammatory responses and heart failure. However, its role in cardiac remodeling after myocardial infarction has not been elucidated. TLR9-deficient and control C57Bl/6 wild-type mice were subjected to left coronary artery ligation. The survival rate 14 days postoperation was significantly lower in TLR9-deficient mice than that in wild-type mice with evidence of cardiac rupture in all dead mice. Cardiac magnetic resonance imaging showed no difference in infarct size and left ventricular wall thickness and function between TLR9-deficient and wild-type mice. There were no differences in the number of infiltrating inflammatory cells and the levels of inflammatory cytokine mRNA in infarct hearts between TLR9-deficient and wild-type mice. The number of α-smooth muscle actin (αSMA)-positive myofibroblasts and αSMA/Ki67-double-positive proliferative myofibroblasts was increased in the infarct and border areas in infarct hearts compared with those in sham-operated hearts in wild-type mice, but not in TLR9-deficient mice. The class B CpG oligonucleotide increased the phosphorylation level of NF-κB and the number of αSMA-positive and αSMA/Ki67-double-positive cells and these increases were attenuated by BAY1-7082, an NF-κB inhibitor, in cardiac fibroblasts isolated from wild-type hearts. The CpG oligonucleotide showed no effect on NF-κB activation or the number of αSMA-positive and αSMA/Ki67-double-positive cells in cardiac fibroblasts from TLR9-deficient hearts. Although the TLR9 signaling pathway is not involved in the acute inflammatory response in infarct hearts, it ameliorates cardiac rupture possibly by promoting proliferation and differentiation of cardiac fibroblasts.

Cell-specific effects of Nox2 on the acute and chronic response to myocardial infarction

Background

Increased reactive oxygen species (ROS) production is involved in the process of adverse cardiac remodeling and development of heart failure after myocardial infarction (MI). NADPH oxidase-2 (Nox2) is a major ROS source within the heart and its activity increases after MI. Furthermore, genetic deletion of Nox2 is protective against post-MI cardiac remodeling. Nox2 levels may increase both in cardiomyocytes and endothelial cells and recent studies indicate cell-specific effects of Nox2, but it is not known which of these cell types is important in post-MI remodeling.

Methods and results

We have generated transgenic mouse models in which Nox2 expression is targeted either to cardiomyocytes (cardio-Nox2TG) or endothelial cells (endo-Nox2TG). We here studied the response of cardio-Nox2TG mice, endo-Nox2TG mice and matched wild-type littermates (WT) to MI induced by permanent left coronary artery ligation up to 4 weeks. Initial infarct size assessed by magnetic resonance imaging (MRI) and cardiac dysfunction were similar among groups. Cardiomyocyte hypertrophy and interstitial fibrosis were augmented in cardio-Nox2TG compared to WT after MI and post-MI survival tended to be worse whereas endo-Nox2TG mice showed no significant difference compared to WT.

Conclusions

These results indicate that cardiomyocyte rather than endothelial cell Nox2 may have the more important role in post-MI remodeling.

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ROS contribute to adverse cardiac remodeling after myocardial infarction (MI).

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Nox2 is a major cardiac ROS source but with cell-specific effects.

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Increased Nox2 in cardiomyocytes augments hypertrophy and fibrosis post-MI.

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Increased Nox2 in endothelium has no significant effect on cardiac remodeling after MI.

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Cardiomyocyte Nox2 may have the more important role in post-MI remodeling.

Using MRI to predict future adverse cardiac remodelling in a male mouse model of myocardial infarction

Background

Mice are frequently used in research to examine outcomes of myocardial infarction (MI) and to investigate therapeutic interventions at an early pre-clinical stage. The MI model is generated by surgically occluding a major coronary artery, but natural variation in murine coronary anatomy can generate variable outcomes that will inevitably affect the accuracy of such investigations. The aim of this study was to use MRI to derive the most sensitive early variable that could be used to predict subsequent adverse cardiac remodelling in a male mouse model of MI.

Methods

Using a longitudinal study design, heart structure and function were evaluated using cardiac MRI at one week following surgical MI to generate the early measurements and again at four weeks, when the scar had matured. The primary variables measured at week one were left ventricular volumes at end systole (LV-ESV) and at end diastole (LV-EDV), infarct size, LV-cardiac mass, and ejection fraction (EF).

Results

Univariate and multiple regression analyses showed that LV-ESV at one week following MI could be used to accurately predict various parameters of adverse LV remodelling at four weeks post-MI. However, the highest correlation was between LV-ESV at one week following MI and LV-EDV at four weeks (r = 0.99; p < 0.0001), making LV-ESV at one week a valuable predictor variable of future adverse ventricular remodelling after MI.

Conclusion

Using MRI to determine LV-ESV at an early stage following MI enables a more robust analysis of potential therapeutic interventions to ameliorate adverse cardiac remodelling.

Cardiomyocyte and Vascular Smooth Muscle-Independent 11β-Hydroxysteroid Dehydrogenase 1 Amplifies Infarct Expansion, Hypertrophy, and the Development of Heart Failure After Myocardial Infarction in Male Mice

Global deficiency of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), an enzyme that regenerates glucocorticoids within cells, promotes angiogenesis, and reduces acute infarct expansion after myocardial infarction (MI), suggesting that 11β-HSD1 activity has an adverse influence on wound healing in the heart after MI. The present study investigated whether 11β-HSD1 deficiency could prevent the development of heart failure after MI and examined whether 11β-HSD1 deficiency in cardiomyocytes and vascular smooth muscle cells confers this protection. Male mice with global deficiency in 11β-HSD1, or with Hsd11b1 disruption in cardiac and vascular smooth muscle (via SM22α-Cre recombinase), underwent coronary artery ligation for induction of MI. Acute injury was equivalent in all groups. However, by 8 weeks after induction of MI, relative to C57Bl/6 wild type, globally 11β-HSD1-deficient mice had reduced infarct size (34.7 ± 2.1% left ventricle [LV] vs 44.0 ± 3.3% LV, P = .02), improved function (ejection fraction, 33.5 ± 2.5% vs 24.7 ± 2.5%, P = .03) and reduced ventricular dilation (LV end-diastolic volume, 0.17 ± 0.01 vs 0.21 ± 0.01 mL, P = .01). This was accompanied by a reduction in hypertrophy, pulmonary edema, and in the expression of genes encoding atrial natriuretic peptide and β-myosin heavy chain. None of these outcomes, nor promotion of periinfarct angiogenesis during infarct repair, were recapitulated when 11β-HSD1 deficiency was restricted to cardiac and vascular smooth muscle. 11β-HSD1 expressed in cells other than cardiomyocytes or vascular smooth muscle limits angiogenesis and promotes infarct expansion with adverse ventricular remodeling after MI. Early pharmacological inhibition of 11β-HSD1 may offer a new therapeutic approach to prevent heart failure associated with ischemic heart disease.

Bone marrow transplantation modulates tissue macrophage phenotype and enhances cardiac recovery after subsequent acute myocardial infarction

BACKGROUND

Bone marrow transplantation (BMT) is commonly used in experimental studies to investigate the contribution of BM-derived circulating cells to different disease processes. During studies investigating the cardiac response to acute myocardial infarction (MI) induced by permanent coronary ligation in mice that had previously undergone BMT, we found that BMT itself affects the remodelling response.

METHODS AND RESULTS

Compared to matched naive mice, animals that had previously undergone BMT developed significantly less post-MI adverse remodelling, infarct thinning and contractile dysfunction as assessed by serial magnetic resonance imaging. Cardiac rupture in male mice was prevented. Histological analysis showed that the infarcts of mice that had undergone BMT had a significantly higher number of inflammatory cells, surviving cardiomyocytes and neovessels than control mice, as well as evidence of significant haemosiderin deposition. Flow cytometric and histological analyses demonstrated a higher number of alternatively activated (M2) macrophages in myocardium of the BMT group compared to control animals even before MI, and this increased further in the infarcts of the BMT mice after MI.

CONCLUSIONS

The process of BMT itself substantially alters tissue macrophage phenotype and the subsequent response to acute MI. An increase in alternatively activated macrophages in this setting appears to enhance cardiac recovery after MI.

Assessment of Myocardial Remodeling Using an Elastin/Tropoelastin Specific Agent with High Field Magnetic Resonance Imaging (MRI)

Background

Well-defined inflammation, proliferation, and maturation phases orchestrate the remodeling of the injured myocardium after myocardial infarction (MI) by controlling the formation of new extracellular matrix. The extracellular matrix consists mainly of collagen but also fractions of elastin. It is thought that elastin is responsible for maintaining elastic properties of the myocardium, thus reducing the risk of premature rupture. An elastin/tropoelastin–specific contrast agent (Gd-ESMA) was used to image tropoelastin and mature elastin fibers for in vivo assessment of extracellular matrix remodeling post-MI.

Methods and Results

Gd-ESMA enhancement was studied in a mouse model of myocardial infarction using a 7 T MRI scanner and results were compared to those achieved after injection of a nonspecific control contrast agent, gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In the infarcted tissue, Gd-ESMA uptake (measured as R1 relaxation rate) steadily increased from day 3 to day 21 as a result of the synthesis of elastin/tropoelastin. R1 values were in good agreement with histological findings. A similar R1 behavior was observed in the remote myocardium. No mature cross-linked elastin was found at any time point. In contrast, Gd-DTPA uptake was only observed in the infarct with no changes in R1 values between 3 and 21 days post-MI.

Conclusions

We demonstrate the feasibility of in vivo imaging of extracellular matrix remodeling post-MI using a tropoelastin/elastin binding MR contrast agent, Gd-ESMA. We found that tropoelastin is the main contributor to the increased MRI signal at late stages of MI where its augmentation in areas of infarction was in good agreement with the R1 increase.

Small animal cardiovascular MR imaging and spectroscopy

The use of MR imaging and spectroscopy for studying cardiovascular disease processes in small animals has increased tremendously over the past decade. This is the result of the remarkable advances in MR technologies and the increased availability of genetically modified mice. MR techniques provide a window on the entire timeline of cardiovascular disease development, ranging from subtle early changes in myocardial metabolism that often mark disease onset to severe myocardial dysfunction associated with end-stage heart failure. MR imaging and spectroscopy techniques play an important role in basic cardiovascular research and in cardiovascular disease diagnosis and therapy follow-up. This is due to the broad range of functional, structural and metabolic parameters that can be quantified by MR under in vivo conditions non-invasively. This review describes the spectrum of MR techniques that are employed in small animal cardiovascular disease research and how the technological challenges resulting from the small dimensions of heart and blood vessels as well as high heart and respiratory rates, particularly in mice, are tackled.

Dysfunction of the CNS-heart axis in mouse models of Huntington's disease

Cardiac remodelling and contractile dysfunction occur during both acute and chronic disease processes including the accumulation of insoluble aggregates of misfolded amyloid proteins that are typical features of Alzheimer's, Parkinson's and Huntington's disease (HD). While HD has been described mainly as a neurological disease, multiple epidemiological studies have shown that HD patients exhibit a high incidence of cardiovascular events leading to heart failure, and that this is the second highest cause of death. Given that huntingtin is ubiquitously expressed, cardiomyocytes may be at risk of an HD-related dysfunction. In mice, the forced expression of an expanded polyQ repeat under the control of a cardiac specific promoter led to severe heart failure followed by reduced lifespan. However the mechanism leading to cardiac dysfunction in the clinical and pre-clinical HD settings remains unknown. To unravel this mechanism, we employed the R6/2 transgenic and HdhQ150 knock-in mouse models of HD. We found that pre-symptomatic animals developed connexin-43 relocation and a significant deregulation of hypertrophic markers and Bdnf transcripts. In the symptomatic animals, pronounced functional changes were visualised by cardiac MRI revealing a contractile dysfunction, which might be a part of dilatated cardiomyopathy (DCM). This was accompanied by the re-expression of foetal genes, apoptotic cardiomyocyte loss and a moderate degree of interstitial fibrosis. To our surprise, we could identify neither mutant HTT aggregates in cardiac tissue nor a HD-specific transcriptional dysregulation, even at the end stage of disease. We postulate that the HD-related cardiomyopathy is caused by altered central autonomic pathways although the pathogenic effects of mutant HTT acting intrinsically in the heart may also be a contributing factor.

Huntington's disease (HD) is a neurodegenerative disorder for which the mutation results in an extra-long tract of glutamines that causes the huntingtin protein to aggregate. It is characterized by neurological symptoms and brain pathology that is associated with nuclear and cytoplasmic aggregates and with transcriptional dysregulation. Despite the fact that HD has been recognized principally as a neurological disease, there are multiple epidemiological studies showing that HD patients exhibit a high rate of cardiovascular events leading to heart failure. To unravel the cause of cardiac dysfunction in HD models, we employed a wide range of molecular and physiological methods using two well established genetic mouse models of this disease. We found that pre-symptomatic animals developed aberrant gap junction channel expression and a significant deregulation of hypertrophic markers that may predispose them to arrhythmia and an overall change in cardiac function. These changes were accompanied by the re-expression of foetal genes, apoptotic cardiomyocyte loss and a moderate degree of interstitial fibrosis in the symptomatic animals. Surprisingly, we could identify neither mutant HTT aggregates in cardiac tissue nor a HD-specific transcriptional dysregulation. Therefore, we conclude that the HD-related cardiomyopathy could be driven by altered central autonomic pathways.

The role of 1.5 tesla MRI and anesthetic regimen concerning cardiac analysis in mice with cardiomyopathy

Accurate assessment of left ventricular function in rodent models is essential for the evaluation of new therapeutic approaches for cardiac diseases. In our study, we provide new insights regarding the role of a 1.5 Tesla (T) magnetic resonance imaging (MRI) device and different anesthetic regimens on data validity. As dedicated small animal MRI and echocardiographic devices are not broadly available, we evaluated whether monitoring cardiac function in small rodents with a clinical 1.5 T MRI device is feasible. On a clinical electrocardiogram (ECG) synchronized 1.5 T MRI scanner we therefore studied cardiac function parameters of mice with chronic virus-induced cardiomyopathy. Thus, reduced left ventricular ejection fraction (LVEF) could be verified compared to healthy controls. However, our results showed a high variability. First, anesthesia with medetomidine, midazolam and fentanyl (MMF) led to depressed cardiac function parameters and more variability than isoflurane gas inhalation anesthesia, especially at high concentrations. Furthermore, calculation of an average ejection fraction value from sequenced scans significantly reduced the variance of the results. To sum up, we introduce the clinical 1.5 T MRI device as a new tool for effective analysis of left ventricular function in mice with cardiomyopathy. Besides, we suggest isoflurane gas inhalation anesthesia at high concentrations for variance reduction and recommend calculation of an average ejection fraction value from multiple sequenced MRI scans to provide valid data and a solid basis for further clinical testing.

Thymosin β4 coated nanofiber scaffolds for the repair of damaged cardiac tissue

After a cardiac event, proper treatment and care of the damaged tissue is crucial in restoring optimal cardiac function and preventing future cardiac events. Recently, thymosin β4 has been found to play a vital role in cardiac cell health and development by regulating angiogenesis, inflammatory responses, and wound healing. We proposed that defined poly(ϵ-caprolactone) (PCL) nanoscaffolds coated with thymosin β4 could efficiently differentiate murine-derived cardiomyocytes into functioning cardiac tissue. PCL nanoscaffolds were developed through electrospinning technology, and subsequently coated with a thymosin β4 solution. Cardiomyocytes were seeded on coated and uncoated nanoscaffolds and observed for six days via fluorescent and electron microscopy. Our results demonstrated a robust growth and differentiation of cardiomyocytes on coated nanoscaffolds compared with uncoated, showing potential for nanoscaffold-mediated cardiac cell replacement in vivo after an MI or other cardiac event.

High-frequency speckle tracking echocardiography in the assessment of left ventricular function and remodeling after murine myocardial infarction

The objectives of this study were to assess the feasibility and accuracy of high-frequency speckle tracking echocardiography (STE) in a murine model of myocardial infarction (MI). STE is used clinically to quantify global and regional cardiac function, but its application in mice is challenging because of the small cardiac size and rapid heart rates. A high-frequency micro-ultrasound system with STE (Visualsonics Vevo 2100) was compared against magnetic resonance imaging (MRI) for the assessment of global left ventricular (LV) size and function after murine MI. Animals subjected to coronary ligation (n = 46) or sham ligation (n = 27) were studied 4 wk postoperatively. Regional and global deformation were also assessed. STE-derived LV ejection fraction (EF) and mass correlated well with MRI indexes (r = 0.93, 0.77, respectively; P < 0.001), as did STE-derived mass with postmortem values (r = 0.80, P < 0.001). Higher STE-derived volumes correlated positively with MRI-derived infarct size (P < 0.01). Global strain parameters were significantly reduced after MI (all P < 0.001) and strongly correlated with LV mass and MRI-derived infarct size as promising surrogates for the extent of remodeling and infarction, respectively (both P < 0.05). Regional strain analyses showed that radial strain and strain rate were relatively preserved in anterior basal segments after MI compared with more apical segments (P < 0.001); however, longitudinal strain and strain rate were significantly impaired both basally and distally (P < 0.001). Strain-derived parameters of dyssynchrony were significantly increased in the MI group (P < 0.01). Analysis time for STE was 210 ± 45 s with acceptable inter- and intraobserver variability. In conclusion, high-frequency STE enables quantitative assessment of regional and global function in the remodeling murine LV after MI.