Assessment of segmental myocardial viability using regional 2-dimensional strain echocardiography

Differences in radiation-induced heart dysfunction in male versus female rats

PURPOSE

Radiation therapy remains part of the standard of care for breast, lung, and esophageal cancers. While radiotherapy improves local control and survival, radiation-induced heart dysfunction is a common side effect of thoracic radiotherapy. Cardiovascular dysfunction can also result from non-therapeutic total body radiation exposures. Numerous studies have evaluated the relationship between radiation dose to the heart and cardiotoxicity, but relatively little is known about whether there are differences based on biological sex in radiation-induced heart dysfunction (RIHD).

MATERIALS AND METHODS

We evaluated whether male and female inbred Dahl SS rats display differences in RIHD following delivery of 24 Gy in a single fraction to the whole heart using a 1.5 cm beam size (collimater). We also compared the 2.0 cm vs. 1.5 cm collimator in males. Pleural and pericardial effusions and normalized heart weights were measured, and echocardiograms were performed.

RESULTS

Female SS rats displayed more severe RIHD relative to age-matched SS male rats. Normalized heart weight was significantly increased in females, but not in males. A total of 94% (15/16) of males and 55% (6/11) of females survived 5 months after completion of radiotherapy (p < .01). Among surviving rats, 100% of females and 14% of males developed moderate-to-severe pericardial effusions at 5 months. Females demonstrated increased pleural effusions, with the mean normalized pleural fluid volume for females and males being 56.6 mL/kg ± 12.1 and 10.96 mL/kg ± 6.4 in males (p = .001), respectively. Echocardiogram findings showed evidence of heart failure, which was more pronounced in females. Because age-matched female rats have smaller lungs, a higher percentage of the total lung was treated with radiation in females than males using the same beam size. After using a larger 2 cm beam in males which results in higher lung exposure, there was not a significant difference between males and females in terms of the development of moderate-to-severe pericardial effusions or pleural effusions. Treatment of males with a 2 cm beam resulted in comparable increases in LV mass and reductions in stroke volume to female rats treated with a 1.5 cm beam.

CONCLUSION

Together, these results illustrate that there are differences in radiation-induced cardiotoxicity between male and female SS rats and add to the data that lung radiation doses, in addition to other factors, may play an important role in cardiac dysfunction following heart radiation exposure. These factors may be important to factor into future mitigation studies of radiation-induced cardiotoxicity.

Mechano-growth factor E-domain modulates cardiac contractile function through 14-3-3 protein interactomes

In the heart, alternative splicing of the igf-I gene produces two isoforms: IGF-IEa and IGF-IEc, (Mechano-growth factor, MGF). The sequence divergence between their E-domain regions suggests differential isoform function. To define the biological actions of MGF's E-domain, we performed in silico analysis of the unique C-terminal sequence and identified a phosphorylation consensus site residing within a putative 14-3-3 binding motif. To test the functional significance of Ser 18 phosphorylation, phospho-mimetic (S/E¹⁸) and phospho-null (S/A¹⁸) peptides were delivered to mice at different doses for 2 weeks. Cardiovascular function was measured using echocardiography and a pressure-volume catheter. At the lowest (2.25 mg/kg/day) and highest (9 mg/kg/day) doses, the peptides produced a depression in systolic and diastolic parameters. However, at 4.5 mg/kg/day the peptides produced opposing effects on cardiac function. Fractional shortening analysis also showed a similar trend, but with no significant change in cardiac geometry. Microarray analysis discovered 21 genes (FDR p < 0.01), that were expressed accordant with the opposing effects on contractile function at 4.5 mg/kg/day, with the nuclear receptor subfamily 4 group A member 2 (Nr4a2) identified as a potential target of peptide regulation. Testing the regulation of the Nr4a family, showed the E-domain peptides modulate Nr4a gene expression following membrane depolarization with KCl in vitro. To determine the potential role of 14-3-3 proteins, we examined 14-3-3 isoform expression and distribution. 14-3-3γ localized to the myofilaments in neonatal cardiac myocytes, the cardiac myocytes and myofilament extracts from the adult heart. Thermal shift analysis of recombinant 14-3-3γ protein showed the S/A¹⁸ peptide destabilized 14-3-3γ folding. Also, the S/A¹⁸ peptide significantly inhibited 14-3-3γ's ability to interact with myosin binding protein C (MYPC3) and phospholamban (PLN) in heart lysates from dobutamine injected mice. Conversely, the S/E¹⁸ peptide showed no effect on 14-3-3γ stability, did not inhibit 14-3-3γ's interaction with PLN but did inhibit the interaction with MYPC3. Replacing the glutamic acid with a phosphate group on Ser 18 (pSer¹⁸), significantly increased 14-3-3γ protein stability. We conclude that the state of Ser 18 phosphorylation within the 14-3-3 binding motif of MGF's E-domain, modulates protein-protein interactions within the 14-3-3γ interactome, which includes proteins involved in the regulation of contractile function.

Real-time three-dimensional echocardiography and two-dimensional speckle tracking imaging in the evaluation of left atrial function in patients with triple-vessel coronary artery disease without myocardial infarction

OBJECTIVE

To evaluate left atrial function in patients with triple-vessel disease (TVD) without myocardial infarction by real-time three-dimensional echocardiography (RT-3DE) and two-dimensional speckle tracking imaging (2D-STE).

METHODS

Sixty patients with coronary artery disease (CAD) without myocardial infarction were classified into two groups in accordance with the coronary angiography results: group B (all triple-vessel stenosis ≥ 50% and < 75%) and group C (all triple-vessel stenosis ≥ 75%). Thirty healthy individuals were selected as group A. LA volume related parameters including left atrial maximum volume index (LAVImax), LA passive and active ejection fraction (LAPEF, LAAEF) and LA total ejection fraction (LATEF) were measured by RT-3DE. The global peak atrial longitudinal systolic strain (LASRs), early and late diastolic LA strain (LASRe and LASRa) rates were measured by 2D-STE.

RESULTS

We found statistically significant differences between 2D-STE and RT-3DE related parameters of these three groups. Furthermore, in groups B and C, N-terminal fragment brain natriuretic peptides (NT-pro-BNP) and left ventricular end-diastolic pressure (LVEDP) were found to be significantly correlated with LASRs and LASRa. And NT-pro-BNP had a moderate correlation with LVEDP.

CONCLUSIONS

2D-STE and RT-3DE can assess the LA function in patients with TVD without myocardial infarction. And LA strain values may provide additional information for predicting increased LVEDP and NT-pro-BNP.

Changes in Global Left Ventricular Myocardial Work Indices and Stunning Detection 3 Months After ST-Segment Elevation Myocardial Infarction

Global left ventricular (LV) myocardial work (MW) indices (GLVMWI) are derived from speckle tracking echocardiographic strain data in combination with non-invasive blood pressure measurements. Changes in global work index (GWI), global constructive work (GCW), global wasted work (GWW) and global work efficiency (GWE) after ST-segment elevation myocardial infarction (STEMI) have not been explored. The aim of present study was to assess the evolution of GLVMWI in STEMI patients from baseline (index infarct) to 3 months' follow-up. Three-hundred and fifty patients (265 men; mean age 61 ± 10 years) with STEMI treated with primary percutaneous coronary intervention (PCI) and guideline-based medical therapy were retrospectively evaluated. Clinical variables, conventional echocardiographic measures and GLVMWI were recorded at baseline within 48 hours post-primary PCI and 3 months' follow-up. LV ejection fraction (from 54 ± 10% to 57 ± 10%, p < 0.001), GWI (from 1449 ± 451 mm Hg% to 1953 ± 492 mm Hg%, p < 0.001), GCW (from 1624 ± 519 mm Hg% to 2228 ± 563 mm Hg%, p < 0.001) and GWE (from 93% (interquartile range (IQR) 86%-95%) to 95% (IQR 91%-96%), p < 0.001) improved significantly at 3 months' follow-up with no significant difference in GWW (from 101 mm Hg% (IQR 63-155 mm Hg%) to 96 mm Hg% (IQR 64-155 mm Hg%); p = 0.535). On multivariable linear regression analysis, lower values of troponin T at baseline, increase in systolic blood pressure and improvement in LV global longitudinal strain were independently associated with higher GWI and GCW at 3 months' follow-up. In conclusion, the evolution of GWI, GCW and GWE in STEMI patients may reflect myocardial stunning, whereas the stability in GWW may reflect permanent myocardial damage and the development of non-viable scar tissue.

Acquired Immunity Is Not Essential for Radiation-Induced Heart Dysfunction but Exerts a Complex Impact on Injury

While radiation therapy (RT) can improve cancer outcomes, it can lead to radiation-induced heart dysfunction (RIHD) in patients with thoracic tumors. This study examines the role of adaptive immune cells in RIHD. In Salt-Sensitive (SS) rats, image-guided whole-heart RT increased cardiac T-cell infiltration. We analyzed the functional requirement for these cells in RIHD using a genetic model of T- and B-cell deficiency (interleukin-2 receptor gamma chain knockout (IL2RG-/-)) and observed a complex role for these cells. Surprisingly, while IL2RG deficiency conferred protection from cardiac hypertrophy, it worsened heart function via echocardiogram three months after a large single RT dose, including increased end-systolic volume (ESV) and reduced ejection fraction (EF) and fractional shortening (FS) (p < 0.05). Fractionated RT, however, did not yield similarly increased injury. Our results indicate that T cells are not uniformly required for RIHD in this model, nor do they account for our previously reported differences in cardiac RT sensitivity between SS and SS.BN3 rats. The increasing use of immunotherapies in conjunction with traditional cancer treatments demands better models to study the interactions between immunity and RT for effective therapy. We present a model that reveals complex roles for adaptive immune cells in cardiac injury that vary depending on clinically relevant factors, including RT dose/fractionation, sex, and genetic background.

Differences in Expression of Mitochondrial Complexes Due to Genetic Variants May Alter Sensitivity to Radiation-Induced Cardiac Dysfunction

Radiation therapy is received by over half of all cancer patients. However, radiation doses may be constricted due to normal tissue side effects. In thoracic cancers, including breast and lung cancers, cardiac radiation is a major concern in treatment planning. There are currently no biomarkers of radiation-induced cardiotoxicity. Complex genetic modifiers can contribute to the risk of radiation-induced cardiotoxicities, yet these modifiers are largely unknown and poorly understood. We have previously reported the SS (Dahl salt-sensitive/Mcwi) rat strain is a highly sensitized model of radiation-induced cardiotoxicity compared to the more resistant Brown Norway (BN) rat strain. When rat chromosome 3 from the resistant BN rat strain is substituted into the SS background (SS.BN3 consomic), it significantly attenuates radiation-induced cardiotoxicity, demonstrating inherited genetic variants on rat chromosome 3 modify radiation sensitivity. Genes involved with mitochondrial function were differentially expressed in the hearts of SS and SS.BN3 rats 1 week after radiation. Here we further assessed differences in mitochondria-related genes between the sensitive SS and resistant SS.BN3 rats. We found mitochondrial-related gene expression differed in untreated hearts, while no differences in mitochondrial morphology were seen 1 week after localized heart radiation. At 12 weeks after localized cardiac radiation, differences in mitochondrial complex protein expression in the left ventricles were seen between the SS and SS.BN3 rats. These studies suggest that differences in mitochondrial gene expression caused by inherited genetic variants may contribute to differences in sensitivity to cardiac radiation.

Mapping genetic modifiers of radiation-induced cardiotoxicity to rat chromosome 3

Radiation therapy is used in ~50% of cancer patients to reduce the risk of recurrence and in some cases improve survival. Despite these benefits, doses can be limited by toxicity in multiple organs, including the heart. The underlying causes and biomarkers of radiation-induced cardiotoxicity are currently unknown, prompting the need for experimental models with inherent differences in sensitivity and resistance to the development of radiation-induced cardiotoxicity. We have identified the parental SS (Dahl salt-sensitive/Mcwi) rat strain to be a highly-sensitized model of radiation-induced cardiotoxicity. In comparison, substitution of rat chromosome 3 from the resistant BN (Brown Norway) rat strain onto the SS background (SS-3BN consomic) significantly attenuated radiation-induced cardiotoxicity. SS-3BN rats had less radiation-induced cardiotoxicity than SS rats, as measured by survival, pleural and pericardial effusions, echocardiogram parameters, and histological damage. Mast cells, previously shown to have predominantly protective roles in radiation-induced cardiotoxicity, were increased in the more resistant SS-3BN hearts postradiation. RNA sequencing from SS and SS-3BN hearts at 1 wk postradiation revealed 5,098 differentially expressed candidate genes across the transcriptome and 350 differentially expressed genes on rat chromosome 3, which coincided with enrichment of multiple pathways, including mitochondrial dysfunction, sirtuin signaling, and ubiquitination. Upstream regulators of enriched pathways included the oxidative stress modulating transcription factor, Nrf2, which is located on rat chromosome 3. Nrf2 target genes were also differentially expressed in the SS vs. SS-3BN consomic hearts postradiation. Collectively, these data confirm the existence of heritable modifiers in radiation-induced cardiotoxicity and provide multiple biomarkers, pathways, and candidate genes for future analyses. NEW & NOTEWORTHY This novel study reveals that heritable genetic factors have the potential to modify normal tissue sensitivity to radiation. Gene variant(s) on rat chromosome 3 can contribute to enhanced cardiotoxicity displayed in the SS rats vs. the BN and SS-3BN consomic rats. Identifying genes that lead to understanding the mechanisms of radiation-induced cardiotoxicity represents a novel method to personalize radiation treatment, as well as predict the development of radiation-induced cardiotoxicity.

Determinants of Myocardial Strain in Experimental Chronic Myocardial Infarction

We evaluated the relationships between regional myocardial strain measured by speckle tracking echocardiography and viability, fibrosis, hypertrophy and oxygen consumption in the infarcted or remote myocardium in a pig model of chronic myocardial infarction (MI). Thirteen farm pigs with surgical occlusion of the left anterior descending coronary artery and five sham-operated pigs were studied 3 mo post-MI. Computed tomography revealed significant left ventricle remodeling. Reduced radial or circumferential strain identified areas of transmural infarction (area under the curve: 0.82 and 0.79, respectively). In the remote non-infarcted area, radial strain correlated inversely with the amount of fibrosis (r = -0.66, p = 0.04) and myocyte hypertrophy (r = -0.68, p = 0.03). Radial strain rate inversely correlated with myocardial resting oxygen consumption assessed with ¹¹C-labeled acetate positron emission tomography (r = -0.71, p = 0.006). In conclusion, myocardial strain and strain rate reflect fibrosis, hypertrophy and oxygen consumption of the remote areas after MI.

Cardiac Imaging in the Diagnosis of Coronary Artery Disease

Coronary artery disease (CAD) continues to be a leading cause of morbidity and mortality worldwide. Although invasive coronary angiography has previously been the gold standard in establishing the diagnosis of CAD, there is a growing shift to more appropriately use the cardiac catheterization laboratory to perform interventional procedures once a diagnosis of CAD has been established by noninvasive imaging modalities rather than using it primarily as a diagnostic facility to confirm or refute CAD. With ongoing technological advancements, noninvasive imaging plays a pre-eminent role in not only diagnosing CAD but also informing the choice of appropriate therapies, establishing prognosis, all while containing costs and providing value-based care. Multiple imaging modalities are available to evaluate patients suspected of having coronary ischemia, such as stress electrocardiography, stress echocardiography, single-photon emission computed tomography myocardial perfusion imaging, positron emission tomography, coronary computed tomography (CT) angiography, and magnetic resonance imaging. These imaging modalities can variably provide functional and anatomical delineation of coronary stenoses and help guide appropriate therapy. This review will discuss their advantages and limitations and their usage in the diagnostic pathway for patients with CAD. We also discuss newer technologies such as CT fractional flow reserve, CT angiography with perfusion, whole-heart coronary magnetic resonance angiography with perfusion, which can provide both anatomical as well as functional information in the same test, thus obviating the need for multiple diagnostic tests to obtain a comprehensive assessment of both, plaque burden and downstream ischemia. Recognizing that clinicians have a multitude of tests to choose from, we provide an underpinning of the principles of ischemia detection by these various modalities, focusing on anatomy vs physiology, the database justifying their use, their prognostic capabilities and lastly, their appropriate and judicious use in this era of patient-centered, cost-effective imaging.

2D speckle tracking echocardiography for the assessment of regional contractile reserve after myocardial infarction

AIMS

To assess whether quantitative resting assessment of local myocardial function by 2D speckle tracking echocardiography may be helpful for the evaluation of myocardial viability in patients after ST-elevation myocardial infarction (STEMI) and for the prediction of left ventricular function recovery after 12-month follow-up.

METHODS

The study group comprised 96 patients with first STEMI treated with successful primary percutaneous coronary intervention. Seven to 12 days after STEMI, all patients underwent resting echocardiography and low-dose dobutamine stress echocardiography (LDDSE) with visual assessment of contractile reserve which was the reference method for the evaluation of myocardial viability. After 12 months resting echocardiography with visual assessment of functional recovery was performed. Subsequently, acquired images were analyzed off-line using 2D speckle tracking echocardiography algorithm. Measurements included peak systolic longitudinal and transverse strain (SLS/STS), peak longitudinal and transverse strain (PLS/PTS), systolic longitudinal and transverse strain rate (SLSR/STSR) at baseline and after 12 months.

RESULTS

All analyzed longitudinal parameters of strain had a very good diagnostic value, while transverse parameters had only good diagnostic value for predicting myocardial viability defined on the basis of LDDSE. Moreover, SLS and PLS had good, whereas SLSR only satisfactory diagnostic value for predicting function recovery after 12-month follow-up.

CONCLUSIONS

2D speckle tracking analysis applied during resting echocardiography can be helpful for the prediction of myocardial viability and functional recovery in patients after STEMI. Longitudinal strain parameters allow the prediction of local contractile reserve with SLS showing best correlation with DSE results functional recovery after 12-month follow-up.

Assessment of Left Ventricular Myocardial Viability by 3-Dimensional Speckle-Tracking Echocardiography in Patients With Myocardial Infarction

OBJECTIVES

To determine whether 3-dimensional (3D) speckle-tracking echocardiography could provide a new way to assess myocardial viability in patients with myocardial infarction (MI).

METHODS

Forty-five patients with MI underwent routine echocardiography, 2-dimensional (2D) speckle-tracking echocardiography, and 3D speckle-tracking echocardiography. Radionuclide myocardial perfusion/metabolic imaging was used as a reference standard to define viable and nonviable myocardia.

RESULTS

Among 720 myocardial segments in 45 patients, 368 showed abnormal motion on routine echocardiography; 204 of 368 were categorized as viable on single-photon emission computed tomography/positron emission tomography (SPECT/PET), whereas 164 were defined as nonviable; 300 normal segments on SPECT/PET among 352 segments without abnormal motion on routine echocardiography were categorized as a control group. The radial, longitudinal, 3D, and area strain on 3D speckle-tracking echocardiography had significant differences between control and nonviable groups (P < .001), whereas none of the parameters had significant differences between control and viable groups. There were no significant differences in circumferential, radial, and longitudinal peak systolic strain from 2D speckle-tracking echocardiography between viable and nonviable groups. Although there was no significant difference in circumferential strain between the groups, radial and longitudinal strain from 3D speckle-tracking echocardiography decreased significantly in the nonviable group. Moreover, 3D and area strain values were lower in the nonviable segments than the viable segments. By receiver operating characteristic analysis, radial strain from 3D speckle-tracking echocardiography with a cutoff of 11.1% had sensitivity of 95.1% and specificity of 53.4% for viable segments; longitudinal strain with a cutoff of 14.3% had sensitivity of 65.2% and specificity of 65.7%; 3D strain with a cutoff of 17.4% had sensitivity of 70.6% and specificity of 77.2%; and area strain with a cutoff of 23.2% had sensitivity of 91.5% and specificity of 82.8%.

CONCLUSIONS

Three-dimensional speckle-tracking echocardiography might have potential for detection of myocardial viability in patients with cardiac dysfunction due to MI.

Circumferential Strain Can Be Used to Detect Lipopolysaccharide-Induced Myocardial Dysfunction and Predict the Mortality of Severe Sepsis in Mice

BACKGROUND

Sepsis-induced myocardial dysfunction is a common and severe complication of septic shock. However, conventional echocardiography often fails to reveal myocardial depression in severe sepsis. Recently, strain measurements based on speckle tracking echocardiography (STE) have been used to evaluate cardiac function.

AIMS

To investigate the role of STE in detecting lipopolysaccharide (LPS)-induced cardiac dysfunction, M-mode and 2-D echocardiography were used in LPS-treated mice.

METHODS

The mice were treated with a 10mg/kg (n = 10), 20mg/kg (n = 10) or 25mg/kg LPS (n = 30) to induce cardiac dysfunction. Subsequently, the ejection fraction (EF) and fractional shortening (FS) were measured with standard M-mode tracings, whereas the circumferential (Scirc) and radial strain (Srad) were measured with STE. Serum biochemical and cardiac histopathological examinations were performed to assess sepsis-induced myocardial injury.

RESULTS

20mg/kg LPS resulted in more deterioration, myocardial damage and cardiac contractile dysfunction based on serum biochemical and histological examinations. The mice that were subjected to 20mg/kg LPS exhibited reduced Scirc but no reduction in Srad, whereas on conventional echocardiography, the ejection fraction (EF) and fractional shortening (FS) were similar in the 10mg/kg and 20mg/kg groups. Moreover, Scirc was positively correlated with body temperature in the mice at 20 h after LPS injection (r = 0.746, p = 0.001), but no significant correlation was observed between Srad and body temperature (r = 0.356, p = 0.123). Moreover, the mice with high Scirc (-5.9% to -10.4%) exhibited reduced mortality following the administration of 25mg/kg LPS (p = 0.03) compared with the low-strain group (-2% to -5.9%).

CONCLUSIONS

Taken together, our findings indicate that circumferential strain is a specific and reliable indicator for evaluating LPS-induced cardiac dysfunction in mice.

Early prediction of myocardial viability after acute myocardial infarction by two-dimensional speckle tracking imaging

Background

Identifying the transmural extent of myocardial necrosis and the degree of myocardial viability in acute myocardial infarction (AMI) is important clinically. The aim of this study was to assess myocardial viability using two-dimensional speckle tracking imaging (2D-STI) in patients with AMI.

Methods

2D-STI was performed at initial presentation, three days, and six months after primary percutaneous coronary intervention (PCI) in 30 patients with AMI, who had a left anterior descending coronary artery (LAD) culprit lesion. In addition, 20 patients who had minimal stenotic lesions (< 30% stenosis) on coronary angiography were also included in the control group. At six months dobutamine echocardiography was performed for viability assessment in seven segments of the LAD territory. According to the recovery of wall motion abnormality, segments were classified as viable or non-viable.

Results

A total of 131 segments were viable, and 44 were nonviable. Multivariate analysis revealed significant differences between the viable and nonviable segments in the peak systolic strain, the peak systolic strain rate at initial presentation, and peak systolic strain rate three days after primary PCI. Among these, the initial peak systolic strain rate had the highest predictive value for myocardial viability (hazard ratio: 31.22, P < 0.01).

Conclusions

2D-STI is feasible for assessing myocardial viability, and the peak systolic strain rate might be the most reliable predictor of myocardial viability in patients with AMI.

Strain Analysis in the Detection of Myocardial Infarction at the Acute and Chronic Stages

BACKGROUND

Myocardial ischemia causes contractile dysfunction in ischemic, stunned, and tethered regions with larger infarcted zones having a negative prognostic impact on patients' outcomes. To distinguish the infarcted myocardium from the other regions, we investigated the diagnostic potential of circumferential strain (CS) and radial strain (RS) during the acute and chronic stages of myocardial infarction.

METHODS

Ten pigs underwent 90-minute occlusion of the left anterior descending artery, followed by reperfusion. Echocardiography was performed at baseline, after 90-minute occlusion, and at 2 hours, 30, and 60 days postreperfusion. CS and RS were measured using speckle tracking echocardiography. Subsequently, the pigs were sacrificed, and histological analysis for infarct size was performed.

RESULTS

After 90-minute occlusion, reduced strains were detected for all segments (infarcted anterior wall - baseline: CS: -17.6 ± 5.7%, RS: 54.4 ± 16.9%; 90 min: CS: -10.3 ± 3.0%, RS: 23.3 ± 7.0%; tethered posterior wall - baseline: CS: -18.4 ± 3.5%, RS: 68.7 ± 21.1%; 90 min: CS: -10.7 ± 6.4%, RS: 34.5 ± 14.7%, P < 0.001). However, postsystolic shortening was detected only in the infarcted segments, and the time-to-peak CS was 25% longer (P < 0.05). At 30 and 60 days postreperfusion, time-to-peak CS could only detect large scars in the anterior and anterior-septum walls (P < 0.05), while peak CS also detected smaller scars in the lateral wall (P < 0.05). RS failed to distinguish between normal, stunned/tethered, and infarcted myocardium.

CONCLUSIONS

During occlusion and 2 hours postreperfusion, time-to-peak CS could distinguish between infarcted and stunned/tethered myocardial segments, while at 30 and 60 days postreperfusion, peak CS was the best detector of infarction.

Simvastatin mitigates increases in risk factors for and the occurrence of cardiac disease following 10 Gy total body irradiation

The ability of simvastatin to mitigate the increases in risk factors for and the occurrence of cardiac disease after 10 Gy total body irradiation (TBI) was determined. This radiation dose is relevant to conditioning for stem cell transplantation and threats from radiological terrorism. Male rats received single dose TBI of 10 Gy. Age-matched, sham-irradiated rats served as controls. Lipid profile, heart and liver morphology and cardiac mechanical function were determined for up to 120 days after irradiation. TBI resulted in a sustained increase in total- and LDL-cholesterol (low-density lipoprotein-cholesterol), and triglycerides. Simvastatin (10 mg/kg body weight/day) administered continuously from 9 days after irradiation mitigated TBI-induced increases in total- and LDL-cholesterol and triglycerides, as well as liver injury. TBI resulted in cellular peri-arterial fibrosis, whereas control hearts had less collagen and fibrosis. Simvastatin mitigated these morphological injuries. TBI resulted in cardiac mechanical dysfunction. Simvastatin mitigated cardiac mechanical dysfunction 20–120 days following TBI. To determine whether simvastatin affects the ability of the heart to withstand stress after TBI, injury from myocardial ischemia/reperfusion was determined in vitro. TBI increased the severity of an induced myocardial infarction at 20 and 80 days after irradiation. Simvastatin mitigated the severity of this myocardial infarction at 20 and 80 days following TBI. It is concluded simvastatin mitigated the increases in risk factors for cardiac disease and the extent of cardiac disease following TBI. This statin may be developed as a medical countermeasure for the mitigation of radiation-induced cardiac disease.

Strain echocardiography combined with pharmacological stress test for early detection of anthracycline induced cardiomyopathy

INTRODUCTION

Advances in echocardiography, including 2-D speckle tracking to quantitate myocardial strain and strain rate, have improved myocardial functional and mechanical evaluation and may provide a more sensitive assessment of cardiac functional and mechanical changes. Additionally, evaluating myocardial performance induced by a pharmacologic stress test (dobutamine infusion) may further improve the evaluation of potential changes in cardiac function. This study evaluates the use of 2-D speckle tracking strain echocardiography (2DSE) combined with a dobutamine stress test to detect doxorubicin induced cardiomyopathy in the rat.

METHODS

Rats were dosed once per week with 2 mg/kg doxorubicin for 6 weeks. Echocardiography was performed weekly at rest and during dobutamine infusion (20 mcg/kg/min IV).

RESULTS

Throughout the study there were no differences between control and doxorubicin treated groups at rest for radial strain, circumferential strain, fractional shortening (FS), or heart rate (HR). During dobutamine infusion, radial strain, circumferential strain, FS, and HR similarly increased significantly in both the control and doxorubicin treated groups at weeks 0, 1, and 2. At week 3 there was a significant attenuation of the increase in radial strain in the doxorubicin treated group, and at weeks 4 and 6 there was significant attenuation in radial strain and circumferential strain. No significant differences were detected in FS or HR between the two groups at any time points. Histology of the left ventricle at week 7 showed mild changes (mild cardiomyocyte vacuolation with minimal inflammation and no fibrosis) in the doxorubicin treated animals as compared to the control animals, which were consistent with mild doxorubicin induced injury.

DISCUSSION

These data suggest that 2 D speckle tracking strain echocardiography combined with dobutamine stress test can detect early changes in myocardial function and may be useful tools in early detection of drug-induced cardiac dysfunction.

A Comparison between Quantitative Gated Myocardial Perfusion Scintigraphy and Strain Echocardiography as Indicators of Ventricular Functions in Patients with Anterior Myocardial Infarction

The purpose of this study is to compare the strain echocardiographic and scintigraphic parameters for evaluating of the left ventricular (LV) functions in patients with anterior myocardial infarction (MI). Fifty-four patients (male/female: 36/18; mean age 62 ± 13 years) with anterior MI were prospectively enrolled. All patients were performed gated myocardial perfusion scintigraphy gated single-photon emission computed tomography (GSPECT) and echocardiography (EC). GSPECT data were processed and analyzed using 4D-MSPECT (4DM, Invia Medical Imaging Solutions, Ann Arbor, MI, USA). The echocardiographic strain (S) and strain rate (SR) values were calculated. The results obtained by these techniques were compared each other. A total of 918 segments of LV wall were evaluated. In all patients, 385 segments were automatically scored as normokinetic, 206 as hypokinetic, 122 as akinetic, 205 as dyskinetic and 300 as normal thickening, 348 as decrease thickening and 270 as no thickening. The means of S and SR values in thickening and motion score groups according to GSPECT were statistically different from each other (P < 0.001). There was a negative significant correlation between LV wall thickening sum score and S and SR and between LV wall motion sum score and S and SR (P < 0.001). There was a good correlation between GSPECT and echocardiographic LV-ejection fraction (r = 0.7, P < 0.001). GSPECT and strain EC are similar in quantitative grading of the severity of regional and global myocardial dysfunction in patients with anterior MI and these techniques provide valuable diagnostic information.

Magnetic resonance imaging characterization of circumferential and longitudinal strain under various coronary interventions in swine

AIM: To compare the acute changes in circumferential and longitudinal strain after exposing a coronary artery to various interventions in swine.

METHODS: Percutaneous balloon angioplasty catheter was guided to location aid device (LAD) under X-ray fluoroscopy to create different patterns of ischemic insults. Pigs (n = 32) were equally divided into 4 groups: controls, 90 min LAD occlusion/reperfusion, LAD microembolization, and combined LAD occlusion/microembolization/reperfusion. Three days after interventions, cine, tagged and viability magnetic resonance imaging (MRI) were acquired to measure and compare left and right circumferential strain, longitudinal strain and myocardial viability, respectively. Measurements were obtained using HARP and semi-automated threshold method and statistically analyzed using unpaired t-test. Myocardial and vascular damage was characterized microscopically.

RESULTS: Coronary microemboli caused greater impairment in l left ventricular (LV) circumferential strain and dyssynchrony than LAD occlusion/reperfusion despite the significant difference in the extent of myocardial damage. Microemboli also caused significant decrease in peak systolic strain rate of remote myocardium and LV dyssynchrony. Cine MRI demonstrated the interaction between LV and right ventricular (RV) at 3 d after interventions. Compensatory increase in RV free wall longitudinal strain was seen in response to all interventions. Viability MRI, histochemical staining and microscopy revealed different patterns of myocardial damage and microvascular obstruction.

CONCLUSION: Cine MRI revealed subtle changes in LV strain caused by various ischemic insults. It also demonstrated the interaction between the right and left ventricles after coronary interventions. Coronary microemboli with and without acute myocardial infarction (AMI) cause complex myocardial injury and ventricular dysfunction that is not replicated in solely AMI.

Cardiac injury after 10 gy total body irradiation: indirect role of effects on abdominal organs

The objective of this study was to determine whether radiation-induced injury to the heart after 10 Gy total body irradiation (TBI) is direct or indirect. Young male WAG/RijCmcr rats received a 10 Gy single dose using TBI, upper hemi-body (UHB) irradiation, lower hemi-body (LHB) irradiation, TBI with the kidneys shielded or LHB irradiation with the intestines shielded. Age-matched, sham-irradiated rats served as controls. The lipid profile, kidney injury, heart and liver morphology and cardiac function were determined up to 120 days after irradiation. LHB, but not UHB irradiation, increased the risk factors for cardiac disease as well as the occurrence of cardiac and kidney injury in a way that was quantitatively and qualitatively similar to that observed after TBI. Shielding of the kidneys prevented the increases in risk factors for cardiac disease. Shielding of the intestines did not prevent the increases in risk factors for cardiac disease. There was no histological evidence of liver injury 120 days after irradiation. Injury to the heart from irradiation appears to be indirect, supporting the notion that injury to abdominal organs, principally the kidneys, is responsible for the increased risk factors for and the occurrence of cardiac disease after TBI and LHB irradiation.

Xenon and isoflurane reduce left ventricular remodeling after myocardial infarction in the rat

BACKGROUND

Xenon and isoflurane are known to have cardioprotective properties. We tested the hypothesis that these anesthetics positively influence myocardial remodeling 28 days after experimental perioperative myocardial infarction and compared their effects.

METHODS

A total of 60 male Sprague-Dawley rats were subjected to 60 min of coronary artery occlusion and 120 min of reperfusion. Prior to ischemia, the animals were randomized for the different narcotic regimes (0.6 vol% isoflurane, 70 vol% xenon, or intraperitoneal injection of s-ketamine). Acute injury was quantified by echocardiography and troponin I. After 4 weeks, left ventricular function was assessed by conductance catheter to quantify hemodynamic compromise. Cardiac remodeling was characterized by quantification of dilatation, hypertrophy, fibrosis, capillary density, apoptosis, and expression of fetal genes (α/β myosin heavy chains, α-skeletal actin, periostin, and sarco/endoplasmic reticulum Ca2+-ATPase).

RESULTS

Whereas xenon and isoflurane impeded the acute effects of ischemia-reperfusion on hemodynamics and myocardial injury at a comparable level, differences were found after 4 weeks. Xenon in contrast to isoflurane or ketamine anesthetized animals demonstrated a lower remodeling index (0.7 ± 0.1 vs. 0.9 ± 0.3 and 1.0 ± 0.3g/ml), better ejection fraction (62 ± 9 vs. 49 ± 7 and 35 ± 6%), and reduced expression of β-myosin heavy chain and periostin. The effects on hypertrophy, fibrosis, capillary density, and apoptosis were comparable.

CONCLUSIONS

Compared to isoflurane and s-ketamine, xenon limited progressive adverse cardiac remodeling and contractile dysfunction 28 days after perioperative myocardial infarction.

Layer-specific strain analysis: investigation of regional deformations in a rat model of acute versus chronic myocardial infarction

Myocardial infarction (MI) injury extends from the endocardium toward the epicardium. This phenomenon should be taken into consideration in the detection of MI. To study the extent of damage at different stages of MI, we hypothesized that measurement of layer-specific strain will allow better delineation of the MI extent than total wall thickness strain at acute stages but not at chronic stages, when fibrosis and remodeling have already occurred. After baseline echocardiography scans had been obtained, 24 rats underwent occlusion of the left anterior descending coronary artery for 30 min followed by reperfusion. Thirteen rats were rescanned at 24 h post-MI and eleven rats at 2 wk post-MI. Next, rats were euthanized, and histological analysis for MI size was performed. Echocardiographic scans were postprocessed by a layer-specific speckle tracking program to measure the peak circumferential strain (S(C)(peak)) at the endocardium, midlayer, and epicardium as well as total wall thickness S(C)(peak). Linear regression for MI size versus S(C)(peak) showed that the slope was steeper for the endocardium compared with the other layers (P < 0.001), meaning that the endocardium was more sensitive to MI size than the other layers. Moreover, receiver operating characteristics analysis yielded better sensitivity and specificity in the detection of MI using endocardial S(C)(peak) instead of total wall thickness S(C)(peak) at 24 h post-MI (P < 0.05) but not 2 wk later. In conclusion, at acute stages of MI, before collagen deposition, scar tissue formation, and remodeling have occurred, damage may be nontransmural, and thus the use of endocardial S(C)(peak) is advantageous over total wall thickness S(C)(peak).

Peak longitudinal strain most accurately reflects myocardial segmental viability following acute myocardial infarction - an experimental study in open-chest pigs

Background

The extension and the transmurality of the myocardial infarction are of high predictive value for clinical outcome. The aim of the study was to characterize the ability of longitudinal, circumferential and radial strain measured by 2-dimensional speckle tracking echocardiography (2D-STE) to predict the extent of necrosis in myocardial segments following acute myocardial infarction and to separate transmural necrotic segments from non-transmural necrotic segments in a full 18-segment porcine model.

Methods

2D-STE strain was assessed in long- and short-axis following myocardial infarction in ten open-chest anesthetized pigs. Strain was defined according to systolic peak values. In segments displaying both negative and positive peaks, only the peak with the highest absolute value was utilized. Necrosis was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining and expressed as percent of each myocardial segment.

Results

Significant correlations were found between the extension of necrosis and all measured parameters of myocardial deformation (p < 0.001), but was stronger for longitudinal strain (r² = 0.52) than circumferential strain (r² = 0.38) and radial strain (r² = 0.23). The area under the receiver operator characteristic curve (AUC) for separating transmural necrotic segments (>50% necrosis) from predominantly viable segments (0–50% necrosis) was significantly larger for longitudinal strain (AUC = 0.98, CI = 0.97–1.00) when compared with circumferential strain (AUC = 0.91, CI = 0.84–0.97, p < 0.05) and radial strain (AUC = 0.90, CI = 0.83 – 0.96, p < 0.01), indicating a stronger ability of longitudinal strain to identify segments with transmural necrosis.

Conclusion

Peak strain values derived from 2D-STE correlate well with the extent of necrosis in myocardial segments following acute myocardial infarction. Longitudinal strain most accurately reflects myocardial segmental viability in this setting.

Mitochondrial DNA variant for complex I reveals a role in diabetic cardiac remodeling

Myocardial remodeling and dysfunction are serious complications of type 2 diabetes mellitus (T2DM). Factors controlling their development are not well established. To specifically address the role of the mitochondrial genome, we developed novel conplastic rat strains, i.e. strains with the same nuclear genome but a different mitochondrial genome. The new animals were named T2DN(mtFHH) and T2DN(mtWistar), where the acronym T2DN denotes their common nuclear genome (type 2 diabetic nephropathy (T2DN) rats) and mtFHH or mtWistar the origin of their mitochondria, Fawn Hooded Hypertensive (FHH) or Wistar rats, respectively. The T2DN(mtFHH) and T2DN(mtWistar) showed a similar progression of diabetes as determined by HbA1c, cholesterol, and triglycerides with normal blood pressure, thus enabling investigation of the specific role of the mitochondrial genome in cardiac function without the confounding effects of obesity or hypertension found in other models of diabetes. Echocardiographic analysis of 12-week-old animals showed no abnormalities, but at 12 months of age the T2DN(mtFHH) showed left ventricular remodeling that was verified by histology. Decreased complex I and complex IV but not complex II activity within the electron transport chain was found only in T2DN(mtFHH), which was not explained by differences in protein content. Decreased cardiac ATP levels in T2DN(mtFHH) were in agreement with a lower ATP synthetic capacity by isolated mitochondria. Together, our data provide experimental evidence that mtDNA sequence variations have an additional role in energetic heart deficiency. The mitochondrial DNA background may explain the increased susceptibility of certain T2DM patients to develop myocardial dysfunction.

Value of segmental myocardial strain by 2-dimensional strain echocardiography for assessment of scar area induced in a rat model of myocardial infarction

OBJECTIVES

Two-dimensional strain echocardiography (2DSE) technique has enabled accurate quantification of regional myocardial function. This experimental study was aimed to investigate the value of 2DSE in detection of segmental regional myocardial dysfunction induced by fibrosis following myocardial infarction in a small animal (rat) model.

METHODS

A rat model of myocardial infarction was established by ligation of the proximal left anterior descending coronary artery in 17 SD rats. Regional myocardial function was detected by 2DSE at baseline and 4-weeks post-infarction, including end-systolic radial strain and strain rate (SR and SrR) and end-systolic circumferential strain and strain rate (SC and SrC) of each of six segments at papillary level. According to the size of scar found by histologic Masson staining, the optimal cutoff points of parameters for detecting scar area were analyzed and the sensitivity and specificity of every parameter to detect myocardial scar were obtained using ROC.

RESULTS

(1) Comparing with parameters measured at baseline, there were significant decreases in SR, SrR, SC and SrC of each segment at 4 weeks post-infarction, with the worst in the infarct area (32.90 ± 8.79 vs 11.18 ± 3.89, 6.28 ± 1.35 vs 3.18 ± 0.47, -14.46 ± 2.21 vs -6.30 ± 2.17 and 4.93 ± 0.95 vs 2.59 ± 1.16, respectively) (all P < 0.05). (2)By 4 weeks, the myocardium of infarct area (anteroseptum, anterior and anterolateral) had fibrosis (31.33 ± 9.89, 73.42 ± 13.21 and 13.99 ± 3.24%, respectively) with minimal fibrosis in inferoseptal segment (0.32 ± 0.19%), no fibrosis was found in the inferior and inferolateral segments. (3)Significant negative correlations were found between the size of segmental scar and 2DSE parameters (r-value -0.61 ~ -0.80, all P < 0.01) with the strongest correlation in SR. SR less than 10% has 84% sensitivity and 98% specificity for detecting segments of scar area greater than 30% with AUC = 0.97.

CONCLUSIONS

2DSE is able to assess regional myocardial dysfunction in a rat model of myocardial infarction and has high accuracy in detecting infarct segments with scar area greater than 30%.

Two-dimensional strain combined with adenosine stress echocardiography assessment of viable myocardium

The objective of this study was to explore a new method for the identification of viable myocardium by means of two-dimensional (2D) strain imaging combined with adenosine stress echocardiography. A total of 15 anesthetized open-chest healthy mongrel dogs underwent left anterior descending coronary artery occlusion for 90 min followed by 120-min reperfusion. Adenosine was infused at 140 μg kg(-1) min(-1) over a period of 6 min. Images were acquired at baseline (when pericardial cradle was made), after reperfusion (when reperfusion finished) and after adenosine administration (while administration stopped). Measurements of the regional peak-systolic strain in radial, circumferential, and longitudinal motion on anterior wall and anterior septum were, respectively, performed under different conditions. The dogs were killed after the echocardiographic studies finished and then the area of infracted myocardium was defined by triphenyltetrazolium chloride histology. A segment with equal or less than 50% area of infracted myocardium was considered to be viable. As a result, 37 regions were viable whereas 53 were non-viable among 90 regions in 15 dogs. At baseline, there was no significant difference in peak-systolic radial strain (Rs), circumferential strain (Cs), and longitudinal strain (Ls) between the viable and non-viable groups. After reperfusion, Rs, Cs, and Ls in absolute value decreased compared to those at baseline in both groups, although there was no significant difference between these groups. Rs and Ls increased after adenosine administration compared to reperfusion (p < 0.01; p < 0.05) in viable group while there were no changes in non-viable group. Compared with non-viable group Rs, Cs and Ls in viable group increased significantly (p < 0.01; 0.05) after adenosine administration. There was a negative correlation between Rs and infarct size (r = -0.72). Cs and Ls correlated well with infarct size, respectively (r = 0.40; 0.67). A change of Rs more than 13.5% has a sensitivity of 83.8% and a specificity of 83.0% for viable whereas a change of Ls more than 11% allowed a sensitivity of 78.4% and a specificity of 88.7%. Combined with these two variables, the sensitivity and specificity could reach 91.9 and 79.2%. Two-dimensional strain imaging combined with adenosine stress echocardiography can provide a new way to distinguish viable myocardium from the non-viable.

Left ventricular strain and strain rate echocardiography analysis in patients with total and subtotal occlusion in the infarct-related left anterior descending artery

BACKGROUND

Numerous studies show that percutaneous coronary intervention has no clinical benefit in patients with total occlusion. Both regional and global left ventricle (LV) functions may be evaluated in detail by strain (S) and strain rate (SR) echocardiography. The purpose of this study is to evaluate whether S and SR echocardiography may be used to determine the total occlusion.

METHOD

Sixty stable patients who have total or subtotal occlusion in the infarct-related left anterior descending artery were enrolled (Total occlusion group: 35 and subtotal occlusion group: 25 patients). In all patients, LV longitudinal S and SR data were obtained from total 14 segments.

RESULTS

S values of middle and apical segments of LV were significantly lower in the total occlusion groups. In SR analysis, middle and apical values of all walls were significantly different between the groups. The total SR of the middle and apical segments was significantly lower in the total occlusion group (respectively, total SR in middle segments: -3.4 ± 0.8% vs. -4.6 ± 1.0%, P < 0.00001 and total SR in apical segments: -1.7 ± 0.5% vs. -2.8 ± 0.6%, P = 0.001). The total SR values of four walls were also significantly lower in the total occlusion group (-10.3 ± 2.0% vs. -13 ± 3.1%, P < 0.0001). For predicting total occlusion, the highest sensitivity levels (84%) were obtained in SR of middle-anterior segment. SR of middle-septum and middle-lateral segments has the highest specificity levels (86%).

CONCLUSION

Total occlusion in stable patients with acute coronary syndrome has an unfavorable effect on the LV regional and global functions. Patients with total occlusion may be identified by S and SR echocardiography.

Speckle tracking imaging improves in vivo assessment of EPO-induced myocardial salvage early after ischemia-reperfusion in rats

A noninvasive assessment of infarct size and transmural extension of myocardial infarction (TEMI) is fundamental in experimental models of ischemia-reperfusion. Conventional echocardiography parameters are limited in this purpose. This study was designed to examine whether speckle tracking imaging can be used in a rat model of ischemia-reperfusion to accurately detect the reduction of infarct size and TEMI induced by erythropoietin (EPO) as early as 24 h after reperfusion. Rats were randomly assigned to one of three groups: myocardial infarction (MI)-control group, 45 min ischemia followed by 24 h of reperfusion; MI-EPO group, similar surgery with a single bolus of EPO administered at the onset of reperfusion; and sham-operated group. Short-axis two-dimensional echocardiography was performed after reperfusion. Global radial (GSr) and circumferential (GScir) strains were compared with infarct size and TEMI assessed after triphenyltetrazolium chloride staining. As a result, ejection fraction, shortening fraction, GSr, and GScir significantly correlated to infarct size, whereas only GSr and GScir significantly correlated to TEMI. EPO significantly decreased infarct size (30.8 ± 3.5 vs. 56.2 ± 5.7% in MI-control, P < 0.001) and TEMI (0.37 ± 0.05 vs. 0.77 ± 0.05 in MI-control, P < 0.001). None of the conventional echocardiography parameters was significantly different between the MI-EPO and MI-control groups, whereas GSr was significantly higher in the MI-EPO group (29.1 ± 4.7 vs. 16.4 ± 3.3% in MI-control; P < 0.05). Furthermore, GScir and GSr appeared to be the best parameters to identify a TEMI >0.75 24 h after reperfusion. In conclusion, these findings demonstrate the usefulness of speckle tracking imaging in the early evaluation of a cardioprotective strategy in a rat model of ischemia-reperfusion.

10 Gy total body irradiation increases risk of coronary sclerosis, degeneration of heart structure and function in a rat model

PURPOSE

To determine the impact of 10 Gy total body irradiation (TBI) or local thorax irradiation, a dose relevant to a radiological terrorist threat, on lipid and liver profile, coronary microvasculature and ventricular function.

MATERIALS AND METHODS

WAG/RijCmcr rats received 10 Gy TBI followed by bone marrow transplantation, or 10 Gy local thorax irradiation. Age-matched, non-irradiated rats served as controls. The lipid profile and liver enzymes, coronary vessel morphology, nitric oxide synthase (NOS) isoforms, protease activated receptor (PAR)-1 expression and fibrinogen levels were compared. Two-dimensional strain echocardiography assessed global radial and circumferential strain on the heart.

RESULTS

TBI resulted in a sustained increase in total and low density lipoprotein (LDL) cholesterol (190 +/- 8 vs. 58 +/- 6; 82 +/- 8 vs. 13 +/- 3 mg/dl, respectively). The density of small coronary arterioles was decreased by 32%. Histology revealed complete blockage of some vessels while cardiomyocytes remained normal. TBI resulted in cellular peri-arterial fibrosis whereas control hearts had symmetrical penetrating vessels with less collagen and fibroblasts. TBI resulted in a 32 +/- 4% and 28 +/- 3% decrease in endothelial NOS and inducible NOS protein, respectively, and a 21 +/- 4% and 35 +/- 5% increase in fibrinogen and PAR-1 protein respectively, after 120 days. TBI reduced radial strain (19 +/- 8 vs. 46 +/- 7%) and circumferential strain (-8 +/- 3 vs. -15 +/- 3%) compared to controls. Thorax-only irradiation produced no changes over the same time frame.

CONCLUSIONS

TBI with 10 Gy, a dose relevant to radiological terrorist threats, worsened lipid profile, injured coronary microvasculature, altered endothelial physiology and myocardial mechanics. These changes were not manifest with local thorax irradiation. Non-thoracic circulating factors may be promoting radiation-induced injury to the heart.

A New Tool for Automatic Assessment of Segmental Wall Motion Based on Longitudinal 2D Strain

Background— Identification and quantification of segmental left ventricular wall motion abnormalities on echocardiograms is of paramount clinical importance but is still performed by a subjective visual method. We constructed an automatic tool for assessment of wall motion based on longitudinal strain.

Methods and Results— Echocardiograms of 105 patients (3 apical views) were blindly analyzed by 12 experienced readers. Visual segmental scores (VSS) and peak systolic longitudinal strain were assigned to each of 18 segments per patient. Ranges of peak systolic longitudinal strain that best fit VSS (by receiver operating characteristic analysis) were used to generate automatic segmental scores (ASS). Comparisons of ASS and VSS were performed on 1952 analyzable segments. There was agreement of wall motion scores between both methods in 89.6% of normal, 39.5% of hypokinetic, and 69.4% of akinetic segments. Correlation between methods was r =0.63 ( P <0.0001). Interobserver and intraobserver reliability using interclass correlation for scoring segmental wall motion into 3 scores by ASS was 0.82 and 0.83 and by VSS 0.70 and 0.69, respectively. Compared with VSS (majority rule), ASS had a sensitivity, specificity, and accuracy of 87%, 85%, and 86%, respectively. ASS and VSS had similar success rates for correct identification of wall motion abnormalities in territories supplied by culprit arteries. VSS had greater specificity and positive predictive values, whereas ASS had higher sensitivity and negative predictive values for identifying the culprit artery.

Conclusions— Automatic quantification of wall motion on echocardiograms by this tool performs as well as visual analysis by experienced echocardiographers, with a greater reliability and similar agreement to angiographic findings.

Usefulness of two-dimensional strain echocardiography to predict segmental viability following acute myocardial infarction and optimization using bayesian logistic spatial modeling

Viability assessment after acute myocardial infarction (MI) is important to guide revascularization. Two-dimensional strain echocardiography was shown to predict viability, but the method assumed that strain in each segment is independent of contiguous segments. The aim of this study was to test the hypotheses that segmental strain after MI is spatially correlated and that using a Bayesian approach improves the prediction of nonviable myocardium. Twenty-one subjects (mean age 58 +/- 12 years, 6 women) with MI >or=2 weeks before recruitment underwent 2-dimensional strain echocardiography and late gadolinium enhancement (LGE) cardiac magnetic resonance imaging within 48 hours of each other. The heart was divided into 16 segments, and longitudinal, radial, and circumferential strains were measured using software. Using similar segmentation, LGE was measured, and segments with >50% LGE were considered nonviable. Spearman's analyses were used to assess the spatial correlation of strain, and receiver-operating characteristic curve analysis was used to determine the prediction of nonviable myocardium without and with a Bayesian logistic spatial conditionally autoregressive (CAR) model. There was a significant spatial correlation in strain and LGE among segments, especially in the apex. Longitudinal strain was the best predictor of nonviability and was impaired in nonviable myocardium (-12.1 +/- 0.6%, -8.0 +/- 0.6%, and -4.6 +/- 1% for 0%, 1% to 50%, and >50% LGE, respectively, p <0.001). Use of the CAR model improved the area under the curve for the detection of nonviable myocardium (from 0.7 to 0.94). A CAR probabilistic score of 0.17 had 88% sensitivity and 86% specificity for detecting nonviable myocardium. In conclusion, longitudinal strain from 2-dimensional strain echocardiography can predict myocardial viability after MI, and exploiting spatial correlations in segmental strain using Bayesian CAR modeling enhances the ability of 2-dimensional strain to predict nonviable myocardium.

Two-dimensional strain imaging of controlled rabbit hearts

Ultrasound strain imaging using 2-D speckle tracking has been proposed to quantitatively assess changes in myocardial contractility caused by ischemia. Its performance must be demonstrated in a controlled model system as a step toward routine clinical application. In this study, a well-controlled 2-D cardiac elasticity imaging technique was developed using two coplanar and orthogonal linear probes simultaneously imaging an isolated retroperfused rabbit heart. Acute ischemia was generated by left anterior descending (LAD) artery ligation. An excitation-contraction decoupler, 2,3-butanedione monoxime, was applied at a 4-mM concentration to reversibly reduce myocardial contractility. Results using a single probe demonstrate that directional changes in the in-plane principal deformation axes can help locate the bulging area as a result of LAD ligation, which matched well with corresponding Evans Blue staining, and strains or strain magnitude, based on principal stretches, can characterize heart muscle contractility. These two findings using asymmetric displacement accuracy (i.e., normal single-probe measurements with good axial but poor lateral estimates) were further validated using symmetric displacement accuracy (i.e., dual-probe measurements using only accurate axial tracking estimates from each). However, the accuracy of 2-D cardiac strain imaging using a single probe depends on the probe's orientation because of the large variance in lateral displacement estimates.

Validation of echocardiographic two-dimensional speckle tracking longitudinal strain imaging for viability assessment in patients with chronic ischemic left ventricular dysfunction and comparison with contrast-enhanced magnetic resonance imaging

The purpose of the present study was to compare longitudinal strain assessed by two-dimensional speckle tracking with scar tissue on contrast-enhanced magnetic resonance imaging (MRI) in patients with chronic ischemic left ventricular (LV) dysfunction. The aim was also to define a cutoff value for regional strain to discriminate between viable myocardium and transmural scar. Ninety patients with chronic ischemic LV dysfunction underwent transthoracic echocardiography to measure global and segmental (regional) longitudinal LV strain using two-dimensional speckle tracking and cine MRI followed by contrast-enhanced MRI to assess segmental LV function and the segmental/global (transmural) extent of scar tissue. The optimal cutoff value for regional strain to discriminate between segments with viable myocardium and segments with transmural scar was also determined. A good correlation was found between global LV strain and the global extent of scar tissue on contrast-enhanced MRI (R = 0.62, p <0.001). The mean segmental strain in segments without scar tissue was -10.4% +/- 5.2% compared with 0.6% +/- 4.9% in segments with transmural scar tissue (p <0.001). A strain value of -4.5% discriminated between segments with viable myocardium and segments with transmural scar tissue on contrast-enhanced MRI with a sensitivity of 81.2% and specificity of 81.6%. In conclusion, global and regional longitudinal strain measured with two-dimensional speckle tracking is associated with the global and regional (transmural) extent of scar tissue on contrast-enhanced MRI. A cutoff value of -4.5% for regional strain discriminated between segments with viable myocardium and those with transmural scar tissue on contrast-enhanced MRI with a sensitivity of 81.2% and specificity of 81.6%.

Non-Doppler two dimensional strain imaging for evaluation of coronary artery disease

Over the recent years, strain echocardiography has emerged as a quantitative technique for the evaluation of global and segmental cardiac function. Strain is a measure of deformation, expressed as a percent change in a segment's length compared to its predeformation length. Strain rate (SR) is the local rate of deformation or strain per unit time. Recently non-Doppler two dimensional strain imaging has been developed. This technique is based on tracking ultrasonic speckles from the two dimensional echocardiographic images. These speckles are followed over a number of successive frames, and myocardial velocity is calculated by measuring frame-to-frame changes. This technique is independent of the Doppler angle of incidence and allows measurement of several vectors of strain within myocardial tissue. Non-Doppler strain is a powerful tool, enabling detection of subtle abnormalities in myocardial function. Current evidence shows that non-Doppler strain imaging may allow identification of the early changes that occur with ischemic insult to the myocardium. It may also provide a tool for identification of scarred, non-viable myocardium, with similar accuracy to that of cardiac MRI. Non-Doppler strain imaging is likely to become a standard tool in the evaluation of patients with ischemic heart disease.

Phase rotation methods in filtering correlation coefficients for ultrasound speckle tracking

In speckle-tracking-based myocardial strain imaging, large interframe/volume peak-systolic strains cause peak hopping artifacts separating the highest correlation coefficient peak from the true peak. A correlation coefficient filter was previously designed to minimize peak hopping artifacts. For large strains, however, the correlation coefficient filter must follow the strain distribution to remove peak hopping effectively. This processing usually means interpolation and high computational load. To reduce the computational burden, a narrow band approximation using phase rotation is developed in this paper to facilitate correlation coefficient filtering. Correlation coefficients are first phase rotated to increase coherence, then filtered. Rotated phase angles are determined by the local strain and spatial position. This form of correlation coefficient filtering enhances true correlation coefficient peaks in large strain applications if decorrelation due to deformation does not completely destroy the coherence among neighboring correlation coefficients. The assumed strain used in the filter can also deviate from the true strain and still be effective. Further improvement in displacement estimation can be expected by combining correlation coefficient filtering with a new Viterbi-based displacement estimator.

Reduced peak-hopping artifacts in ultrasonic strain estimation using the Viterbi algorithm

Internal strain resulting from tissue deformation can be estimated by correlation processing of speckle patterns within complex (i.e., radio frequency) ultrasound images acquired during deformation. At large deformations, the magnitude of the correlation coefficient peak can be significantly lower than unity, so that random speckle correlations will exceed the true peak. This effect is called "peak hopping" and causes significant errors in displacement and deformation estimates. Here we investigate the Viterbi algorithm, a dynamic programming procedure, to overcome peak-hopping artifacts by finding the most likely sequence of hidden states in a sequence of observed events. It is well suited to motion estimation in elasticity-imaging studies because adjacent tissue elements remain adjacent following deformation. Particularly, tissue elements along an ultrasonic beam in one image lie along a 3-D continuous curve in the next image instant. The observed event in this case is the correlation coefficient of a pixel at a certain displacement. Radio-frequency data were generated before and after deformation with an average strain of 6%. Simulations were performed for a homogenous medium and for a medium with a stiffer inclusion. Results show that Viterbi processing of speckle-tracking outputs can significantly reduce peak-hopping artifacts.

Relation of immediate decrease in ventricular septal strain after alcohol septal ablation for obstructive hypertrophic cardiomyopathy to long-term reduction in left ventricular outflow tract pressure gradient

Alcohol septal ablation (ASA) aims to decrease left ventricular outflow tract (LVOT) obstruction in patients with obstructive hypertrophic cardiomyopathy (HC). To date, no diagnostic variables at baseline are available to predict long-term success of the procedure. We hypothesized that an immediate decrease in septal longitudinal strain after ASA would be associated with sustained LVOT gradient decrease after 6 months. ASA was performed in 22 patients with HC and severe drug-refractory symptoms. Clinical evaluation and 2-dimensional echocardiography were performed before, 1 day after, and 6 months after ASA. During 6-month follow-up, New York Heart Association class improved (2.7 +/- 0.5 vs 1.4 +/- 0.6, p <0.01) and LVOT gradient decreased (68 +/- 31 vs 21 +/- 21 mm Hg, p <0.01). Strain evaluation showed considerable decreases in basal septal strain (-12 +/- 3% vs -8 +/- 2%, p <0.01) and midseptal strain (-13 +/- 4% vs -8 +/- 3%, p <0.01) 1 day after ASA. Decreases in basal septal and midseptal strain 1 day after ASA were strongly related to the decrease in LVOT gradient during 6-month follow-up (r = 0.70, p <0.01, and r = 0.65, p <0.01, respectively). In conclusion, in patients with HC and severe drug-refractory symptoms, immediate decrease in septal strain after ASA is strongly related to a decrease in LVOT gradient after 6 months and might therefore serve as an early determinant for long-term success of the ASA procedure.

Sepiapterin decreases acute rejection and apoptosis in cardiac transplants independently of changes in nitric oxide and inducible nitric-oxide synthase dimerization

Tetrahydrobiopterin (BH(4)), a cofactor of inducible nitric-oxide synthase (iNOS), is an important post-translational regulator of NO bioactivity. We examined whether treatment of cardiac allograft recipients with sepiapterin [S-(-)-2-amino-7,8-dihydro-6-(2-hydroxy-1-oxopropyl)-4-(1H)-pteridinone], a precursor of BH(4), inhibited acute rejection and apoptosis in cardiac transplants. Heterotopic cardiac transplantation was performed in Wistar-Furth donor to Lewis recipient strain rats. Recipients were treated daily after transplantation with 10 mg/kg sepiapterin. Grafts were harvested on post-transplant day 6 for analysis of BH(4) (high-performance liquid chromatography), expression of inflammatory cytokines (reverse transcription- and real-time polymerase chain reaction), iNOS (Western blots), and NO (Griess reaction and NO analyzer). Histological rejection grade was scored, and graft function was determined by echocardiography. Apoptosis, protein nitration, and oxidative stress were determined by immunohistochemistry. Treatment of allografts with sepiapterin increased cardiac BH(4) levels by 3-fold without changing protein levels of GTP cyclohydrolase, the enzyme that regulates de novo BH(4) synthesis. Sepiapterin decreased inflammatory cell infiltrate and significantly inhibited histological rejection scores and apoptosis similar in magnitude to cyclosporine. Sepiapterin also decreased nitrative and oxidative stress. Sepiapterin caused a smaller increase in left ventricular mass versus untreated allografts but without improving fractional shortening. Sepiapterin did not alter tumor necrosis factor-alpha and interferon-gamma expression, whereas it decreased interleukin (IL)-2 expression. Sepiapterin did not change total iNOS protein or monomer levels, or plasma and tissue NO metabolites levels. It is concluded that the mechanism(s) of antirejection are due in part to decreased apoptosis, protein nitration, and oxidation of cardiomyocytes, which seems to be mediated at the immune level by limiting inflammatory cell infiltration via decreased IL-2-mediated T-lymphocyte expansion.

Strain and strain rate imaging by echocardiography - basic concepts and clinical applicability

Echocardiographic strain and strain-rate imaging (deformation imaging) is a new non-invasive method for assessment of myocardial function. Due to its ability to differentiate between active and passive movement of myocardial segments, to quantify intraventricular dyssynchrony and to evaluate components of myocardial function, such as longitudinal myocardial shortening, that are not visually assessable, it allows comprehensive assessment of myocardial function and the spectrum of potential clinical applications is very wide. The high sensitivity of both tissue Doppler imaging (TDI) derived and two dimensional (2D) speckle tracking derived myocardial deformation (strain and strain rate) data for the early detection of myocardial dysfunction recommend these new non-invasive diagnostic methods for extensive clinical use. In addition to early detection and quantification of myocardial dysfunction of different etiologies, assessment of myocardial viability, detection of acute allograft rejection and early detection of allograft vasculopathy after heart transplantation, strain and strain rate data are helpful for therapeutic decisions and also useful for follow-up evaluations of therapeutic results in cardiology and cardiac surgery. Strain and strain rate data also provide valuable prognostic information, especially prediction of future reverse remodelling after left ventricular restoration surgery or after cardiac resynchronization therapy and prediction of short and median-term outcome without transplantation or ventricular assist device implantation of patients referred for heart transplantation.The Review explains the fundamental concepts of deformation imaging, describes in a comparative manner the two major deformation imaging methods (TDI-derived and speckle tracking 2D-strain derived) and discusses the clinical applicability of these new echocardiographic tools, which recently have become a subject of great interest for clinicians.

Myocardial dysfunction in the periinfarct and remote regions following anterior infarction in rats quantified by 2D radial strain echocardiography: an observational cohort study

Background

Heart failure from adverse ventricular remodeling follows myocardial infarction, but the contribution of periinfarct and remote myocardium to the development of cardiomyopathy remains poorly defined. 2D strain echocardiography (2DSE) is a novel and sensitive tool to measure regional myocardial mechanics. The aim is to quantify radial strain in infarcted (I), periinfarct (PI) and remote (R) myocardial regions acutely and chronically following anterior infarction in rats.

Methods

The left anterior coronary artery of male Sprague-Dawley rats (270–370 g) were occluded for 20–30 minutes and 2DSE was performed in the acute setting (n = 10; baseline and 60 minutes post-reperfusion) and in the chronic setting (n = 14; baseline, 1, 3 and 6 weeks). Using software, radial strain was measured in the mid-ventricle in short axis view. The ventricle was divided into 3 regions: I (anteroseptum, anterior and anterolateral), PI – (inferoseptum and inferolateral) and R – (inferior). Infarct size was measured using triphenyl tetrazolium chloride in the acute group.

Results

Following infarct, adverse remodeling occurred with progressive increase in left ventricular size, mass and reduced fractional shortening within 6 weeks. Radial strain decreased not only in the infarct but also in the periinfarct and remote regions acutely and chronically (I, PI, R, change vs. baseline, 60 minutes -32.7 ± 8.7, -17.4 ± 9.4, -13.5 ± 11.6%; 6 weeks -24.4 ± 8.2, -17.7 ± 8.3, -15.2 ± 8.4% respectively, all p < 0.05). Reduced radial strain in periinfarct and remote regions occurred despite minimal or absent necrosis (area of necrosis I, PI, R: 48.8 ± 23, 5.1 ± 6.6, 0 ± 0%, p < 0.001 vs. I).

Conclusion

Following left anterior coronary occlusion, radial strain decreased at 60 minutes and up to 6 weeks in the periinfarct and remote regions, similar to the reduction in the infarct region. This demonstrates early and chronic myopathic process in periinfarct and remote regions following myocardial infarction that may be an under recognized but important contributor to adverse left ventricular remodeling and progression to ischemic cardiomyopathy.