Ultrafast Myocardial Principal Strain Ultrasound Elastography During Stress Tests: In Vitro Validation and In Vivo Feasibility

Objective myocardial contractility assessment during stress tests aims to improve the diagnosis of myocardial ischemia. Tissue Doppler imaging (TDI) or optical flow (OF) speckle tracking echocardiography (STE) has been used to quantify myocardial contractility at rest. However, this is more challenging during stress tests due to image decorrelation at high heart rates. Moreover, stress tests imply a high frame rate which leads to a limited lateral field of view. Therefore, a large lateral field-of-view robust ultrafast myocardial regularized OF-TDI principal strain estimator has been developed for high-frame-rate echocardiography of coherently compounded transmitted diverging waves. The feasibility and accuracy of the proposed estimator were validated in vitro (using sonomicrometry as the gold standard) and in vivo stress experiments. Compared with OF strain imaging, the proposed estimator improved the accuracy of principal major and minor strains during stress tests, with an average contrast-to-noise ratio improvement of 4.4 ± 2.7 dB ( p -value < 0.01). Moreover, there was a significant correlation and a very close agreement between the proposed estimator and sonomicrometry for tested heart rates between 60 and 180 beats per minute (bpm). The averages ± standard deviations (STD) of R² and biases ± STD between them were 0.96 ± 0.04 ( p -value < 0.01) and 0.01 ± 0.03% in the axial direction, respectively; and 0.94 ± 0.02 ( p -value < 0.01) and 0.04 ± 0.06% in the lateral direction, respectively. These results suggest that the proposed estimator could be useful clinically to provide an accurate and quantitative 2-D large lateral field-of-view myocardial strain assessment at high heart rates during stress echocardiography.

Segmental strain analysis for the detection of chronic ischemic scars in non-contrast cardiac MRI cine images

Cardiac magnetic resonance imaging (MRI) with late gadolinium enhancement (LGE) is considered the gold standard for scar detection after myocardial infarction. In times of increasing skepticism about gadolinium depositions in brain tissue and contraindications of gadolinium administration in some patient groups, tissue strain-based techniques for detecting ischemic scars should be further developed as part of clinical protocols. Therefore, the objective of the present work was to investigate whether segmental strain is noticeably affected in chronic infarcts and thus can be potentially used for infarct detection based on routinely acquired non-contrast cine images in patients with known coronary artery disease (CAD). Forty-six patients with known CAD and chronic scars in LGE images (5 female, mean age 52 ± 19 years) and 24 gender- and age-matched controls with normal cardiac MRI (2 female, mean age 47 ± 13 years) were retrospectively enrolled. Global (global peak circumferential [GPCS], global peak longitudinal [GPLS], global peak radial strain [GPRS]) and segmental (segmental peak circumferential [SPCS], segmental peak longitudinal [SPLS], segmental peak radial strain [SPRS]) strain parameters were calculated from standard non-contrast balanced SSFP cine sequences using commercially available software (Segment CMR, Medviso, Sweden). Visual wall motion assessment of short axis cine images as well as segmental circumferential strain calculations (endo-/epicardially contoured short axis cine and resulting polar plot strain map) of every patient and control were presented in random order to two independent blinded readers, which should localize potentially infarcted segments in those datasets blinded to LGE images and patient information. Global strain values were impaired in patients compared to controls (GPCS p = 0.02; GPLS p = 0.04; GPRS p = 0.01). Patients with preserved ejection fraction showed also impeded GPCS compared to healthy individuals (p = 0.04). In patients, mean SPCS was significantly impaired in subendocardially (-  5.4% ± 2) and in transmurally infarcted segments (- 1.2% ± 3) compared to remote myocardium (- 12.9% ± 3, p = 0.02 and 0.03, respectively). ROC analysis revealed an optimal cut-off value for SPCS for discriminating infarcted from remote myocardium of - 7.2% with a sensitivity of 89.4% and specificity of 85.7%. Mean SPRS was impeded in transmurally infarcted segments (15.9% ± 6) compared to SPRS of remote myocardium (31.4% ± 5; p = 0.02). The optimal cut-off value for SPRS for discriminating scar tissue from remote myocardium was 16.6% with a sensitivity of 83.3% and specificity of 76.5%. 80.3% of all in LGE infarcted segments (118/147) were correctly localized in segmental circumferential strain calculations based on non-contrast cine images compared to 53.7% (79/147) of infarcted segments detected by visual wall motion assessment (p > 0.01). Global strain parameters are impaired in patients with chronic infarcts compared to controls. Mean SPCS and SPRS in scar tissue is impeded compared to remote myocardium in infarcts patients. Blinded to LGE images, two readers correctly localized 80% of infarcted segments in segmental circumferential strain calculations based on non-contrast cine images, in contrast to only 54% of infarcted segments detected due to wall motion abnormalities in visual wall motion assessment. Analysis of segmental circumferential strain shows a promising method for detection of chronic scars in routinely acquired, non-contrast cine images for patients who cannot receive or decline gadolinium.

Left ventricular diastolic dysfunction is associated with cerebral infarction in young hypertensive patients: A retrospective case-control study

Studies have indicated that hypertension is associated with the occurrence of acute cerebral infarction (CI) in young patients (18-45 years). However, the association between CI and left ventricular diastolic (LVD) dysfunction in young patients with hypertension has rarely been reported. The purpose of the present study was to investigate the association between LVD dysfunction and acute CI in young patients with hypertension. A total of 92 patients with acute CI who had hypertension were selected as the study group (CI group) and 98 young patients with only hypertension were selected as the control group (non-CI group). Blood pressure measurements, LVD functional assessment and cerebral MRI were performed. The χ² test was used to compare the left ventricular diastolic function between the CI and non-CI groups. The results indicated that LVD function of young patients was associated with hypertension and there was a correlation between the decrease in LVD function and the occurrence of acute CI in young patients with hypertension. The incidence of acute CI was higher in patients with decreased LVD function than in those with normal LVD function. In conclusion, hypertension in the young is associated with decreased LVD function and is a risk factor for diastolic dysfunction of the left ventricle. LVD function may be an independent predictor of acute CI in young patients with hypertension and should be considered by clinicians. By predicting the risk of acute CI in young patients with hypertension, LVD testing may aid in the primary prevention of CI or guide early treatment.

Impact of Right Ventricular Geometry and Left Ventricular Hypertrophy on Right Ventricular Mechanics and Clinical Outcomes in Hypoplastic Left Heart Syndrome

BACKGROUND

Right ventricular (RV) function is a major determinant of survival in hypoplastic left heart syndrome (HLHS). However, the relation of RV geometry to myocardial mechanics and their relation to transplant-free survival are incompletely characterized.

METHODS

We retrospectively studied 48 HLHS patients from the Hospital for Sick Children, Toronto, (median age, 2.2; interquartile range, 3.62 years) at different surgical stages. Patients were grouped by the presence (n = 23) or absence (n = 25) of RV "apical bulging" defined as a sigmoid-shaped septum with the RV leftward apical segment contiguous with the left ventricular (LV) lateral wall. Regional and global RV strain were measured using speckle-tracking echocardiography, and regional strains were analyzed for patterns and peak values. These were compared between HLHS anatomical subtypes and between patients with versus without apical bulging. We further investigated the association between RV geometry and dysfunction with the outcomes of heart failure, death, or transplant.

RESULTS

RV global (-7.3% ± 2.8% vs -11.2% ± 4.4%; P = .001), basal septal (-3.8% ± 3.2% vs -11.4% ± 5.8%; P = .0001) and apicolateral (-5.1% ± 3.5% vs -8.0% ± 5.8%, P = .001) longitudinal strain were lower in patients with versus without apical bulging, respectively. Apical bulging was equally prevalent in all HLHS anatomical variants. Twenty of 22 (91%) patients with apical bulging displayed hypertrophy of the LV apical and lateral segments. Death or transplantation were approximately equal in both groups but related to reduced RV global strain in patients with (seven of seven) and not in those without apical bulging (two of eight; P = .022).

CONCLUSIONS

These results suggest that the finding of apical bulging is related to the presence of a hypertrophied hypoplastic LV, with a negative impact on regional and global RV function. Therefore, analysis of RV and LV geometry and mechanics may aid in the assessment and prognostication of this high-risk population.

Role of viability imaging in the post-STICH era

PURPOSE OF REVIEW

Recent results from prospective randomized controlled trials examining the management of patients with ischemic cardiomyopathy (ICM) have questioned both the added value of revascularization over contemporary optimal medical therapy (OMT) and the use of viability testing as a gate-keeper to revascularization. The purpose of this review is to summarize recent trial evidence before discussing future perspectives in the field.

RECENT FINDINGS

The Surgical Treatment of Ischemic Heart Failure (STICH) trial, PPAR-2 trial and Heart Failure Revascularisation Trial have all reported their results within the past 5 years. None of these trials found revascularization superior to OMT in improving survival of ICM patients. Additionally, the STICH trial's viability substudy suggested that pretreatment viability testing was not beneficial.

SUMMARY

ICM patients remain a clinical conundrum. The numerous limitations of the recent RCTs have led to uncertainty about optimal management. Revascularization continues to be offered to patients with evidence of myocardial viability. Further studies are required to answer the outstanding questions in the management of patients with ICM.

Effect of coronary artery bypass surgery on left ventricular function as assessed by strain and strain rate imaging

INTRODUCTION

This study examined the effect of coronary artery revascularization on left ventricular function and the results of strain imaging for the detection of ischemia before and after coronary artery bypass graft (CABG) surgery.

MATERIAL AND METHODS

Sixty-eight patients with a history of coronary artery disease (CAD) were included, prospectively. Conventional echocardiography and color tissue Doppler-derived strain-strain rate echocardiographic imaging were performed 24 hours before and 3 months after CABG surgery.

RESULTS

While strain rate values of the basal septum, middle segment of the lateral wall, middle segment of the inferior wall, and middle and basal segments of the anterior wall were significantly increased, other segments did not change after the operation. The mean systolic strain rate value was significantly increased after the operation. Left ventricle strain values in the middle segment of the septum, middle and basal segments of the inferior wall, and middle and basal segments of the anterior wall were significantly increased after the operation. No significant difference was noted in the basal septum or the middle and basal segments of the lateral wall after the operation. The mean systolic strain value was significantly increased after the operation.

CONCLUSION

The results of this study suggest that strain and strain rate echocardiography can provide an accurate evaluation of regional contractile function after CABG, even in the segments that are apparently normal.

Treatment with the CC chemokine-binding protein Evasin-4 improves post-infarction myocardial injury and survival in mice

Chemokines trigger leukocyte trafficking and are implicated in cardiovascular disease pathophysiology. Chemokine-binding proteins, called "Evasins" have been shown to inhibit both CC and CXC chemokine-mediated bioactivities. Here, we investigated whether treatment with Evasin-3 (CXC chemokine inhibitor) and Evasin-4 (CC chemokine inhibitor) could influence post-infarction myocardial injury and remodelling. C57Bl/6 mice were submitted in vivo to left coronary artery permanent ligature and followed up for different times (up to 21 days). After coronary occlusion, three intraperitoneal injections of 10 μg Evasin-3, 1 μg Evasin-4 or equal volume of vehicle (PBS) were performed at 5 minutes, 24 hours (h) and 48 h after ischaemia onset. Both anti-chemokine treatments were associated with the beneficial reduction in infarct size as compared to controls. This effect was accompanied by a decrease in post-infarction myocardial leukocyte infiltration, reactive oxygen species release, and circulating levels of CXCL1 and CCL2. Treatment with Evasin-4 induced a more potent effect, abrogating the inflammation already at one day after ischaemia onset. At days 1 and 21 after ischaemia onset, both anti-chemokine treatments failed to significantly improve cardiac function, remodelling and scar formation. At 21-day follow-up, mouse survival was exclusively improved by Evasin-4 treatment when compared to control vehicle. In conclusion, we showed that the selective inhibition of CC chemokines (i.e. CCL5) with Evasin-4 reduced cardiac injury/inflammation and improved survival. Despite the inhibition of CXC chemokine bioactivities, Evasin-3 did not affect mouse survival. Therefore, early inhibition of CC chemokines might represent a promising therapeutic approach to reduce the development of post-infarction heart failure in mice.

The most important publications of the past year in echocardiography

We review the published literature on clinical echocardiography of the past year. Key topics were valvular heart disease, in particular aortic stenosis, and the imaging requirements for transcatheter aortic valve implantation. Three-dimensional echocardiography and deformation imaging have yielded important new insights in valvular heart disease. Other key fields have been assessment of heart failure, in particular heart failure with preserved ejection fraction, and the relationship of this condition with diastolic dysfunction and left atrial function. Functional imaging of cardiomyopathies was also an important topic.

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.