Association between Multilayer Left Ventricular Rotational Mechanics and the Development of Left Ventricular Remodeling after Acute Myocardial Infarction

Cardiovascular magnetic resonance imaging of functional and microstructural changes of the heart in a longitudinal pig model of acute to chronic myocardial infarction

BACKGROUND

We examined the dynamic response of the myocardium to infarction in a longitudinal porcine study using relaxometry, functional as well as diffusion cardiovascular magnetic resonance (CMR). We sought to compare non contrast CMR methods like relaxometry and in-vivo diffusion to contrast enhanced imaging and investigate the link of microstructural and functional changes in the acute and chronically infarcted heart.

METHODS

CMR was performed on five myocardial infarction pigs and four healthy controls. In the infarction group, measurements were obtained 2 weeks before 90 min occlusion of the left circumflex artery, 6 days after ischemia and at 5 as well as 9 weeks as chronic follow-up. The timing of measurements was replicated in the control cohort. Imaging consisted of functional cine imaging, 3D tagging, T2 mapping, native as well as gadolinium enhanced T1 mapping, cardiac diffusion tensor imaging, and late gadolinium enhancement imaging.

RESULTS

Native T1, extracellular volume (ECV) and mean diffusivity (MD) were significantly elevated in the infarcted region while fractional anisotropy (FA) was significantly reduced. During the transition from acute to chronic stages, native T1 presented minor changes (< 3%). ECV as well as MD increased from acute to the chronic stages compared to baseline: ECV: 125 ± 24% (day 6) 157 ± 24% (week 5) 146 ± 60% (week 9), MD: 17 ± 7% (day 6) 33 ± 14% (week 5) 29 ± 15% (week 9) and FA was further reduced: - 31 ± 10% (day 6) - 38 ± 8% (week 5) - 36 ± 14% (week 9). T2 as marker for myocardial edema was significantly increased in the ischemic area only during the acute stage (83 ± 3 ms infarction vs. 58 ± 2 ms control p < 0.001 and 61 ± 2 ms in the remote area p < 0.001). The analysis of functional imaging revealed reduced left ventricular ejection fraction, global longitudinal strain and torsion in the infarct group. At the same time the transmural helix angle (HA) gradient was steeper in the chronic follow-up and a correlation between longitudinal strain and transmural HA gradient was detected (r = 0.59 with p < 0.05). Comparing non-gadolinium enhanced data T2 mapping showed the largest relative change between infarct and remote during the acute stage (+ 33 ± 4% day 6, with p = 0.013 T2 vs. MD, p = 0.009 T2 vs. FA and p = 0.01 T2 vs. T1) while FA exhibited the largest relative change between infarct and remote during the chronic follow-up (+ 31 ± 2% week 5, with p = N.S. FA vs. MD, p = 0.03 FA vs. T2 and p = 0.003 FA vs. T1). Overall, diffusion parameters provided a higher contrast (> 23% for MD and > 27% for FA) during follow-up compared to relaxometry (T1 17-18%/T2 10-20%).

CONCLUSION

During chronic follow-up after myocardial infarction, cardiac diffusion tensor imaging provides a higher sensitivity for mapping microstructural alterations when compared to non-contrast enhanced relaxometry with the added benefit of providing directional tensor information to assess remodelling of myocyte aggregate orientations, which cannot be otherwise assessed.

Prognostic Value of Multilayer Left Ventricular Global Longitudinal Strain in Patients with ST-segment Elevation Myocardial Infarction with Mildly Reduced Left Ventricular Ejection Fractions

Multilayer (epi-, mid- and endocardium) left ventricular (LV) global longitudinal strain (GLS) reflects the extent of myocardial damage after ST-segment myocardial infarction (STEMI). However, the prognostic implications of multilayer LV GLS remain unclear. We studied the association between multilayer LV GLS and prognosis in patients with mildly reduced or preserved LV ejection fraction (EF) after STEMI. Patients with first STEMI and LVEF>45% were evaluated retrospectively. Baseline multilayer (endocardial, mid-myocardial and epicardial) LV GLS were measured on 2-dimensional speckle tracking echocardiography. Patients were followed up for of all-cause mortality. A total of 569 patients (77% male, 60 ± 11 years) were included. After a median follow-up of 117 (interquartile range 106-132) months, 95 (17%) patients died. We observed no differences in baseline LVEF and peak troponin levels between survivors and non-survivors. However, non-survivors showed more impaired GLS at all layers (epicardium: -11.9 ± 2.8% vs. -13.4 ± 2.8%; mid-myocardium: -14.2 ± 3.2% vs. -15.6 ± 3.2%; endocardium: -16.5 ± 3.7% vs. -17.7 ± 3.6%, p <0.05, for all). On multivariable analysis, increasing age (hazard ratio 1.095; p<0.001) and impaired LV GLS of the epicardial layer (hazard ratio 1.085; p = 0.047) were independently associated with higher risk of all-cause mortality. In addition, LV GLS at the epicardium had incremental prognostic value for all-cause mortality (χ² = 114, p = 0.044). In conclusion, in contemporary STEMI patients with mildly reduced or preserved LVEF, ageing and reduced LV GLS of the epicardium (reflecting transmural scar formation) were independently associated with all-cause mortality after adjusting for clinical and echocardiographic variables.

A multidimensional sight on cardiac failure: uncovered from structural to molecular level

Heart failure is one of the leading causes of death, with high mortality rate within 5 years after diagnosis. Treatment and prognosis options for heart failure primarily targeted on hemodynamic and neurohumoral components that drive progressive deterioration of the heart. However, given the multifactorial background that eventually leads to the "phenotype" named heart failure, better insight into the various components may lead to personalized treatment opportunities. Indeed, currently used criteria to diagnose and/or classify heart failure are possibly too focused on phenotypic improvement rather than the molecular driver of the disease and could therefore be further refined by integrating the leap of molecular and cellular knowledge. The ambiguity of the ejection fraction-based classification criteria became evident with development of advanced molecular techniques and the dawn of omics disciplines which introduced the idea that disease is caused by a myriad of cellular and molecular processes rather than a single event or pathway. The fact that different signaling pathways may underlie similar clinical manifestations calls for a more holistic study of heart failure. In this context, the systems biology approach can offer a better understanding of how different components of a system are altered during disease and how they interact with each other, potentially leading to improved diagnosis and classification of this condition. This review is aimed at addressing heart failure through a multilayer approach that covers individually some of the anatomical, morphological, functional, and tissue aspects, with focus on cellular and subcellular features as an alternative insight into new therapeutic opportunities.

Effect of Transmural Extent of the Simulated Infarction in a Left Ventricular Model on Displacement and Strain Distribution Estimated from Synthetic Ultrasonic Data

The identification of a sub-endocardial infarction is of major interest in cardiology. This study evaluates the sensitivity of selected measures to the thickness of such an infarction. Synthetic ultrasonic data (long-axis view) of left ventricular models with inclusions were generated using Field II and meshes obtained from finite-element simulations, which also provided the reference for the estimates obtained from ultrasonic data. The displacements, the first and second component of the principal strain (ε₁ and ε₂), and several measures derived from these quantities were estimated. All estimates, except for the poorly estimated ε₂, exhibited sensitivity to the presence and transmurality of the inclusion. The most sensitive was the gradient of the averaged transmural profiles of ε₁, and ε₁ averaged over the area corresponding to the transmural inclusion. The inflection point of the ε₁ profile shifted toward the outer wall with increasing thickness of the non-transmural inclusion.

Prediction of Left Ventricular Remodeling after a Myocardial Infarction: Role of Myocardial Deformation: A Systematic Review and Meta-Analysis

Aims

Left ventricular (LV) adverse or reverse remodeling after ST-segment elevation myocardial infarction (MI) is the best outcome to assess the benefit of revascularization. Speckle tracking echocardiography (STE) may accurately identify early deformation impairment, while also being predictive of LV remodeling during follow-up. This systematic analysis aimed to provide a comprehensive review of current findings on STE as a predictor of LV remodeling after MI.

Methods

PubMed databases were searched through December 2014 to identify studies in adults targeting the association between LV remodeling and STE. Meta-regression was performed for longitudinal analysis.

Results

A total of 23 prospective studies (3066 patients) were found eligible. Eleven studies reported an association between STE and adverse remodeling and twelve studies with reverse remodeling. Using peak systolic longitudinal strain, the most accurate cut-off to predict adverse remodeling and reverse remodeling ranged from -12.8% to -10.2% and from -13.7% to -9.5%, respectively. In smaller studies, assessment of circumferential strain and torsion showed additive value in predicting remodeling. Meta-regression analysis revealed that longitudinal STE was associated with adverse remodeling (pooled univariable OR = 1.27, 1.17–1.38, p<0.001; pooled multivariable OR = 1.38, 1.13–1.70, p = 0.002) while pooled ORs of longitudinal STE only tended to predict reverse remodeling (pooled OR = 0.75, 0.54–1.06, p = 0.09).

Conclusions

This systematic review suggests that STE is associated with changes in LV volume or function regardless of underlying mechanisms and deformation direction. Meta-regression demonstrates a strong association between peak longitudinal systolic strain and adverse remodeling. Added STE predictive value over other clinical, biological and imaging variables remains to be proven.

Two-Dimensional Speckle Tracking Echocardiography Predict Left Ventricular Remodeling after Acute Myocardial Infarction in Patients with Preserved Ejection Fraction

Objectives

Left ventricular remodeling after acute myocardial infarction increases cardiovascular events and mortality. But few study was done in patients with preserved ejection fraction (EF > 40%). We investigate whether the strain and strain rate by 2D speckle tracking echocardiography could predict left ventricular remodeling after acute myocardial infarction in this cohort.

Methods

The 83 patients (average age 60.7 ± 12.3 y, 75 [90.4%] male) with new-onset acute myocardial infarction receiving echocardiography immediately, and 6 months after admission were grouped by the presence or absence of left ventricular remodeling. Strain and strain rate including longitudinal, circumferential, and radial direction were calculated. The average of strain and strain rate of which segmental longitudinal strains > – 15% were defined as the injury longitudinal strain (InjLS).

Results

Left ventricular remodeling occurred in 24 of 83 patients (28.9%). In univariate logistic regression analyses, gender, peak CK-MB, log BNP, use of statin before discharge, wall motion score index, and InjLS were significantly associated with left ventricular remodeling (p < 0.05). In multivariate analysis using the forward stepwise method, gender, CK-MB, and InjLS were independent predictors. The hazard ratio for InjLS was 1.48 (p = 0.04). Receiver operating characteristic curve (ROC) analyses showed the area under the curve (AUC) of InjLS was largest (AUC = 0.75, cut-off value = –11.7%, sensitivity = 81%, specificity = 71%, p < 0.01). In ST-segment elevation myocardial infarction subgroup, InjLS was the only predictor according to ROC analysis (AUC = 0.79, p < 0.01, cut-off value = –11.4%, sensitivity = 88%, specificity = 77%) and multivariate logistic regression analysis (hazard ratio = 1.88, 95% CI: 1.22–2.88, p < 0.01).

Conclusions

InjLS was an excellent predictor for left ventricular remodeling after acute myocardial infarction in patient with preserved ejection fraction.

Advances in Echocardiographic Imaging in Heart Failure With Reduced and Preserved Ejection Fraction

Echocardiography, given its safety, easy availability, and the ability to permit a comprehensive assessment of cardiac structure and function, is an indispensable tool in the evaluation and management of patients with heart failure (HF). From initial phenotyping and risk stratification to providing vital data for guiding therapeutic decision-making and monitoring, echocardiography plays a pivotal role in the care of HF patients. The recent advent of multiparametric approaches for myocardial deformation imaging has provided valuable insights in the pathogenesis of HF, elucidating distinct patterns of myocardial dysfunction and events that are associated with progression from subclinical stage to overt HF. At the same time, miniaturization of echocardiography has further expanded clinical application of echocardiography, with the use of pocket cardiac ultrasound as an adjunct to physical examination demonstrated to improve diagnostic accuracy and risk stratification. Furthermore, ongoing advances in the field of big data analytics promise to create an exciting opportunity to operationalize precision medicine as the new approach to healthcare delivery that aims to individualize patient care by integrating data extracted from clinical, laboratory, echocardiographic, and genetic assessments. The present review summarizes the recent advances in the field of echocardiography, with emphasis on their role in HF phenotyping, risk stratification, and optimizing clinical outcomes.

Echocardiographic Predictors for Left Ventricular Remodeling after Acute ST Elevation Myocardial Infarction with Low Risk Group: Speckle Tracking Analysis

BACKGROUND

We sought to assess echocardiographic predictors of left ventricular (LV) adverse remodeling after successfully reperfused acute ST elevation myocardial infarction (STEMI). LV remodeling is commonly found in STEMI patients and it may suggest adverse outcome in acute myocardial infarction. We sought to identify whether 2D strain and torsion be independent parameters for prediction of LV adverse remodeling.

METHODS

We investigated 208 patients with low-risk STEMI patients who had follow up echocardiography at 6 or more months. After clinical assessments, all patients received revascularization according to current guideline. LV remodeling was defined as > 20% increase in end-diastolic volume (EDV) at follow up.

RESULTS

During the follow-up (11.9 ± 5.3 months), 53 patients (25.5%) showed LV remodeling. In univariate analysis, EDV, end-systolic volume, deceleration time (DT), CK-MB, and global longitudinal strain (GLS) were associated with LV remodeling. In multivariate analysis, EDV [hazard ratio (HR): 0.922, 95% confidence interval (CI): 0.897-0.948, p< 0.001],

GLS (HR

0.842, 95% CI: 0.728-0.974, p = 0.020), DT (HR: 0.989, 95% CI: 0.980-0.998, p = 0.023) and CK-MB (HR: 1.003, 95% CI: 1.000-1.005, p = 0.033) independently predicted LV remodeling. However, global circumferential strain, net twist, and twist or untwist rate were not associated with remodeling.

CONCLUSION

Of various parameters of speckle strain, only GLS predicted adverse remodeling in STEMI patients.

Differential response of LV sublayer twist during dobutamine stress echocardiography as a novel marker of contractile reserve after acute myocardial infarction: relationship with follow-up LVEF improvement

AIMS

Dobutamine stress echocardiography (DSE) is frequently performed to assess left ventricular (LV) contractile reserve in patients following myocardial infarction (STEMI). Given that resting LV sublayer twist assessment has been proposed as a marker of infarct transmurality, this study aimed to investigate whether response of LV subepicardial twist on DSE represents a novel quantitative marker of contractile reserve.

METHODS AND RESULTS

First STEMI patients treated with primary percutaneous coronary intervention with a resting wall motion abnormality in greater than or equal to two segment(s) at 3 months who underwent full protocol DSE were included. Two-dimensional speckle-tracking was used to calculate LV subepi- and subendocardial twist-defined as the net difference (in degrees) of apical and basal rotation for each sublayer-at rest and peak-dose stages. Primary end point was a ≥5% absolute LV ejection fraction (LVEF) improvement between 3 and 6 months. In total, 61 patients (mean age 61 ± 12, 87% male) were included, of whom 48% (n = 29) demonstrated follow-up LVEF improvement. Mean change in both LV subepicardial (ΔLVsubepi) twist (2.4 ± 3.0 vs. 0.00 ± 2.0°, P = 0.001) and LV subendocardial (ΔLVsubendo) twist (2.7 ± 4.5 vs. 0.25 ± 4.5°, P = 0.04) from rest to peak was significantly higher in LVEF improvers. ΔLVsubepi (odds ratio, OR 1.5, 95% confidence interval, CI 1.1-2.0, P = 0.007), but not ΔLVsubendo (OR 1.1, 95% CI 0.99-1.3, P = 0.07), twist was independently associated with follow-up LVEF improvement following adjustment for baseline LVEF and β-blockade.

CONCLUSION

In post-STEMI patients with resting regional dysfunction, the response of LV subepicardial twist on DSE is associated with follow-up LV function improvement, suggesting recruitment in subepicardial function following STEMI reflects greater extent of contractile reserve.

A new 4D trajectory-based approach unveils abnormal LV revolution dynamics in hypertrophic cardiomyopathy

The assessment of left ventricular shape changes during cardiac revolution may be a new step in clinical cardiology to ease early diagnosis and treatment. To quantify these changes, only point registration was adopted and neither Generalized Procrustes Analysis nor Principal Component Analysis were applied as we did previously to study a group of healthy subjects. Here, we extend to patients affected by hypertrophic cardiomyopathy the original approach and preliminarily include genotype positive/phenotype negative individuals to explore the potential that incumbent pathology might also be detected. Using 3D Speckle Tracking Echocardiography, we recorded left ventricular shape of 48 healthy subjects, 24 patients affected by hypertrophic cardiomyopathy and 3 genotype positive/phenotype negative individuals. We then applied Generalized Procrustes Analysis and Principal Component Analysis and inter-individual differences were cleaned by Parallel Transport performed on the tangent space, along the horizontal geodesic, between the per-subject consensuses and the grand mean. Endocardial and epicardial layers were evaluated separately, different from many ecocardiographic applications. Under a common Principal Component Analysis, we then evaluated left ventricle morphological changes (at both layers) explained by first Principal Component scores. Trajectories' shape and orientation were investigated and contrasted. Logistic regression and Receiver Operating Characteristic curves were used to compare these morphometric indicators with traditional 3D Speckle Tracking Echocardiography global parameters. Geometric morphometrics indicators performed better than 3D Speckle Tracking Echocardiography global parameters in recognizing pathology both in systole and diastole. Genotype positive/phenotype negative individuals clustered with patients affected by hypertrophic cardiomyopathy during diastole, suggesting that incumbent pathology may indeed be foreseen by these methods. Left ventricle deformation in patients affected by hypertrophic cardiomyopathy compared to healthy subjects may be assessed by modern shape analysis better than by traditional 3D Speckle Tracking Echocardiography global parameters. Hypertrophic cardiomyopathy pathophysiology was unveiled in a new manner whereby also diastolic phase abnormalities are evident which is more difficult to investigate by traditional ecocardiographic techniques.