Myocardial layer-specific analysis of ischemic memory using speckle tracking echocardiography

Myocardial motion in acute ischemia: revealing invisible deformation by echocardiography

Echocardiography has been used clinically to assess regional myocardial wall motion for the diagnosis of acute myocardial ischemia or stress-induced ischemia, but it is often difficult to distinguish hypokinetic motion from normal motion. Myocardial wall motion is affected by loading conditions as well as intrinsic contractility, making it challenging to define a normal range of wall motion. Therefore, hypokinesis is usually diagnosed by comparing target areas with other areas of myocardium considered normal (relative hypokinesis). Myocardial strain analysis by tissue Doppler echocardiography and speckle-tracking echocardiography has enabled objective and quantitative evaluation of regional myocardial wall motion. Peak systolic strain decreases during acute ischemia, but subtle and invisible myocardial motion, such as early systolic lengthening (ESL) and postsystolic shortening (PSS), also occurs, and the analysis of these subtle motions can improve the diagnostic accuracy of ischemia. However, the diagnosis of ischemic myocardium by strain analysis is not widely performed in clinical practice at this time due to several limitations. This article reviews the features of myocardial motion during acute ischemia, the mechanisms of ESL and PSS, the diagnosis of ischemic myocardium using strain analysis, and current approaches and future challenges to overcome the limitations in the detection of relative hypokinesis. This article also explains the use of ESL and PSS to detect myocardial ischemic memory that remains after brief ischemia.

Research Progress of Myocardial Fibrosis and Atrial Fibrillation

With the aging population and the increasing incidence of basic illnesses such as hypertension and diabetes (DM), the incidence of atrial fibrillation (AF) has increased significantly. AF is the most common arrhythmia in clinical practice, which can cause heart failure (HF) and ischemic stroke (IS), increasing disability and mortality. Current studies point out that myocardial fibrosis (MF) is one of the most critical substrates for the occurrence and maintenance of AF. Although myocardial biopsy is the gold standard for evaluating MF, it is rarely used in clinical practice because it is an invasive procedure. In addition, serological indicators and imaging methods have also been used to evaluate MF. Nevertheless, the accuracy of serological markers in evaluating MF is controversial. This review focuses on the pathogenesis of MF, serological evaluation, imaging evaluation, and anti-fibrosis treatment to discuss the existing problems and provide new ideas for MF and AF evaluation and treatment.

Myocardial Postsystolic Shortening and Early Systolic Lengthening: Current Status and Future Directions

The concept of paradoxical myocardial deformation, commonly referred to as postsystolic shortening and early systolic lengthening, was originally described in the 1970s when assessed by invasive cardiac methods, such as ventriculograms, in patients with ischemia and animal experimental models. Today, novel tissue-based imaging technology has revealed that these phenomena occur far more frequently than first described. This article defines these deformational patterns, summarizes current knowledge about their existence and highlights the clinical potential associated with their understanding.

[Echocardiography in the Assessment of Postsystolic Shortening of the Left Ventricle Myocardium of the Heart]

Echocardiography allows evaluating left ventricular (LV) myocardial contractility; however, the visual assessment of contractility is subjective and requires considerable experience. Modern technologies for assessment of LV myocardial contractility, such as tissue Doppler and speckle-tracking echocardiography, provide quantitative estimation of various parameters of myocardial strain, including the LV postsystolic shortening. Several studies have demonstrated the value of postsystolic shortening for evaluation of myocardial ischemia and "ischemic memory" in patients with cardiovascular diseases. This review analyzes experimental and clinical studies that addressed LV postsystolic shortening.

Serial assessment of focal myocardial function after percutaneous coronary intervention for ST-elevation myocardial infarction: Value of layer-specific speckle tracking echocardiography

BACKGROUND

Ischemia-reperfusion injury (IRI) frequently follows successful PCI for STEMI and is recognized by multiple modalities. Multilayer speckle tracking echocardiography (STE) has the potential of detecting myocardial dysfunction in different myocardial layers. Our objective was to describe the changes in layer-specific myocardial function over the 24 hours after successful PCI for ST-elevation myocardial infarction (STEMI).

METHODS

Patients (n = 120) with STEMI and no prior myocardial infarction underwent echocardiography prior to PCI, immediately after and at 3- and 24-hours post-PCI. Worsening focal dysfunction (WFD) was defined as an immediate reduction, compared to the pre-PCI value, in the amplitude of endo-myocardial longitudinal strain (endo-MLS) within the infarction territory.

RESULTS

Patients with WFD (52%) had further reductions in endo-MLS, mid-MLS, and epi-MLS in the infarction region immediately post-PCI; at 3 hours strain began to improve and continued to improve at 24 hours. Reductions of endo-MLS strain were more evident than those of global, mid-MLS, and epi-MLS. This same pattern was seen in each of the ischemic territories of the anterior descending, circumflex, and right coronary arteries. Immediate improvement in endo-MLS following PCI was seen in 48% of patients. The time from symptom onset to balloon time was markedly longer in those with WFD (P < .0001).

CONCLUSIONS

Multilayer SPE is a sensitive method that identifies serial alterations in focal myocardial function following successful PCI for STEMI. Layer-specific reductions in endo-MLS appeared more evident than decreases in global LV strain. Prolonged total ischemic time prior to PCI was directly related to the incidence of WFD.

Regional heterogeneity of afterload sensitivity in myocardial strain

PURPOSE

The peak systolic strain decreases due to afterload augmentation. However, its deterioration (i.e., afterload sensitivity) may be different within the left ventricular (LV) segments. We investigated how afterload influences regional strain and whether there is regional heterogeneity of afterload sensitivity.

METHODS

Afterload was increased by aortic banding in 20 open-chest dogs. Short-axis images were acquired at baseline and during banding. Circumferential strain was analyzed in six segments, and the absolute decrease in the peak systolic strain during banding (Δε) was calculated for each segment. To assess the effect of the compensatory preload recruitment during banding, the endocardial lengths of the septum and free wall were measured at end-diastole, and the rate of increase due to banding was calculated.

RESULTS

LV systolic pressure was significantly increased during banding (100 ± 14 vs. 143 ± 18 mmHg, P < 0.001). The peak systolic strain in all segments was significantly decreased during banding. Δɛ in the anterior segment, which is a part of the free wall, was significantly lower than that in the inferoseptal segment (2.6 ± 4.7 vs. 6.5 ± 3.5%, P = 0.035). The rate of increase in endocardial length in the free wall was significantly larger than that in the septum (15.6 ± 10.4 vs. 8.1 ± 7.4%, P = 0.014).

CONCLUSION

The decrease in septal strain during afterload augmentation was larger than that in free wall strain, indicating that there was regional heterogeneity of afterload sensitivity in circumferential strain. The larger compensatory preload recruitment in the free wall than in the septum is implicated as a cause of the heterogeneity.

The relationship between functional capacity and left ventricular strain in patients with uncomplicated type 2 diabetes

OBJECTIVE

We aimed to evaluate the association between functional capacity and left ventricular (LV) mechanics in the patients with uncomplicated type 2 diabetes.

METHODS

The present cross-sectional study included 80 controls and 70 uncomplicated diabetic patients. These participants underwent laboratory analysis, comprehensive echocardiographic examination and cardiopulmonary exercise testing.

RESULTS

Global longitudinal (-21.6 ± 2.8 vs. -18.4 ± 2.3%, P < 0.001) and circumferential (-22.0 ± 2.9 vs. -19.5 ± 2.6%, P < 0.001) strains were significantly reduced in diabetic participants. The same was found for longitudinal and circumferential endocardial, mid-myocardial and epicardial strains. Peak oxygen uptake (27.0 ± 4.3 vs. 20.7 ± 4.0 ml/kg/min, P < 0.001) and oxygen pulse (14.1 ± 3.0 vs. 11.6 ± 3.2 ml/beat, P < 0.001) were significantly lower in the diabetic group, while ventilation/carbon dioxide slope was significantly higher in these patients. In the whole study population glycosylated hemoglobin, as well as LV endocardial longitudinal and circumferential strains were independently of other clinical and echocardiographic parameters of LV structure, systolic and diastolic function associated with peak oxygen consumption and oxygen pulse.

CONCLUSION

Our investigation showed that diabetes equally affected all LV myocardial layers. Endocardial LV longitudinal and circumferential strains, as well as glycosylated hemoglobin - main parameter of glucose regulation, were independently associated with functional capacity in the whole study population. These findings indicate that determination of LV strain and functional capacity could detect subclinical target organ damage and prevent development of further complications in uncomplicated diabetes mellitus patients.

Deterioration of longitudinal, circumferential, and radial myocardial strains during acute coronary flow reduction: which direction of strain should be analyzed for early detection?

Longitudinal myocardial strain is considered to deteriorate in the early ischemic stage compared to circumferential and radial strains because the subendocardial inner oblique fibers are generally directed along the longitudinal axis. However, it is unclear whether the decrease in longitudinal strain precedes a decrease in circumferential and radial strains during acute coronary flow reduction. The left anterior descending artery was gradually narrowed in 13 open-chest dogs. Whole-wall and subendocardial longitudinal, circumferential, and radial strains were analyzed at baseline and during flow reduction. Peak systolic and end-systolic strains, the postsystolic strain index (PSI), and the early systolic strain index (ESI) were measured in the risk area; the decreasing rate in each parameter and the diagnostic accuracy to detect flow reduction were evaluated. Absolute values of peak systolic and end-systolic strains gradually decreased with flow reduction. The decreasing rate and diagnostic accuracy of longitudinal systolic strain were not significantly different from those in other strains, although the diagnostic accuracy of radial systolic strain tended to be lower. PSI and ESI gradually increased with flow reduction. In these parameters, a lower diagnostic accuracy with respect to radial strain was not demonstrated. During acute coronary flow reduction, the decrease in longitudinal systolic strain did not precede that in circumferential systolic strain; however, the decrease in radial systolic strain may be smaller than that of other systolic strains. In contrast, there appeared to be no differences in the PSI and ESI values among the three strains.

Assessment of Myocardial Ischemic Memory Using Three-Dimensional Speckle-Tracking Echocardiography: A Novel Integrated Analysis of Early Systolic Lengthening and Postsystolic Shortening

BACKGROUND

Persistence of subtle abnormal myocardial deformation such as postsystolic shortening (PSS) after transient ischemia can be used to diagnose a history of myocardial ischemia (myocardial ischemic memory). Furthermore, early systolic lengthening (ESL) has recently attracted attention as another marker of myocardial ischemia. However, it is unclear whether the persistence of such abnormal deformation can be detected by three-dimensional (3D) speckle-tracking echocardiography, which has relatively low spatial and temporal resolution compared with two-dimensional echocardiography. The aim of this study was to evaluate the diagnostic accuracy of myocardial ischemic memory and its spatial extent using 3D speckle-tracking echocardiography.

METHODS

The left circumflex coronary artery was occluded for 2 min, followed by reperfusion, in 33 dogs. Their hemodynamic and 3D echocardiographic data were chronologically acquired. Peak systolic strain, early systolic strain index as a parameter of ESL, postsystolic strain index as a parameter of PSS, and myocardial dysfunction index as a combined parameter of ESL and PSS were analyzed in all left ventricular segments.

RESULTS

At the center of the risk area, early systolic strain index and postsystolic strain index significantly increased until 20 min after reperfusion compared with baseline, although peak systolic strain recovered by 20 min. Myocardial dysfunction index significantly increased for >20 min after reperfusion and allowed better diagnostic accuracy of ischemic memory than the other parameters. In the 147 risk segments, abnormal values of myocardial dysfunction index remained in 49 segments (33%) at 20 min after reperfusion, whereas abnormal peak systolic strain was observed in only 13 segments (9%).

CONCLUSIONS

ESL and PSS persisted after transient ischemia and could be detected by 3D speckle-tracking echocardiography. Integrated analysis of ESL and PSS provided higher diagnostic accuracy of ischemic memory. This method may be useful for detecting transient ischemic insults in patients after the disappearance of anginal attack.

Right Heart Remodeling in Patients with End-Stage Alcoholic Liver Cirrhosis: Speckle Tracking Point of View

BACKGROUND

Data regarding cardiac remodeling in patients with alcoholic liver cirrhosis are scarce. We sought to investigate right atrial (RA) and right ventricular (RV) structure, function, and mechanics in patients with alcoholic liver cirrhosis.

METHODS

This retrospective cross-sectional investigation included 67 end-stage cirrhotic patients, who were referred for evaluation for liver transplantation and 36 healthy controls. All participants underwent echocardiographic examination including strain analysis, which was performed offline.

RESULTS

RV basal diameter and RV thickness were significantly higher in patients with cirrhosis. Conventional parameters of the RV systolic function were similar between the observed groups. Global, endocardial, and epicardial RV longitudinal strains were significantly lower in patients with cirrhosis. Active RA function was significantly higher in cirrhotic patients than in controls. The RA reservoir and conduit strains were significantly lower in cirrhotic patients, while there was no difference in the RA contractile strain. Early diastolic and systolic RA strain rates were significantly lower in cirrhotic patients than in controls, whereas there was no difference in the RA late diastolic strain rate between the two groups. Transaminases and bilirubin correlated negatively with RV global longitudinal strain and RV-free wall strain in patients with end-stage liver cirrhosis. The Model for End-stage Liver Disease (MELD) score, predictor of 3-month mortality, correlated with parameters of RV structure and systolic function, and RA active function in patients with end-stage liver cirrhosis.

CONCLUSIONS

RA and RV remodeling is present in patients with end-stage liver cirrhosis even though RV systolic function is preserved. Liver enzymes, bilirubin, and the MELD score correlated with RV and RA remodeling.

Left Ventricular Strain and Dyssynchrony in Young and Middle-Aged Peritoneal Dialysis Patients and Healthy Controls: A Case-Matched Study

BACKGROUND

This study aimed to evaluate the role of two-dimensional speckle-tracking imaging (2D-STI) and myocardial layer-specific analysis in evaluating early left ventricular (LV) myocardial function and systolic dyssynchrony in young and middle-aged uremic patients undergoing peritoneal dialysis (PD).

METHODS

We enrolled 31 PD patients aged ≤65 years with preserved LV ejection fraction (LVEF, ≥54%) as the PD group and 49 age-matched healthy people as the control group. Echocardiography was used to assess the left atrial diameter index (LADI, LAD/BSA), LV mass index (LVMI), LVEF, peak early diastolic velocity/late diastolic velocity (E/A) (measured by pulsed Doppler), and peak early diastolic velocity (by pulsed Doppler)/peak velocity of the early diastolic wave (by pulsed-wave tissue Doppler) (E/e'). Next, we used 2D-STI and myocardial layer-specific analysis to obtain longitudinal strains (LS) of the endocardium (LSendo), the myocardium (LSmyo), the epicardium (LSepi), and the global myocardium (GLS). Then, we measured the postsystolic index (PSI) to evaluate LV myocardial function. Time to peak LS (TTP) and peak strain dispersion (PSD) from 17 consecutive segments were assessed to quantify LV dyssynchrony.

RESULTS

Compared with the controls, PD patients had significantly increased LADI (p = 0.041), LVMI (p = 0.000), and E/e' (p = 0.009), but reduced LVEF (p = 0.000) and E/A (p = 0.000). The average values of GLS (GLS avg) (p = 0.01) and GLS of the apical 2-chamber view (p = 0.003), including the LSendo (p = 0.024), LSmyo (p = 0.024), and LSepi (p = 0.032), were significantly decreased in patients with PD compared with controls. In PSI, segments of LS were markedly delayed in the anterior septum (p = 0.047), anterior (p = 0.000) and septum wall (p = 0.024) from basal segments, anterior wall (p = 0.001) from middle segments, and anterior (p = 0.024) and inferior (p = 0.024) wall from apical segments. Moreover, PSD was significantly increased in PD patients (p = 0.015), while TTP was evidently delayed in the anterior septum (p = 0.004), anterior (p = 0.000) and posterior (p = 0.042) wall from basal segments, and inferior wall (p = 0.048) from apical segments.

CONCLUSIONS

Despite preserved LVEF, young and middle-aged PD patients developed LV dysfunction and myocardial systolic dyssynchrony earlier compared with controls.

Layer-specific deformation of the left ventricle in uncomplicated patients with type 2 diabetes and arterial hypertension

BACKGROUND

Detailed analysis of layer-specific mechanical changes in patients with type 2 diabetes mellitus (DM) might improve insight into left ventricular (LV) remodelling and diabetic cardiomyopathy.

AIM

We sought to investigate layer-specific LV deformation in patients with DM, with and without hypertension.

METHODS

This cross-sectional study included 146 subjects (44 controls; 48 patients with DM; 54 patients with DM and hypertension) who underwent complete examination by two-dimensional echocardiography (2DE), including multilayer strain analysis.

RESULTS

2DE LV longitudinal and circumferential strains deteriorated progressively and significantly from controls, through patients with DM, to patients with DM and hypertension. 2DE radial strain was lower in patients with DM and hypertension than in controls. 2DE longitudinal and circumferential mid-myocardial and epicardial layer strains decreased progressively from controls to patients with DM and hypertension, whereas endocardial layer strain was lower in patients with DM and patients with DM and hypertension than in controls. Variables of DM control (fasting glucose and glycated haemoglobin) were associated with 2DE LV longitudinal and circumferential layer-specific strains, independent of age, body mass index, blood pressure, LV diastolic function and hypertrophy in patients with DM.

CONCLUSION

DM and hypertension significantly affect LV deformation assessed by 2DE traditional strain and 2DE multilayer strain. Hypertension showed an additional negative effect on LV deformation in patients with DM. Fasting glucose and glycated haemoglobin were associated with LV mechanics evaluated by comprehensive 2DE strain analysis, independent of LV structure and diastolic function.

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.

Diagnostic value of layer-specific global longitudinal strain during adenosine stress in patients suspected of coronary artery disease

Speckle tracking global longitudinal strain (GLS) from dobutamine stress echocardiography (SE) predicts coronary artery disease (CAD). The diagnostic value of GLS from vasodilator SE and the additional value of layer-specific speckle tracking analysis are unclear. We explored the usefulness of layer-specific GLS and non-layer-specific strain (automated functional imaging, AFI) from adenosine SE. The included 132 patients (67% male, 62.6 (9.0) years), of which 46 (35%) had CAD defined as ≥1 stenosis ≥70% (≥50% in the left main), underwent adenosine SE and invasive coronary angiography. Resting AFI and layer-specific GLS were similar in patients with or without CAD (p > 0.05). The stress-rest difference (Δvalue = stress-value - rest-value) in patients with CAD was less pronounced compared to patients without proved CAD (Δendocardial GLS: -1.2 (3.5)% vs. -5.0 (3.2)%; Δmidventricular GLS: -0.95 (3.0)% vs. -4.2 (2.7)%; Δepicardial GLS: -0.7 (2.5)% vs. -3.4 (2.3)%; ΔAFI: -0.8 (2.9)% vs. -3.6 (3.1)%, p < 0.00001 for all comparisons). The diagnostic value of the three layer-specific GLS values and AFI were statistically similar (p = 0.19). The four Δvalues provided independent predictive value to the risk assessment given by gender, age, wall motion and ΔEF (p = 0.002, AFI and p < 0.0001, layer-specific GLS). The accuracies were acceptable (71-80%) with modest sensitivities (54-65%) and high specificities (80-91%). The deformation response to vasodilator infusion was associated with the presence of CAD. Endocardial, midventricular and epicardial GLS and AFI from adenosine SE had similar diagnostic values. The specificities were high, but the modest sensitivities are a limitation to the clinical application.

Different responses of the myocardial contractility by layer following acute pressure unloading in severe aortic stenosis patients

The present study evaluated change in left ventricle (LV) biomechanics, layer-by-layer, following acute pressure unloading in patients with severe aortic stenosis (AS). In twenty-eight consecutive patients with severe AS who underwent transcatheter aortic valve replacement (TAVR), LV peak global longitudinal and circumferential strains of the endo-, midmyo- and epicardium were evaluated using multilayer speckle tracking echocardiography before, 1 week after, and 1 month after TAVR. Longitudinal and circumferential strains were significantly highest in the endocardium and lowest in the epicardium at baseline. At 1 month following TAVR, longitudinal strain significantly improved in all layers compared with the baseline [endocardium (%) -16.7 ± 3.8 vs. -18.6 ± 3.3, P = 0.01; mid-myocardium -14.4 ± 3.2 vs. -16.2 ± 3.5, P < 0.01; epicardium -12.4 ± 2.8 vs. -13.6 ± 2.6, P = 0.01], whereas LV ejection fraction and circumferential strain remained unchanged. Importantly, only those with LV hypertrophy demonstrated improved longitudinal strain [endocardium (%) -15.7 ± 3.0 vs. -18.7 ± 2.9, P < 0.01; mid-myocardium -13.6 ± 2.7 vs. -16.0 ± 2.5, P < 0.01; epicardium -11.8 ± 2.4 vs. -13.7 ± 2.3, P < 0.01]. The improvement in longitudinal strain was more prominent in the endocardium, which was evident even at an early time point (1 week) after TAVR. Longitudinal strain significantly improved in all three layers following acute pressure unloading, the most prominent of which was observed in the endocardium. Evaluation of multilayer strain may provide new insights into the LV mechanics in the future.

Compensatory increase of left atrial external work to left ventricular dysfunction caused by afterload increase

Afterload mismatch can cause acute decompensation leading to an occurrence of acute heart failure. We investigated how the left atrium (LA) and left ventricle (LV) react to acute increases in afterload using speckle tracking echocardiography (STE). LA strain and volume were obtained by STE in 10 dogs during banding of descending aorta (AoB). Simultaneously, LA pressure was measured by a micromanometer-tipped catheter. LA peak negative strain during LA contraction, strain change during LA relaxation (early reservoir strain), and that during LA dilatation (late reservoir strain) were obtained from LA longitudinal strain-volume curves. From pressure-strain curves, the areas of A-loop and V-loops were computed as the work during active contraction and relaxation (A-work) and that during passive filling and emptying (V-work). AoB increased LV systolic pressure (105 ± 15 vs. 163 ± 12 mmHg, P < 0.01) and mean LA pressure (3.8 ± 1.2 vs. 7.1 ± 2.0 mmHg, P < 0.01). LV global circumferential strain decreased (−18.8 ± 3.5 vs. −13.2 ± 3.5%, P < 0.01), but LV stroke volume was maintained (8.4 ± 2.3 vs. 9.6 ± 3.6 ml). LA peak negative strain (−2.9 ± 2.3 vs. −9.8 ± 4.0%, P < 0.01) and early reservoir strain (4.5 ± 2.1 vs. 7.7 ± 2.4%, P < 0.05) increased by AoB, but late reservoir strain did not change (8.9 ± 3.4 vs. 6.1 ± 3.4%). A-work significantly increased (3.2 ± 2.0 vs. 19.2 ± 15.1 mmHg %, P < 0.01), whereas V-work did not change (13.3 ± 7.1 vs. 13.1 ± 7.7 mmHg %). In conclusion, LA external work during active contraction and relaxation increased as compensation for LV dysfunction during aortic banding. Atrial dysfunction may lead failure of this mechanism and hemodynamic decompensation.

Visually confirmed post-systolic shortening during the recovery period in four cases of Takotsubo cardiomyopathy

We report visually confirmed post-systolic shortening (PSS) during the recovery period and the relationship between PSS and electrocardiographic abnormalities in 4 cases of Takotsubo cardiomyopathy (TTC). In these 4 cases, the appearance of visually confirmed PSS during the recovery period coincided with observation of the deepest T wave and the longest QT interval. The transmural repolarization gradient and heterogeneous duration of myocardial contractions may cause PSS in the TTC recovery period.