1
Master thesis
Department of Cardiology
“Changes in myocardial mechanics after acute myocardial
infarction assessed by speckle tracking echocardiography.”
A thesis submitted in part fulfillment for the degree of Master of Medicine
Tonia Olivia Seeber
Medical Faculty
Supervisor: Dr. Diana Žaliaduonytė-Pekšienė
Lithuanian University of Health Sciences
Kaunas 2016/2017
2
TABLE OF CONTENT
1. Summary ... 3
2. Acknowledgments ... 4
3. Conflicts of interest ... 5
4. Clearance issued by the Ethics Committee ... 6
5. Abbreviations... 7
6. Introduction ... 8
7. Aim and objectives ... 10
8. Literature review ... 11
9. Research methodology and methods ... 15
10. Results ... 19
11. Discussion of the results ... .22
12. Conclusions ... .24
13. Practical recommendations ... .25
3
SUMMARY
Author's name and surname: Tonia Olivia Seeber
Research title: “Changes in myocardial mechanics after acute myocardial infarction assessed by
speckle tracking echocardiography.”
Aim: This study aims to assess global longitudinal peak systolic strain and duration of early systolic
lengthening by speckle tracking echocardiography in patients after MI and evaluate if there is a correlation between global longitudinal peak systolic strain and/or duration of early systolic lengthening and left ventricle remodeling.
Objectives: 1. To assess differences in clinical and echocardiographic characteristics between patients
with left ventricle remodeling and without left ventricle remodeling.
2. To assess the correlation between global longitudinal peak systolic strain, duration of early systolic lengthening and left ventricle remodeling.
Methodology: 54 patients after acute myocardial infarction were assessed by two-dimensional
echocardiography at admission and after three months. Parameters such as: risk factors for ischemic heart disease, infarct-related artery, troponin I, C-reactive protein, left ventricular end-diastolic diameter, left ventricular end-systolic diameter, left ventricular end-diastolic volume, left ventricular end-systolic volume, ejection fraction, wall motion score index, left atrial diameter, peak systolic global longitudinal strain and duration of early systolic lengthening were assessed. The patients were categorized into a group with left ventricle remodeling and a group without left ventricle remodeling. The definition for left ventricle remodeling was set as a ≥15% increase in left ventricular end-diastolic volume at 3-month follow-up compared to the baseline. Parameters were analyzed by SPSS.
Research results: Left ventricular remodeling occurred in 21 of 54 patients. The laboratory parameter
C-reactive protein was significantly associated with left ventricular remodeling (p <0.01). The 21 patients with LV remodeling had a reduced global longitudinal peak systolic strain (p < 0.05) and prolonged duration of early systolic lengthening (p <0.01).
Conclusions:
1. Patients with left ventricle remodeling had higher C-reactive protein and a tendency to have a higher leukocyte level than patients without left ventricle remodeling.
2. Patients with left ventricle remodeling had decreased global longitudinal peak systolic strain and prolonged duration of early systolic lengthening suggesting that patients with following left ventricle remodeling have impaired left ventricle mechanic parameters just after the myocardial infarction while conventional echo parameters do not differ initially.
3. Novel parameters as global longitudinal peak systolic strain and duration of early systolic lengthening are sensitive parameters of left ventricle remodeling prediction.
4
ACKNOWLEDGEMENTS
I would like to express my gratitude to Dr. Diana Žaliaduonytė-Pekšienė and Justina Portacenko for their guidance and efforts throughout this project. Furthermore, I would like to express my appreciation to Prof. Dr. Viktoras Šaferis for his patience and help in the statistical part of this study. Without their participation, the study could not have been successfully performed.
5
CONFLICT OF INTEREST
6
ETHICS COMMITTEE CLEARANCE
The ethics committee in the bioethics centre at Lithuanian University of Health Sciences allows the medical student Tonia Olivia Seeber, from VI course, on 2016-12-21 by her request Nr. BEC-MF-173, to proceed with her scientific research “Changes in myocardial mechanics after acute myocardial infarction assessed by speckle tracking echocardiography”. It consists of assessing global longitudinal peak systolic strain and duration of early systolic lengthening by speckle tracking echocardiography in patients after MI and evaluating if any correlation exists between global longitudinal peak systolic strain and/or duration of early systolic lengthening and left ventricle remodeling.
All the research will be under the supervision of Dr. Diana Žaliaduonytė-Pekšienė from Cardiology Clinic.
7
ABBREVIATION LIST
2D – two-dimensional
2D STE – two-dimensional speckle tracking echocardiography 3D STE – three-dimensional speckle tracking echocardiography ACS – acute coronary syndrome
AMI – acute myocardial infarction CABG – coronary artery bypass graft
ceCMR – contrast-enhanced cardiac magnetic resonance DESL – duration of early systolic lengthening
E/E’ – mitral inflow peak early velocity/ mitral annular peak early velocity ECG – electrocardiography
EF – ejection fraction
GCS – global circumferential strain
GLPSS – global longitudinal peak systolic strain IHD – ischemic heart disease
InjLS – injury longitudinal strain LA – left atrium
LAVI – left atrial volume index LBBB – left bundle branch block LPSS – longitudinal peak systolic strain LV – left ventricle
LVEDV – left ventricular end-diastolic volume LVESD – left ventricular end-systolic diameter LVESV – left ventricular end-systolic volume MI – myocardial infarction
PCI – percutaneous coronary intervention ROC – receiver operating characteristic
SPECT – single photon emission computed tomography STE – speckle tracking echocardiography
STEMI – ST-segment elevation myocardial infarction STI – speckle tracking imaging
TDI – tissue Doppler imaging TnI – troponin I
8
INTRODUCTION
The cardiac cycle consists of two parts, the diastole and the systole. The diastole is a period of relaxation during which the heart fills with blood. This is followed by the systole, a period of contraction. During the cardiac cycle, the left ventricular myocardium deforms in a complex way. This deformation can be visualized by various means. In patients with acute myocardial infarction (MI), it is clinically very important to assess myocardial function accurately. For evaluation of regional myocardial function frequently used methods are: echocardiography (tissue Doppler imaging [TDI] and speckle tracking echocardiography [STE]), contrast-enhanced cardiac magnetic resonance (ceCMR) and single photon emission computed tomography (SPECT). STE has proven to provide a simple and accurate method for assessing left ventricle (LV) function in previous studies [1, 2]. ceCMR is often considered the gold standard for assessment of LV function but it cannot be performed bed-side, is a time-consuming and costly examination and has a low temporal resolution[3]. SPECT has the disadvantage of exposing the patient to a radiation dose.
Two-dimensional speckle tracking echocardiography (2D STE) is an inexpensive method that has good temporal and spatial resolution. It is a grey-scale based technique where the ultrasound beam that is scattered by the tissue produces an image of bright speckles. These speckles are tracked in 2D, along the wall of the LV and not along the ultrasound beam. 2D STE is angle-independent and therefore permits a more comprehensive assessment of myocardial deformation than angle-dependent Doppler imaging [4]. This technique allows the STE software to calculate various parameters. One of them is the percentage change in the systolic longitudinal shortening of the myocardium, i.e. longitudinal peak systolic strain (LPSS) [5].
The values of longitudinal peak systolic strain can be averaged to present global longitudinal peak systolic strain (GLPSS) for assessment of global function. Another novel parameter assessed by STE is duration of early systolic lengthening (DESL). When there is a rise in pressure in the LV during early systole, myocardium that is affected by ischemia will tend to stretch before the onset of systolic shortening. This happens because of its reduced ability to generate active force. The time myocardial segments remain stretched is called DESL.
So far the most established and commonly used method for assessment of systolic LV function is ejection fraction (EF). GLPSS and DESL are evolving as sensitive, more accurate parameters that have been shown to detect myocardial dysfunction very early.
It is very important to estimate the LV systolic function since it is essential for risk evaluation and management of cardiac diseases. For patients after MI the assessment for heart failure plays a major role.
9 Aim of this study is to assess global longitudinal peak systolic strain and duration of early systolic lengthening by speckle tracking echocardiography in patients after MI and evaluate if there is a correlation between global longitudinal peak systolic strain and/or duration of early systolic lengthening and left ventricle remodeling.
10
AIM AND OBJECTIVES OF THE THESIS
Aim:
This study aims to assess global longitudinal peak systolic strain and duration of early systolic lengthening by speckle tracking echocardiography in patients after MI and evaluate if there is a correlation between global longitudinal peak systolic strain and/or duration of early systolic lengthening and left ventricle remodeling.
Objectives:
1. To assess differences in clinical and echocardiographic characteristics between patients with left ventricle remodeling and without left ventricle remodeling.
2. To assess the correlation between global longitudinal peak systolic strain, duration of early systolic lengthening and left ventricle remodeling.
11
LITERATURE REVIEW
The cardiac cycle consists of two parts, the diastole and the systole. The diastole is a period of relaxation during which the heart fills with blood. This is followed by the systole, a period of contraction. During the cardiac cycle, the left ventricular myocardium deforms in a complex way. This deformation can be visualized by various means. In patients with acute myocardial infarction (MI) it is clinically very important to assess myocardial function accurately. It is not only valuable for deciding on medical treatment but also for risk stratification and prognosis assessment following MI [3, 6].
Methods for assessment of LV function
For evaluation of myocardial function echocardiography (tissue Doppler imaging [TDI] and speckle tracking echocardiography [STE]), contrast-enhanced cardiac magnetic resonance (ceCMR) and single photon emission computed tomography (SPECT) are frequently used methods[3].Echocardiography evaluates the LV function and myocardial damage after acute MI primarily by measurement of ejection fraction (EF) and LV volume [6].However, it has to be taken into consideration that theses indices /parameters are global and load dependent. ceCMR is often regarded as the gold standard for assessment of LV function but it cannot be performed bed-side, is a time-consuming and costly examination and has a low temporal resolution [3]. SPECT has the disadvantage of exposing the patient to a radiation dose.
An emerging innovative method has been developed which allows assessing global as well as regional functions – strain imaging based on STE [6]. STE has proven to provide a simple and accurate method for assessing left ventricle (LV) function in previous studies [1, 2]. Two-dimensional speckle tracking echocardiography (2D STE) is an inexpensive method that has good temporal and spatial resolution. It is a grey-scale based technique where the ultrasound beam that is scattered by the tissue produces an image of bright speckles. These speckles are tracked in 2D, along the wall of the LV and not along the ultrasound beam. 2D STE is angle-independent and therefore permits a more comprehensive assessment of myocardial deformation than angle-dependent Doppler imaging [4]. Currently, there is also 3D STE in development which can measure strain in all three directions whereas in 2D STE only two directions of strain can be measured at the same time. So far the temporal and spatial resolution is still lower than in 2D STE and it has to be improved before it is ready for clinical routine use [7].
12 Longitudinal Strain
According to Abduch et al. “Strain is a dimensionless measurement of changes in shape, hence, deformation” [8]. With STE it is possible to elaborate the myocardial deformation in longitudinal, radial and circumferential directions. STE software can calculate myocardial deformation by tracking the percentage of wall lengthening and shortening [9]. According to Bansal et al. “As the myocardium shortens during systole, the strain and strain rate have negative value but when there is stretch or lengthening of the myocardium, the strain and strain rate become positive” [4].
STI enables calculation of the percentage change in the systolic longitudinal shortening of the myocardium, i.e. longitudinal peak systolic strain (LPSS) [5]. The values of longitudinal peak systolic strain (LPSS) can be averaged to present global longitudinal peak systolic strain (GLPSS) for assessment of global function.
Longitudinal strain and Ejection Fraction
A study of Mizuguchi et al [10] showed that longitudinal strain seems to be the earliest to be affected by ischemia as the subendocardial fibers are the first to suffer the effects of perfusion abnormalities. Longitudinal myocardial fibers are predominantly found in the subendocardium which is the layer most susceptible to ischemia. Other studies also conclude that longitudinal strain is the most vulnerable and sensitive to show that the myocardium is damaged due to that fact and therefore superior to LVEF in detecting myocardial dysfunction [11, 12].
The study of Kalam et al. suggests that GLPSS might be superior to LVEF in detecting myocardial dysfunction. The reason is explained by the limited ability of LVEF to assess systolic function in ventricular hypertrophy. For patients with hypertrophic cardiomyopathy, LVEF may be normal in presence of reduced systolic function. Another reason is the before mentioned location of the longitudinal fibers which is first affected by ischemia [7].
Changes of Longitudinal strain
The study of Gjesdal et al. demonstrated that GLPSS is able to distinguish non-infracted, transmural-infarcted and subendocardial-transmural-infarcted segments [2]. In terms of difference in GLPSS in patients with different myocardial infarction sites, no correlation was found in the study of Ismail et al [9].
13 Clinical application
Strain imaging is capable of identifying LV dysfunction earlier than conventional methods. It is starting to being applied in routine clinical diagnostics.
GLPSS by STE is recommended in adult patients who receive cancer therapy to detect sub-clinical LV dysfunction [7]. Chemotherapy has a toxic effect on the myocardium. Therefore, monitoring cardiac function is very important. This is generally carried out by measuring LVEF. However, reduction in myocardial strain precedes significant change in LVEF [13]. So it is recommended to measure LVEF prior to chemotherapy, at completion and six months after as well as measuring GLS in addition. This is useful when LVEF is in the normal lower range and it is difficult to conclude about systolic function [7].
Moreover, GLPSS is also being applied in assessing systolic function in patients with hypertrophic cardiomyopathy. As mentioned before the LVEF may be normal for patients with hypertrophic cardiomyopathy although the systolic function is reduced. That is why in current clinical practice guidelines for management of hypertrophic cardiomyopathy, the assessment of longitudinal strain in early disease is included [14].
Duration of early systolic lengthening
When there is a rise in pressure in the LV during early systole, myocardium that is affected by ischemia will tend to stretch before the onset of systolic shortening. This happens because of its reduced ability to generate active force. The time myocardial segments remain stretched is called duration of early systolic lengthening (DESL). This novel parameter might aid in identifying patients with suspected coronary artery disease. Smedsrud et al. demonstrated in their study that prolonged DESL in stable patients with suspected coronary artery disease was related to the presence of significant coronary artery stenoses. They suggest that DESL is superior to GLPSS in identifying patients with significant coronary artery disease [15]. The study of Zahid et al. showed that DESL could accurately identify non-STEMI patients without a visible scar on ceCMR. DESL provided incremental value over GLPSS and WMSI in identifying non-STEMI patients in that study. Moreover, DESL correlated well with infarct size and could distinguish patients with coronary occlusions and non-occlusions [16].
14 Changes of early systolic lengthening
The study of Smedsrud et al. demonstrated that in the follow-up echocardiography one year after revascularization the DESL was significantly reduced. No difference was detected between patients treated with PCI and the ones who underwent bypass surgery [15].
Zahid et al. also show that DESL was significantly shorter at follow-up echocardiography even before revascularization. Concerning DESL in the segments corresponding to the culprit artery, they found a tendency for it to be longer but without reaching statistical significance [16].
Biomarkers in LV remodeling
There are studies demonstrating that LV remodeling is associated with higher levels of cardiac troponin I, B-type natriuretic peptide (BNP) and C-reactive protein (CRP). It can suggest that LV remodeling is associated with a more extensive inflammatory process after AMI. Fertin et al. performed a systematic review of 59 publications examining the relation between different biomarkers and LV remodeling. They showed that natriuretic peptide were significantly associated with LV remodeling. Moreover, CRP and white blood cell counts were positively associated with LV remodeling in various studies [17].
Difficulties
It is important to keep in mind that there is no standardization of methodology between vendors of echocardiography models. Because of that, it is important that each echocardiography laboratory defines a normal range of strain values. It is also essential that a high degree of reproducibility is ensured [18].
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RESEARCH METHODOLOGY AND METHODS
We enrolled 54 patients who were hospitalized in Cardiology Department of Lithuanian University of Health Sciences because of the diagnosis of acute coronary syndrome (ACS) (first ST-segment elevation or first non-ST-ST-segment elevation myocardial infarction) between October 2009 and May 2011. Written informed consent was obtained from all patients and the protocol was approved by LSMU Bioethical Center, the ethics committee of the hospital.
Inclusion criteria
Inclusion criteria were: detection of rising of cardiac biomarker values (Troponin I) with at least one of the following criteria: 1) symptoms of ischemia; 2) new or presumably new significant ST-T changes or new left bundle branch block (LBBB); 3) development of pathological Q waves in the ECG; 4) imaging evidence of new loss of viable myocardium or new regional wall motion abnormality; 5) identification of an intracoronary thrombus by angiography or autopsy [19].
All patients underwent immediate coronary angiography and primary percutaneous coronary intervention (PCI) as indicated.
All of the patients were assigned to routine medical ACS treatment.
Exclusion criteria
Patients with following conditions were excluded: 1) prior MI or CABG (coronary artery bypass graft), 2) arrhythmias (non-sinus rhythm), 3) valvular diseases (rheumatic, congenital heart disease, prosthetic valves), 4) inadequate 2D echocardiographic images for analysis, 5) contraindication to coronary angiography.
Clinical data
The patients’ clinical records were reviewed for clinical and laboratory parameters: Cardiac risk factors were assessed which included cigarette smoking, diabetes mellitus, hypertension and hypercholesterolemia. A patient was categorized as a smoker when he had regularly smoked any cigarettes within 3 weeks before cardiac catheterization or was a past smoker. The classification for Diabetes mellitus included patients who required dietary treatment and/or medical therapy to control their blood glucose levels. The definition for hypercholesterolemia was set at a level of 5.2 mmol/L or
16 more of total serum cholesterol, more than 3.4 mmol/L of low-density cholesterol and 1.7mmol/L or more of triglycerides or the use of statin medication.
Echocardiography
Baseline echocardiography was performed on patients in the left lateral decubitus position within 48-72 hours after admission using 2D echocardiography. Follow-up echocardiography was performed after 3 months.
In all investigations, standard echocardiographic parameters and myocardial deformation characteristics under speckle-tracking echocardiography were measured. The parameters included LV volumes (end-systolic and end-diastolic), LVEF, wall motion score index (WMSI), mitral inflow peak early velocity (E)/mitral annular peak early velocity (E’), the E/E’ ratio. LVEDV, LVESV and LVEF were calculated from apical two- and four-chamber views by using the biplane Simpson’s technique. 2D STI analysis for evaluation of deformation parameters was performed.
Echocardiograms were performed using a commercially available system (Vivid Seven, General Electric-Vingmed Ultrasound AS, Horten, Norway). Standard images were obtained using a 3.5 MHz transducer at a depth of 16 cm in the parasternal and apical views.
The definition for LV remodeling was set as a ≥15% increase in LVEDV at 3-month follow-up compared to the baseline.
Speckle tracking
Speckle tracking from 2D grey-scale images was used to calculate strain. For longitudinal plane, three consecutive cycles were obtained and then stored for offline analysis. For the analysis of global LV strain commercially available software (EchoPac 6.1, GE Medical Systems, Horten, Norway) was used. The software divided each view of the LV into six segments (anteroseptal, anterior, lateral, posterior, inferior wall and interventricular septum). Segmental strain was calculated as an average strain within each segment. For each segment DESL and LPSS was recorded. DESL was defined as the time period in which the corresponding strain curve stayed positive from the onset of a Q-wave (or R-wave if Q was absent) (Figure 1). DESL in all six segments was averaged to obtain an average DESL value for each patient. LPSS values from all segments were averaged to acquire GLS.
17
Fig.1 Duration of early systolic lengthening by 2D speckle tracking echocardiography Strain curves from a patient with AMI after admission and 3 months later. DESL in ms.
Statistical Analyses
All data was analyzed in Microsoft Excel® and IBM SPSS Statistics® (SPSS software version 24, Chicago, IL, USA).
Data were presented as mean (¯) ± standard deviation (SD). The Student‘s t-test was used for testing hypothesis about equality of the means. For testing hypothesis of independence, the Chi-square test was used. Kruskal-Wallis test was used for non-parametric data. α = 0.05 was believed to be the significance level.
18 To predict LV remodeling after AMI in an individual patient longitudinal strain and early systolic shortening were further analyzed. Receiver operating characteristic (ROC) curve was applied. This optimum was defined as the value for which the sum of sensitivity and specificity was
19
RESULTS
Table 1
The clinical characteristics of the AMI patients without LV remodeling versus with LV remodeling
Clinical Data No LV Remodeling LV Remodeling P-Value
N 33 21 n.s.
Male 28 (84.8%) 17 (81,0%) n.s.
Female 5 (15.2%) 4 (19.0%) n.s.
Age 58.7±10.4 57.05±13.2 n.s.
IHD risk factors Arterial hypertension 29 (87.9%) 18 (85.7%) n.s. Diabetes mellitus 3 (9.1%) 2 (9.5%) n.s. Hyperlipidemia 25 (75.8%) 15 (71.4%) n.s. Obesity 23 (69.7%) 15 (71.4%) n.s. Smoking 23 (69.7%) 14 (66.7%) n.s. One-vessel disease 18 (54.5%) 11 (52.4%) n.s. Two-vessel disease 14 (42.4%) 8 (38.1%) n.s. Three-vessel disease 1 (3.0%) 2 (9.5%) n.s. Infarct-related artery Left anterior descending 12 (36.4%) 12 (57.1%) n.s. Left circumflex 9 (27.3%) 4 (19.0%) n.s. Right coronary 12 (36.4%) 5 (23.8%) n.s. Anterior MI location 11 (33.3%) 12 (57.1%) n.s. STEMI 27 (81.8%) 19 (90.5%) n.s. Angioplasty 32 (97.0%) 21 (100.0%) n.s. Stent placement 32 (97.0%) 21 (100.0%) n.s.
20 Troponin I (µg/mL) 7.9 (1.3; 21.6) 12.1 (1.9; 26.7) n.s
WBC (cells/L) 9.1±5.0 11.4±3.8 0.07
CRP (mg/L) 3 (1; 8) 8.5 (5; 17) 0.005
Table 2
Conventional echocardiographic parameters in AMI patient group with LV remodeling versus without LV remodeling at baseline and 3-month follow-up
No LV Remodeling (N=33) LV Remodeling (N=21)
Parameter Baseline Follow-up p-value Baseline Follow-up p-value LVEDD (mm) 48.6±5.2 49.3±6.0 n.s. 45.6±5.7 48.2±6.3 0.009 LVESD (mm) 32.8±5.2 33.9±6.9 0.0001 30.9±4.6 32.6±6.3 0.0001 LVEDV (mL) 83.1±20.1 81.2±20.8 n.s. 70.7±23.2 93.6±28.6 0.0001 LVESV (mL) 39.1±12.6 5.3±11.5 0.005 35.5±14.784 42.4±17.6 0.007 LVEF (%) 52±8.1 54.3±11.4 n.s. 51.5±9.7 48.9±12.1 n.s. WMSI 1.3±0.3 1.3±0.2 0.007 1.6±0.4 1.3±0.2 0.011 E/E’ 10.2±4.0 10.6±4.5 n.s. 11.7±6.0 10.2±4.4 n.s. E’ (m/sec) 6.3±2.0 6.8±2.3 n.s 7.0±2.1 7.6±2.6 n.s. LA diameter (mm) 39.1±4.3 40.6±4.2 0.060 36.2±4.7 39.2±5.5 n.s.
21 Table 3
Baseline strain imaging parameters in AMI patients without remodeling versus with remodeling
Parameter No LV Remodeling
(N=33)
LV Remodeling
(N=21) p-value
Global longitudinal peak
systolic strain -12.6±4.3 -10.2±3.4 0.038
Early systolic lengthening 70.3±22.0 109.7±47.2 0.001
When analyzing the speckle tracking parameters (Table 3) we found significant changes in GLPSS and DESL. When comparing the echocardiographic parameters (Table 2) between baseline and follow-up, we found p to be significant in several groups. In the patient group without LV remodeling there are changes in LVESD, LVESV, WMSI and LA diameter. The patient group with LV remodeling showed even more changes: LVEDD, LVESD, LVEDV, LVESV and WMSI changed from baseline to follow-up three months later. The only laboratory value that showed a significant change was CRP. CRP is significantly different between the patient group with and without remodeling (Table 1).
Fig.2 Receiver operating characteristics (ROC) curve testing the accuracy of global longitudinal
peak systolic strain and duration of early systolic lengthening to predict left ventricle remodeling (area under the curve 0.72, p=0.019)
22
DISCUSSION OF THE RESULTS
This study analyzed GLS and DESL in patients after AMI. The results of the comparison of the baseline values between the patient groups with and without remodeling showed that GLS and DESL have an important impact on LV remodeling.
Moreover, our results show that troponin I, leukocytes and C-reactive protein values are higher or have a tendency to be higher in the group with LV remodeling. This can suggest that LV remodeling is associated with a more extensive inflammatory process after AMI. Other authors also demonstrate that patients with LV remodeling had a higher level of white blood cells count and CRP. Fertin et al. performed a systematic review of 59 publications examining the relation between different biomarkers and LV remodeling. They showed that CRP and white blood cell counts were positively associated with LV remodeling in various studies [17]. The study of Žaliaduonytė-Pekšienė demonstrated that a higher white blood cell count at admission has an important impact in LV remodeling [20].
The parameters of conventional echocardiography indicate significant changes between the LV remodeling and non-LV remodeling group as well. LVEDD, LVESD, LVEDV and LVESV are remodeling predictors. However, according to the results of other researches, these parameters are not that sensitive to predict LV remodeling [11]. In our study, there is no significant change in EF between the two groups. This could be due to the relatively small study population. WMSI also showed significant change, it was increased in the LV remodeling group.
Our finding of GLS as a predictor of remodeling is supported by the results of other studies. The study of Hsiao et al. also investigated whether strain assessed by 2D STE could predict LV remodeling after AMI. The patient group was bigger than in our study, 83 AMI patients were included. 2D STE was performed on them immediately after admission like in our case and after a period of 6 months, 3 months later than we performed the follow-up examination. This cohort was divided into two groups depending on the presence or absence of LV remodeling as well. LV remodeling was defined as an increase of >15% in LVESV from the baseline. We defined it with the same value of LVESV. This study differs in the fact that focus was put on the patients with preserved EF (EF >40%). Univariate regression analyses were performed which revealed that segmental longitudinal strain > -15% (injury longitudinal strain (InjLS)) showed significant association with LV remodeling (p <0.01). This study proves that a longitudinal strain >-15% (InjLS) is an independent predictor for LV remodeling in patients with preserved EF [21].
Our result of GLS as a predictor of remodeling is additionally supported by the study of Žaliaduonytė-Pekšienė et al. who evaluated how feasible STE is in predicting LV remodeling after AMI. The focus was put on GLS. 2D STE was performed on 82 AMI patients 48-72 hours after onset
23 of AMI and at a 4-month follow-up. Our follow-up period was 3 months. The study defined LV remodeling as well as a 15% increase in LVEDV from the initial assessment to the follow-up. They also found that patients with LV remodeling at 4-month follow-up had a decreased baseline GLS (p < 0.05) (amongst other parameters) in comparison to the patients without LV remodeling. Multivariable logistic regression analysis was performed which showed GLS as an independent determinant of LV remodeling after AMI. A cutoff value of -11.6% for GLS was established to predict LV remodeling after a 4-month follow-up. This has a sensitivity of 78% and specificity of 73% of predicting LV remodeling in 4 months. This study reveals that GLS is an independent predictor of LV remodeling after AMI [20].
These data confirm that longitudinal function is sensitive to acute myocardial damage in patients after MI. It shows that GLS can predict clinical events.
Literature data on the prognostic value of DESL in LV remodeling prediction are scarce.
Smedsrud et al. demonstrated in their study that prolonged DESL in stable patients with suspected coronary artery disease was related to the presence of significant coronary artery stenoses. An average DESL value of 58 ms displayed optimal sensitivity and specificity for identification of significant coronary artery disease. In the follow-up echocardiography one year after revascularization the DESL was significantly reduced. There was no difference between patients treated with PCI and the ones who underwent bypass surgery. The study results suggest that DESL is superior to GLPSS in identifying patients with significant coronary artery disease. [15]. The study of Zahid et al. showed that DESL could accurately identify non-STEMI patients without visible scar on ceCMR. DESL was significantly shorter at follow-up echocardiography even before revascularization. Concerning DESL in the segments corresponding to the culprit artery, they found a tendency for it to be longer but without reaching statistical significance. The accuracy of DESL provided incremental value over GLPSS and WMSI in identifying non-STEMI patients in that study. The patients with no visible myocardial scarring had a DESL value of less than 50ms, which is the proposed cut-off value in that study. DESL correlated well with infarct size and could distinguish patients with coronary occlusions and non-occlusions [16]. Our data demonstrate that the area under the curve at ROC analysis is 0.72 (p=0.019), so we can confirm that DESL is a good and sensitive predictor of LV remodeling after acute MI.
24
CONCLUSIONS
1. Patients with left ventricle remodeling had higher C-reactive protein and a tendency to have a higher leukocyte level than patients without left ventricle remodeling.
2. Patients with left ventricle remodeling had decreased global longitudinal peak systolic strain and prolonged duration of early systolic lengthening suggesting that patients with following left ventricle remodeling have impaired left ventricle mechanic parameters just after the myocardial infarction while conventional echo parameters do not differ initially.
3. Novel parameters as global longitudinal peak systolic strain and especially duration of early systolic lengthening are sensitive parameters of left ventricle remodeling prediction.
25
PRACTICAL RECOMMENDATIONS
Strain imaging is capable of identifying LV dysfunction earlier than conventional methods. This has been proven by many studies. GLPSS is starting to being applied in routine clinical diagnostics. The use of GLPSS and DELS in clinical diagnostics should be increased.
26
LITERATURE LIST
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tomography perfusion imaging for nonviable myocardium identification. Biomedical Papers Med Fac Univ Palacky Olomouc Czech Repub. 2013;157(1):12-21.
2. Gjesdal, Ola, et al. Global longitudinal strain measured by two-dimensional speckle tracking echocardiography is closely related to myocardial infarct size in chronic ischaemic heart disease.
Clinical Science (Lond). 2007;113(6):287-96.
3. Mistry N, Beitnes JO, Halvorsen S, Abdelnoor M, Hoffmann P, Kjeldsen SE, et al. Assessment of left ventricular function in ST-elevation myocardial infarction by global longitudinal strain: a
comparison with ejection fraction, infarct size, and wall motion score index measured by non-invasive imaging modalities. Eur J Echocardiogr. 2011;12(9):678-83.
4. Bansal M, Kasliwal RR. How do I do it? Speckle-tracking echocardiography. Indian Heart J. 2013;65(1):117-23.
5. Westholm C JJ, Jernberg T, Winter R. The prognostic value of mechanical left ventricular dyssynchrony in patients with acute coronary syndrome. Cardiovascular Ultrasound. 2013;11(35).
6. Biere L, Donal E, Terrien G, Kervio G, Willoteaux S, Furber A, et al. Longitudinal strain is a marker of microvascular obstruction and infarct size in patients with acute ST-segment elevation myocardial infarction. PLoS One. 2014;9(1):e86959.
7. Smiseth OA, Torp H, Opdahl A, Haugaa KH, Urheim S. Myocardial strain imaging: how useful is it in clinical decision making? Eur Heart J. 2016;37(15):1196-207.
8. Abduch MCD, Alencar AM, Mathias Jr W, Vieira MLdC. Cardiac Mechanics Evaluated by Speckle Tracking Echocardiography. Arquivos Brasileiros de Cardiologia. 2014.
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