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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 18  |  Issue : 2  |  Page : 118-125

Role of 2D speckle-tracking echocardiography in the assessment of left atrial function and its relation to the presence of left atrial appendage thrombus in patients with non-valvular paroxysmal atrial fibrillation


Department of Cardiology, Faculty of Medicine (for Girls), Al-Azhar University, Cairo, Egypt

Date of Submission19-Jan-2020
Date of Decision19-Feb-2020
Date of Acceptance17-Mar-2020
Date of Web Publication24-Jul-2020

Correspondence Address:
MD Ola H Abd Elaziz
Lecturer of Cardiology, Faculty of Medicine for Girls, Al-Azhar University, 29 El Horya Street, Hadayek El Maadi, Cairo 11728
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AZMJ.AZMJ_8_20

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  Abstract 


Introduction The study aimed to evaluate the role of speckle-tracking echocardiography (STE) in the assessment of left atrial (LA) function and its relation to the presence of left atrial appendage thrombus (LAAT) compared with the gold standard transesophageal echocardiography (TEE) among patients with nonvalvular paroxysmal atrial fibrillation (AF).
Patients and methods Forty five patients with nonvalvular paroxysmal AF were included in the study. All patients underwent transthoracic echocardiography (TTE) immediately prior to or following clinically indicated TEE. LA deformation parameters such as left atrial global longitudinal strain-reservoir (LAGLS-RES), left atrial global longitudinal strain pump (LAGLS-pump), left atrial strain rate systolic (LA SR S), left atrial strain rate emptying (LA SR E), and left atrial strain rate atrial (LA SR A) were measured using 2D-STE. Through TEE, we assessed the presence of LAAT, left atrial appendage ejection fraction (LAA EF), left atrial appendage emptying (LAA E), and left atrial appendage filling (LAA F) velocities. Patients were divided into two groups according to the presence of LAAT.
Results LAAT was detected in 14 (31%) patients of our study population. STE-derived LAGLS-RES, LAGLS-pump, and LA SR A values were found to be significantly lower in patients with LAAT. There was positive correlation between LAA E velocity and LAGLS-RES, LAGLS-pump, LA SR S, and LA SR A (r=0.358, P<0.02; r=0.433, P<0.002; r=0.378, P<0.01; and r=0.390, P<0.01, respectively). The area under the receiver operating characteristic curve of LAGLS-RES, LAGLS-Pump, and LA SR A to discriminate patients with LAAT from those without LAAT was 0.74, 0.73, and 0.79, respectively. From all variables examined in the study LASRA was the strongest variable associated with the presence of LAAT.
Conclusion 2-D STE can be used for the assessment of LA mechanical function and discriminate patients with LAAT from those without LAAT compared with the gold standard TEE among patients with non-valvular paroxysmal AF.

Keywords: 2D speckle-tracking echocardiography, non-valvular atrial fibrillation, left atrial appendage thrombus, left atrial function, transesophageal echocardiography


How to cite this article:
Abd Elaziz OH, Abdel Hady BM. Role of 2D speckle-tracking echocardiography in the assessment of left atrial function and its relation to the presence of left atrial appendage thrombus in patients with non-valvular paroxysmal atrial fibrillation. Al-Azhar Assiut Med J 2020;18:118-25

How to cite this URL:
Abd Elaziz OH, Abdel Hady BM. Role of 2D speckle-tracking echocardiography in the assessment of left atrial function and its relation to the presence of left atrial appendage thrombus in patients with non-valvular paroxysmal atrial fibrillation. Al-Azhar Assiut Med J [serial online] 2020 [cited 2020 Oct 20];18:118-25. Available from: http://www.azmj.eg.net/text.asp?2020/18/2/118/290609




  Introduction Top


Atrial fibrillation (AF) constitutes the most common sustained arrhythmia. It affects 1–2% of the general population and is associated with many complications that alter the quality of life as the development of heart failure symptoms and the risk of thromboembolic events, including stroke or transient ischemic attack [1].

At present, the prevailing paradigm is that the risk of stroke in AF patients is independent of patient classification into paroxysmal AF and nonparoxysmal forms of AF [2].

Structural atrial remodeling in AF is represented by a decrease in myocardial velocities, lower compliance, altered strain and strain rate, lower emptying fraction, and cavity dilatation [3]. The impaired atrial contractile function during AF leads to lower blood flow velocity and favors the development of thrombi. Most commonly, thrombi develop in LA appendage (LAA) [4].

The gold standard tool for eliciting flow stasis, spontaneous echo contrast, and LAAT is transesophageal echocardiography (TEE), a semi-invasive method [5]. However, the routine application of semi-invasive TEE in such conditions may be limited by the risk of esophageal trauma or aspiration, the need for sedation, and patients’ discomfort [6].

Speckle-tracking echocardiography (STE) is a TTE technique that utilizes standard B-mode images for the assessment of myocardial deformation. It was first used for the evaluation of LV function. However, its application has extended to involve studying LA function as well [7].

Evaluation of LA strain by STE may represent a fast and easy-to-perform technique to assess LA function, due to its semiautomated and angle-independent nature and due to its off-line processing [7]; however, there are a relatively small number of studies validating this novel technique against a gold standard. Moreover, given the relative lack of experience using speckle-tracking on the left atrium, its effective role in clinical practice remains to be evaluated [8].


  Aim Top


The primary objective of this study was to evaluate the role of 2-D STE as a novel noninvasive technique in the assessment of LA function and its association with the presence of LAA thrombus in patients with nonvalvular paroxysmal AF.


  Patients and methods Top


The study cohort comprised 45 consecutive patients who were referred to the Cardiology Department of Al-Zahraa University Hospital for TEE because of different clinical indications in the period from August 2018 to August 2019.

Inclusion criteria

Patients with non-valvular paroxysmal AF were included in the study:
  1. Paroxysmal AF was defined as recurrent AF (≥two episodes) that terminated spontaneously within 7 days or episodes of AF of less than or equal to 48 h’ duration that were terminated with electrical or pharmacological cardioversion [9].
  2. All included patients were in sinus rhythm at the time of examination.


Exclusion criteria

Patients with valvular heart disease, valvular prosthesis, significant mitral regurgitation, and patients with contraindications for TEE were excluded from the study.

Written informed consent was taken from all participants before enrollment into the study and the study was approved by the Ethics Committee of Faculty of Medicine for Girls, Al-Azhar University.

All included patients were subjected to the following:
  1. Full medical history analysis and clinical examination.
  2. Routine laboratory investigations.
  3. Routine 12-lead ECG.
  4. Echocardiographic examination: echocardiography was performed in the fasting state with transthoracic and transesophageal examinations performed in immediate succession using GE Vivid E9 Ultrasound Machine (Horten, Norway).


Transthoracic echocardiography

All patients underwent an echocardiographic examination in the left lateral position, using Matrix probe M5s multifrequency 2.5 MHz, with the capability of tissue Doppler imaging and gray-scale recording for speckle-tracking study. Heart rate was continuously monitored during the transthoracic examination. All data were transferred to a workstation for further off-line analysis (GE EchoPAC for PC version 210 software, Horten, Norway). All measurements and evaluation were performed according to the guidelines of the American Society of Echocardiography [10].

  1. Conventional Echo Doppler assessment:
    1. *M-mode study:
        Left ventricular (LV) diameters and ejection fraction (EF) were measured.
        Left atrial (LA) diameters (medial–lateral and superior–inferior diameters) were also measured.


    2. *2-D study:
        Biplane 2-D echo LV volumes and EF were estimated from the apical four-chamber and two-chamber views using the biplane Simpson method.
        Left atrial volume index (LAVI) was estimated using the modified biplane area–length method and was corrected for body surface area.
    3. *Doppler study:
        Transmitral flow velocities (E and A) were estimated by pulsed-wave Doppler in the apical four-chamber (4C) view. The ratio of E/A velocity was measured.
        Tissue Doppler imaging was used to measure mitral annular velocities. The early diastolic velocity (Em) was obtained in the mitral septal, lateral, inferior, and anterior annulus and then averaged. E/Em ratio was calculated using the average Em. All Doppler measurements were obtained as the average values of three consecutive cardiac cycles.
  2. 2-D STE: two-dimensional echocardiographic images of the left atrium (LA) were obtained from the apical 4C and apical 2C views. All images were stored in a cine loop format from three consecutive beats. The frame rate for images was adjusted between 60 and 90 frames/s. All data were transferred to a workstation for further offline analysis (EchoPAC PC, GE version 210).


After defining the endocardial border manually, tracing was developed by the software automatically for each view. If the automatically obtained tracking segments were adequate for analysis, the software was allowed to read the data, whereas analytically inadequate tracking segments were either corrected manually or excluded from the analysis.

QRS-timed analysis was performed to obtain:
  1. LA peak strain just before mitral valve opening: It was taken as LA reservoir (LAGLS-RES), which was recorded as the average of the peak values from the apical four- and two-chamber views ([Figure 1]).
    Figure 1 Speckle-tracking strain analysis of the left atrium demonstrating left atrial global longitudinal strain-reservoir and left atrial global longitudinal strain-pump.

    Click here to view
  2. LA strain just before atrial contraction (onset of the P-wave on electrocardiography) was taken as LAGLS-PUMP ([Figure 1]).
  3. LA strain rate during ventricular systole (LA SR S): was taken as a reservoir strain rate and was measured as the peak positive value of strain rate within the first third of the cardiac cycle following QRS onset ([Figure 2]).
    Figure 2 Speckle-tracking strain rate analysis of the left atrium demonstrating left atrial strain rate during ventricular systole, left atrial strain rate emptying during ventricular passive filling, and left atrial strain rate atrial during active atrial contraction.

    Click here to view
  4. LA strain rate during passive ventricular filling (LA SR E): was taken as a conduit strain rate and was measured as the most negative strain rate value immediately following the positive reservoir strain rate deflection, typically in the middle third of the cardiac cycle ([Figure 2]).
  5. LA strain rate during active atrial contraction (LA SR A): was taken as an atrial contractile strain rate and was measured as the most negative strain rate in the last third of the cardiac cycle occurring between the electrocardiographic P-wave and the subsequent QRS complex ([Figure 2]).


Transesophageal echocardiography

Following topical pharyngeal anaesthesia and intravenous sedation, the transesophageal probe (6Tc-RS probe) was positioned at the mid-esophageal level for the measurement of left atrial appendage emptying velocity (LAA E).

The probe was angulated to permit the most parallel alignment for pulse-wave Doppler echocardiography with the LA appendage long axis, and the sample volume was positioned 1 cm into the ostium of the appendage. Two-dimensional gray-scale imaging of the LA cavity was performed with gain settings optimized. All data were stored digitally for off-line analysis.

Measurement of left atrial appendage emptying velocity (LAA E) was averaged over three consecutive cardiac cycles. For the evaluation of the presence of LAA thrombus, gain settings were standardized as previously described. LAA thrombus was defined as a soft echodensity with a discrete border seen in multiple views within LAA ([Figure 3]).
Figure 3 Transesophageal echocardiography mid-esophageal view with PW Doppler shows left atrial appendage emptying velocity and left atrial appendage filling velocity.

Click here to view


Statistical analysis of data

Numerical variable was expressed as mean and SD. The following statistical tests were used for analysis of data by SPSS version 16 Inc., Armonk, New York, USA:
  1. Independent t-test for testing statistically significant difference between the means of two groups in each classification.
  2. Pearson’s correlation test with the determination of correlation coefficient (r) to test a positive or negative relationship between two variables.
  3. Receiver operating characteristic curve analysis: to determine the optimal cutoff value, sensitivity, and specificity of STE-derived parameters of LA deformation in discriminating patients with LAAT from those without LAAT.
  4. Binary logistic regression analysis to determine the strongest LA deformation parameter which is associated with the presence of LAAT.


P value less than 0.05 was considered statistically significant.


  Results Top


The study included 45 patients with nonvalvular paroxysmal AF. They were 29 (64%) women and 16 (36%) men. The mean age of the patients was 56±7.9 years. The baseline demographic and clinical data of all the studied population are shown in [Table 1].
Table 1 Demographic and clinical data of the study population

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The study populations were divided into two groups according to the presence of LAA thrombus:
  1. Group I: included 14 (31%) patients with LAA thrombus detected.
  2. Group II: included 31 (69%) patients with absent LAA thrombus.


Comparison between groups I and II as regards transthoracic echocardiographic evaluation

The study revealed significant decrease of LV systolic function as measured by TDI (average Sm) in group I compared with group II and significant increase of LA superior–inferior diameter among group I compared with group II, while there was no significant difference between the two groups as regards other examined parameters as shown in [Table 2].
Table 2 Comparison between the two studied groups as regards transthoracic echocardiography parameters

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Comparison between groups I and II as regards LA deformation parameters measured by speckle-tracking echocardiography

The study showed significant decrease of LAGLS-RES, LAGLS-pump, and LA SR A in group I compared with group II; however, there was no statistically significant difference between the two groups as regards LA SR S, and LA SR E as shown in [Table 3].
Table 3 Comparison between the two groups as regards speckle-tracking echocardiography left atrial deformation parameters

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Comparison between groups I and II as regards TEE parameters

The study showed significant decrease of LAA EF and LAA E velocity in group I compared with group II, while there was decrease of LAA F in group I compared with group II; however, it did not reach statistically significant difference as shown in [Table 4] and [Table 5].
Table 4 Comparison between the two groups as regards transthoracic echocardiography parameters

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Table 5 Correlation between average left atrial appendage emptying velocity and left atrial deformation parameters measured by speckle-tracking echocardiography

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Correlation between TEE LAA-E velocity and LA deformation parameters measured by speckle-tracking echocardiography

The study showed weak positive correlation between LAA-E velocity and LAGLS-RES, LAGLS-pump, LA SR S, and LA SR A.

Binary logistic regression analysis with enter model was performed to detect the strongest parameter that was associated with the presence of LA thrombus among LAGLS-RES, LAGLS-pump, LA SR S, LA SR E, LA SR A, and LAA E. It showed that LA SR A was the strongest parameter associated with the presence of left atrial thrombus.

Receiver operating characteristic curve analysis was used to determine the cutoff value, sensitivity, specificity, and area under the curve of LAGLS-RES, LAGLS-pump, and LA SR A in discriminating patients with LAAT from those without LAAT as shown in [Table 6] and [Figure 4].
Table 6 Best cutoff values, sensitivity, specificity, and area under the curve of the speckle-tracking echocardiography-derived parameters of LA deformation

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Figure 4 Receiver operating characteristic curve of left atrial strain rate atrial in relation to the presence of left atrial appendage thrombus, with sensitivity and specificity values.

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  Discussion Top


Thromboembolism is the most common complication in patients with non-valvular AF. Ischemic stroke is about as common in paroxysmal AF as in permanent AF, and about twice as common as in the general population [11]. While TEE is the gold standard technique to detect LAAT, this modality is semi-invasive and may not be suitable to all patients. Recent studies have reported the successful use of noninvasive approaches to diagnose LAAT, including two-dimensional STE-based measurement of LA parameters [7].

This study was designed mainly to explore the role of parameters of LA deformation derived by STE in the assessment of LA function and their association with the presence of LAAT among patients with nonvalvular paroxysmal AF.

LAA thrombus was detected in 31% of our study population using the gold standard TEE technique. This high incidence of LAA thrombosis among our study population may be due to our study design which excluded patients with significant mitral regurgitation from the study. Mitral regurgitation was reported to have a protective effect against thrombus formation [12]. In addition, most of our study population was not properly adherent to anticoagulants; however, this issue was not crucial in their recruitment into the study.

There was no significant difference between subgroups with and without LAA thrombus as regards conventional TTE parameters such as LV EF, LAV index, E velocity, A velocity, average Em, and E/Em ratio. This result is consistent with the result of Leong et al. [8], who studied the relationship between novel 2-D TTE indices of LA mechanical function (STE-derived and TDI-derived parameters), conventional indices and TEE parameters in the assessment of LA function and prediction of LAAT, and found that STE-derived parameters were more predictive and tended to exhibit superior technical feasibility.

However, this result is discordant to the results of Doukky et al. [13], who reported that LV EF and LAV index were independent predictors of LAAT in patients with non-valvular AF. Also, this result is discordant with the result of Doukky et al. [14], who reported that diastolic function indices E/Em and average Em velocity were independently associated with LAAT in non-valvular AF.

In our study, the subgroup without LAAT had significantly higher strain and strain rate values. These parameters have also been shown in previous studies to be predictive of reverse remodeling and identifying responders to cardioversion and ablation [15].

Among the STE-derived parameters of LA strain, our study showed significant reduction of LAGLS-RES, LAGLS-pump, and LA SR A in the subgroup with LAAT compared with that without LAAT. This result is consistent with the results of Kupczynska et al. [16], who studied also the association between LA function assessed by STE and the presence of LAAT in patients with AF and reported a significant reduction of parameters of LA global strain and strain rate among the LAAT group; however, they did not measure LA SR A among their patients.

There was significant reduction of TEE-derived LAA EF and LAA E velocity among the subgroup with LAAT in our study. This result is consistent with previous studies [8],[16],[17].

TEE-pulsed Doppler measurement of LAA flow velocities has been shown to predict thromboembolic risk. Specifically, LAA E velocity has been extensively validated in many studies to be one of the gold standard predictors of LAAT in AF [18]. Our study showed weak positive correlation between LAA-E velocity and STE-derived parameters of LA deformation (LAGLS-RES, LAGLS-pump, LA SR S, and LA SR A). This is consistent with previous studies [8],[16],[17].Among all STE-derived parameters of LA deformation examined in our study, binary logistic regression analysis demonstrated LA contractile strain rate (LA SR A) as the strongest parameter associated with LAA thrombus presence. To the best of our knowledge, this study is the first to demonstrate such a result. This deserves further verification in more studies including a larger sample size.

The area under the curve of STE-derived LAGLS-RES, LAGLS-pump, and LA SR A to detect LAAT in our study was 0.74, 0.73, and 0.79, respectively, with sensitivity and specificity values comparable to those reported in previous studies [8],[16],[17].

Study limitations

Our study has some limitations. This is a single-center study, with a relatively small group of patients. Therefore, the results need to be validated in larger prospective studies. The study did not have a matching control group of healthy individuals because TEE could not be performed ethically in the control group. Another limitation, we did not consider in our study, design calculation of CHA2DS2-VASc score which is approved as an important predictor of thromboembolic risk in patients with nonvalvular AF. Also, no data may be inferred regarding the potential impact of anticoagulation therapy since the patients were recruited to the study regardless of the anticoagulation regimen.


  Conclusion Top


Assessment of LA mechanical function using STE is a valid approach compared with transesophageal echocardiography, and is clinically feasible in discriminating patients with LAAT from those without LAAT among patients with nonvalvular paroxysmal AF.

Recommendations

  1. Evaluation of LAA function in patients with paroxysmal AF can be performed using either the gold standard TEE or the noninvasive STE approaches.
  2. The role of STE in the assessment of LA function and prediction of LAAT among patients with paroxysmal AF needs further evaluation in larger prospective randomized studies including a larger sample size and longer periods of follow-up.


Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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1.
Camm AJ, Kirchhof P, Lip GY, Schotten U, Savelieva I, Ernst S et al. Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC). Eur Heart J 2010; 31:2369–2429.  Back to cited text no. 1
    
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Uretsky S, Shah A, Bangalore S, Rosenberg L, Sarji R, Cantales DR et al. Assessment of left atrial appendage function with transthoracic tissue Doppler echocardiography. Eur J Echocardiogr 2009; 10:363–371.  Back to cited text no. 4
    
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Calkines H, Kuck KH, Cappato R, Brugada J, Camm AJ, Chen SA et al. HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: recommendation for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design. Europace 2012; 14:528–606.  Back to cited text no. 9
    
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Doukky R, Khandelwal A, Garcia-Sayan E, Gage H. External validation of a novel transthoracic echocardiographic tool in predicting left atrial appendage thrombus formation in patients with nonvalvular atrial fibrillation. Eur Heart J 2013; 14:876–881.  Back to cited text no. 13
    
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Kupczynska K, Michalski BW, Miskowiec D, Kasprzak JD, Wejner-Mik P, Wdowiak-Okrojek K et al. Association between left atrial function assessed by speckle-tracking echocardiography and the presence of left atrial appendage thrombus in patients with atrial fibrillation. Anatol J Cardiol 2017; 18:15–22.  Back to cited text no. 16
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

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