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ORIGINAL ARTICLE
Year : 2014  |  Volume : 27  |  Issue : 4  |  Page : 699-704

The association between left atrial strain and the CHA 2 DS 2 -VASc risk score in patients with atrial fibrillation


1 Cardiology Department, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Kwisna Hospital, Menoufia, Egypt

Date of Submission09-Feb-2014
Date of Acceptance20-Apr-2014
Date of Web Publication22-Jan-2015

Correspondence Address:
Mofeed Ahmad Nasif
Berket El Sabaa
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.149700

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  Abstract 

Objective
The aim of this work was to study the relationship between echocardiographic parameters and the CHA 2 DS 2 -VASc score in patients with nonvalvular atrial fibrillation (AF).
Background
Strain and strain rate imaging using two-dimensional speckle-tracking echocardiography is a new modality that has emerged recently to estimate myocardial function accurately. Left atrial (LA) strain analysis is a new tool that can be used to evaluate LA function. LA strain may correlate with the CHA 2 DS 2 -VASc score.
Patients and methods
We prospectively identified 30 patients with AF, and 20 normal individuals served as controls. All 50 participants underwent standard two-dimensional Doppler and speckle-tracking echocardiography.
Results
The LA diameter was greater in patients with AF when compared with the control group (5.03 ± 0.85 vs. 3.30 ± 0.57, P < 0.001). The peak LA longitudinal strain in both the apical four-chamber (AP4) and the apical two-chamber (AP2) views was reduced in patients with AF when compared with controls (12.42 ± 7.17 vs. 49.89 ± 8.45 in the AP4 view and 11.85 ± 7.32 vs. 49.17 ± 7.97 in AP2, P < 0.001), and it was negatively correlated with the CHA 2 DS 2 -VASc score, but without statistical significance (P > 0.05).
Conclusion
LA strain, which is a marker of dynamic LA function, is significantly reduced in AF patients. The correlation between the peak LA strain and the CHA 2 DS 2 -VASc score was negative, but it did not reach statistical significance.

Keywords: Atrial fibrillation, left atrial strain, speckle-tracking echocardiography


How to cite this article:
Abd-Elaziz WF, Ahmad MK, Nasif MA. The association between left atrial strain and the CHA 2 DS 2 -VASc risk score in patients with atrial fibrillation. Menoufia Med J 2014;27:699-704

How to cite this URL:
Abd-Elaziz WF, Ahmad MK, Nasif MA. The association between left atrial strain and the CHA 2 DS 2 -VASc risk score in patients with atrial fibrillation. Menoufia Med J [serial online] 2014 [cited 2020 Feb 26];27:699-704. Available from: http://www.mmj.eg.net/text.asp?2014/27/4/699/149700


  Introduction Top


Atrial fibrillation (AF) is the most common sustained arrhythmia in the general population; its prevalence increases with age and is generally associated with increased mortality [1].

Patients with AF have a substantial risk of stroke, which is modified by the presence or the absence of several risk factors [2].

Since 2006, stronger evidence has accumulated that there are additional risk factors that should be considered in assessing the thromboembolic risk and would be of value in identifying those patients at truly low risk [3]. The additional risk factors have been expressed in the CHA 2 DS 2 -VASc (congestive heart failure, hypertension, age³75 years, diabetes mellitus, previous stroke/transient ischemic attack, vascular disease, age 65-74 years, sex category, age³75 years, and previous stroke carry doubled risk weight) score, which has been proposed to complement the CHADS 2 score (3) .

During the past several years, strain and strain rate imaging have emerged as a quantitative technique to estimate myocardial function and contractility accurately. Non-Doppler, two-dimensional strain imaging is a new echocardiographic technique for obtaining strain and strain rate measurements. It analyzes motion by tracking speckles in the ultrasonic image in two dimensions [4].

The analysis of left atrial (LA) strain is a new tool that can be used to evaluate LA function [5].

We aimed in this study to assess LA function using two-dimensional speckle-tracking echocardiography (2D STE) and to study its correlation with the CHA 2 DS 2 -VASc score.


  Patients and methods Top


The study was performed prospectively in the period between June 2012 and October 2013 on 30 patients with nonvalvular AF referred to the Cardiology Department, Menoufia University Hospital, who were compared with 20 control patients in sinus rhythm with their age and sex matching with group 1. Comorbid conditions such as diabetes, hypertension, heart failure, a history of stroke and vascular diseases, including coronary artery disease, heart attack (myocardial infarction), peripheral artery disease, and complex aortic plaque were taken into account to risk-stratify the participants according to CHA 2 DS 2 -VASc criteria. Patients with primary valvular heart disease, congenital heart diseases, primary myocardial diseases, pericardial diseases, a resting heart rate greater than 100 beats/min and any arrhythmia other than AF, poor echogenic patients, and patients refusing to participate in the study were excluded.

All patients underwent physical examination and a 12-lead ECG routine echocardiographic study. Two-dimensional echocardiography and Doppler examination were performed with a GE Vivid 9 Ultrasound Machine (Echo Pac; GE Vingmed, Horten, Norway) with a multifrequency 1.7-4-MHz transducer of the 'M S5' type and conducted to a single-lead ECG. All examinations were performed with the patients in the standard left lateral position. LA and left ventricular (LV) measurements were taken using the two-dimensionally guided M-mode. A two-dimensional echocardiographic study was used to assess wall motion for any abnormalities, valves, the pericardial sac, and any congenital heart disease.

For speckle-tracking analysis of the LA chamber, apical four-chamber and two-chamber view images were obtained using conventional two-dimensional gray-scale echocardiography, during breath hold, with a stable ECG recording.

Particular attention was given to obtain an adequate gray-scale image, allowing reliable delineation of the myocardial tissue and extracardiac structures. Three consecutive heart cycles were recorded and averaged. The frame rate was set between 60 and 80 frames/s or at least 40% of the heart rate; these settings are recommended to enhance the feasibility of the frame-to-frame tracking technique. Recordings were processed using an acoustic-tracking software incorporated in the Vivid Nine system (Echo Pac; GE Vingmed), allowing offline semiautomated analysis of speckle-based strain.

To calculate LA strain, the atrial endocardium was first traced manually. The epicardial surface was calculated automatically, and after manually reducing the region of interest to the atrial thickness, the software automatically divided each wall of the apical four-chamber 'septal and lateral wall' and two-chamber 'anterior and inferior wall' views into three segments: the apical, the mid, and the basal segments; we took the average of this wall and the average of the view, and repeated these steps in each wall of both apical four-chamber and two-chamber views because there is still no software available to calculate the atrial strain; we used the same software that is used for the analysis of ventricular function, and once the longitudinal atrial strain curves were obtained, measurement of the peak atrial strain was taken (which was plotted as a peak of the positive curve).

Statistical analysis

Using the statistical package for the social science software (SPSS) version 16, data from patients and controls were collected and subjected to statistical analysis.

The unpaired t-test was used to compare quantitative variables in two independent groups of parametric data (SD <50% of the mean). The Mann-Whitney U-test was used to compare quantitative variables in two independent groups of nonparametric data.

The level of significance was 95%. Hence, P-value greater than 0.05 was considered as a nonsignificant result, P-value less than 0.05 was considered as a significant result, and P-value less than 0.001 was considered as a highly significant result [6].


  Results Top


This study included 30 AF patients (14 male and 16 female, with a mean age of 65.03 ± 8.53 years) and 20 individuals as the control group (10 male and 10 female, with a mean age of 60.8 ± 6 years).

On comparing conventional echocardiographic measurements in the studied groups, there was a highly statistically significant reduction in group 1 (patients with AF) regarding ejection fraction (EF) and fractional shortening (FS), whereas there was a statistically significant increase in left ventricular end-diastolic (LVED) (P < 0.05) and a highly statistically significant increase in group 1 regarding left ventricular end-systolic (LVES) (P < 0.001) when compared with the control group. However, no difference regarding interventricular septum in diastole, interventricular septum in systole, LV posterior wall in diastole, and the aortic diameter diameter was found (P > 0.05).

The LA diameter showed a highly statistically significant increase in the patient group compared with the control group (5.03 ± 0.85 vs. 3.30 ± 0.57, P < 0.001). Also, the LA volume in both views showed a highly statistically significant increase in the patient group (P < 0.001) compared with the control group.

By STE, values of the peak LA longitudinal strain in both the AP4 and the AP2 views were highly statistically significantly reduced in group 1 (patients with AF) when compared with the control group (12.42 ± 7.17 vs. 49.89 ± 8.45 in the AP4 view and 11.85 ± 7.32 vs. 49.17 ± 7.97 in AP2, P < 0.001) as shown in [Table 1]. When values of the peak LA strain correlated with the CHA 2 DS 2 -VASc score, there was a negative correlation, but it did not reach statistical significance (P > 0.05) as shown in [Table 2] and [Table 3]. The correlation between the CHA 2 DS 2 -VASc score and LA dimensions in the patient group was positive, but it did not reach statistical significance (P > 0.05) as shown in [Table 4].
Table 1: Comparison of the mean of the peak left atrial strain of each wall and the mean of each view in the studied groups

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Table 2: Pearson's correlation between the score and the mean of the peak left atrial strain of each wall in the patient group

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Table 3: Pearson's correlation between the score and the mean of the peak left atrial strain of each view in the patient group

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Table 4: Pearson's correlation between the score and left atrial dimensions in the patient group

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  Discussion Top


AF is the most common cardiac arrhythmia; it affects nearly 1% of the population [2], and is now recognized as the most common cardiac disorder leading to stroke and other thromboembolic events [7]. The risk of stroke in AF patients is modified by the presence or the absence of several risk factors [2]. The CHADS 2 score does not include some common stroke risk factors [8]. To complement the CHADS 2 score, by the inclusion of additional 'stroke risk modifier' risk factors, the CHA 2 DS 2 -VASc score has been proposed [3]. The CHA 2 DS 2 -VASc score has been used in the new European Society of Cardiology guidelines for the management of AF [9]. STE is a two-dimensional, strain, non-Doppler-based modality that has been used recently to evaluate dynamic LA function [10].

In this study, we assessed LA function by 2D STE in 30 patients with nonvalvular AF compared with 20 control patients who were age-matched and sex-matched to the AF group.

Regarding LA dimensions, the present study showed that AF patients had significantly larger LA dimensions than the control group by M-mode (LA diameter; [Table 5]) and tracing methods [Table 6]. These findings are in agreement with Mont et al. [11].
Table 5: Comparison between the two groups regarding their demographics data

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Table 6: Comparison between the two groups regarding the conventional echocardiographic data

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The higher LA dimensions in the AF group in this study can be explained as follows: first, the AF group included 11 patients with chronic heart failure (CHF), representing 36% of the patient group. In CHF with augmented stiffness or reduced compliance of the left ventricle, the LA pressure increases to preserve LV filling. As a result, the Frank-Starling mechanism begins to operate in the LA, leading to chamber dilation and increased contractility, systolic force, and work [12]. Rossi et al. [13] identified the degree of LV dilation, diastolic dysfunction, and the extent of mitral regurgitation as the variables independently related to the LA volume in a large group of patients with systolic CHF. Second, the AF group includes 25 patients with hypertension, representing 85% of the patients in this group. It is known that hypertension leads to an increase in LA dimensions as demonstrated by Milutinoviζ et al. [14], who found that the LA size was statistically greater in patients with arterial hypertension in relation to healthy individuals. The higher LA size in hypertensive patients can be explained by (a) the presence of diastolic impairment as demonstrated by Pavlopoulos and Nihoyannopoulos [15] who found that patients with global diastolic dysfunction had more deteriorated segmental relaxation (segmental diastolic dysfunction) and a higher LA size, and (b) the presence of associated mitral regurgitation, aging, LVH, and the concentric LV geometry as confirmed by Gerdts et al. [16], who found that LA enlargement was related to LV hypertrophy and an eccentric geometry, a higher BMI, systolic blood pressure, age, female sex, and mitral regurgitation (all, P < 0.05). Thus, the LA size in hypertensive patients with ECG LV hypertrophy is influenced by the sex, the age, obesity, the systolic blood pressure, the LV geometry, and the presence of mitral regurgitation. Also Cioffi and Stefenelli [12] found that a concentric LV geometry is associated with a greater LA size, and the degree of LA enlargement depends on the LV mass. Third, AF by itself can cause an increase in the LA size; this was demonstrated by Suarez et al. [17] as they found that chronic AF occurring in patients with structurally normal hearts (lone AF) may cause a slow and progressive increase in the LA size. The enlargement relates to the total duration of arrhythmia and is independent of changes in the LV size or function. This enlargement in the LA size can be attributed to structural remodeling as demonstrated by De Jong et al. [18], who stated that structural remodeling, including atrial dilatation, hypertrophy, fibrosis, dedifferentiation, apoptosis, and myolysis, are related to the severity of the underlying disease and the duration of AF.

Regarding the left ventricle conventional echocardiographic parameters in our study, there was a significant statistical difference between the two groups with respect to the LVED dimension, the LVES dimension, the EF, and FS [Table 5], wherein the LVED and the LVES were significantly larger in the AF group than in the control group; meanwhile, the LV systolic function assessed by EF and FS were significantly reduced in the AF group than in the control group. Rather than these parameters, there was no significant statistical difference between the two groups with respect to the conventional echocardiographic parameters of the other left ventricle.

Ling et al. [19] found that persistent AF patients had a lower EF than controls and paroxysmal AF patients. These findings are in agreement with our study.

The impairment of LV systolic function in AF patients can be attributed to tachycardia-induced heart failure as demonstrated by Umana et al. [20]; they found that 50% of the patients with AF and LV dysfunction have some degree of tachycardia-induced heart failure. Moreover, the prevalence of AF in patients with heart failure increased in parallel to the severity of the disease, ranging from 5% in patients with mild to 10-26% among patients with moderate and up to 50% in patients with severe heart failure as stated by Maisel and Stevenson [21].

Regarding the mean of the peak LA strain, the present study showed that AF patients had a significantly smaller peak LA strain than the control group by the speckle-tracking method [Table 7]. These findings are in agreement with Shaikh et al. [22].
Table 7: Comparison of the left atrial volume in the studied groups

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This impairment of LA function in AF patients is attributed to extensive abnormalities in the atrial ultrastructure in the form of an increase in the cell size, myolysis, and perinuclear accumulation of glycogen and increased interstitial fibrosis [23]. Hoit et al. [24] demonstrated that 6 weeks of rapid (400 beats/min) atrial pacing and a normal ventricular rate response produce an isolated atrial cardiomyopathy characterized by an impaired booster pump and reservoir functions and increased chamber stiffness and relative conduit function. The model mimics the effects of rapid atrial tachycardias, such as atrial flutter and fibrillation, independent of the ventricular function.

In the present study, the correlation between the CHA 2 DS 2 -VASc score and the peak LA strain was determined. There was a negative correlation, but it did not reach statistical significance [Table 1] and [Table 2]. These findings disagree with Islas et al. [25].

Current risk stratification schemes such as the CHADS 2 and the CHA 2 DS 2 -VASc scores are based on clinical risk factors and suboptimally weight the risk/benefit of anticoagulation [26]. These risk factors did not asses the LA contractility. Although quantification of LA myocardial function by speckle tracking has been proposed recently [5], AF by itself destroys LA function, and moreover, LA dysfunction occurs even in lone atrial fibrillation (LAF). This was proved by Hong et al. [27] who compared 45 paroxysmal LAF patients and 30 healthy control individuals in sinus rhythm regarding the longitudinal left atrial strain/strain rate of booster, reservoir, and conduit function by 2D STE. They found that left atrial strain and left atrial strain rate of the three phasic functions were reduced in patients, whereas the LA volume was similar in the two groups. They finally concluded that remodeling of the LA booster pump, the reservoir, and the conduit function in LAF patients can be detected by 2D STE before structural remodeling and the occurrence of LAF is associated with impairment of LA intrinsic myocardial properties. Azemi et al. [28] retrospectively studied patients with AF, stroke or transient ischemic attack, and CHADS 2 scores of 1 or less before their events from a large single-center stroke registry and compared it with age-matched and sex-matched controls regarding echocardiographic parameters including chamber volumes, the LV mass, the LA peak negative and positive strain, and the strain rate, and they demonstrated that the peak positive LA strain (14 ± 11 vs. 25 ± 12%, P < 0.001) was significantly reduced in patients compared with controls. Even if the CHADS 2 score was 0, the LA mean strain was reduced as demonstrated by Li et al. [29], who found that the LA mean strain was 18.33 ± 8.57 in the patient group of CHADS 2 score 0. However, Shih et al. [30] found that the LA peak longitudinal strain in patients with mean CHADS 2 score 2.0 ± 0.7 was 10.44 ± 4.23. In our study, the mean peak LA strain was 12.42 ± 7.17 in the AP4 view and 11.85 ± 7.32 in the AP2 view. From these results, we can conclude that the LA strain is reduced in patients with AF, but the difference in values is located in a narrow range despite the variations in their score [Figure 1].
Figure 1: The peak longitudinal strain of the three segments of the lateral wall of left atrial in the apical four-chamber view.

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  Conclusion Top


The LA strain, which is a marker of dynamic LA function, is significantly reduced in AF patients. The correlation between the peak LA strain and the CHA 2 DS 2 -VASc score was negative, but it did not reach statistical significance.


  Acknowledgements Top


Conflicts of interest

There are no conflicts of interest.

 
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    Figures

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]



 

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