Global Left Atrial Strain Correlates with CHADS 2Risk Score in Patients with Atrial Fibrillation


The aim of this cross-sectional study was to explore the association between echocardiographic parameters and CHADS 2 score in patients with nonvalvular atrial fibrillation (AF).


Seventy-seven subjects (36 patients with AF, 41 control subjects) underwent standard two-dimensional, Doppler, and speckle-tracking echocardiography to compute regional and global left atrial (LA) strain.


Global longitudinal LA strain was reduced in patients with AF compared with controls ( P < .001) and was a predictor of high risk for thromboembolism (CHADS 2 score ≥ 2; odds ratio, 0.86; P = .02). LA strain indexes showed good interobserver and intraobserver variability. In sequential Cox models, the prediction of hospitalization and/or death was improved by addition of global LA strain and indexed LA volume to CHADS 2 score ( P = .003).


LA strain is a reproducible marker of dynamic LA function and a predictor of stroke risk and cardiovascular outcomes in patients with AF.

Atrial fibrillation (AF) is one of the most common arrhythmias encountered in clinical practice, affecting >2.3 million adults in the United States. Between 1996 and 2001, hospitalization with AF as the first listed diagnosis increased by 34%. The majority of these patients also have associated cardiovascular disease; the most common causes of cardiovascular death reported were coronary artery disease, heart failure, and ischemic stroke. Notably, the risk for stroke is high irrespective of whether AF is paroxysmal, persistent, or permanent.

Typically, the CHADS 2 score, with a range of 0 to 6 points, has been used to risk-stratify patients with AF, by assigning 1 point each for the presence of congestive heart failure, hypertension, age ≥ 75 years, and diabetes mellitus and 2 points for history of stroke or transient ischemic attack. A CHADS 2 score ≥ 2 is associated with heart failure and higher levels of vascular events.

Although the CHADS 2 score is a valuable marker for prediction of cardiovascular events and stroke, the association between CHADS 2 score and echocardiographic parameters is incompletely understood. Speckle-tracking echocardiography is a two-dimensional (2D), strain, non-Doppler-based modality that has been used recently to evaluate dynamic left atrial (LA) function. The incremental value of measuring LA strain in patients with AF remains unclear. In this study, we determined the association of echocardiographic variables with CHADS 2 score in patients with AF. We further hypothesized that reduction of LA strain in patients with long-standing AF would parallel the CHADS 2 score and would have incremental value over LA size for predicting future adverse cardiovascular outcomes.


The study was approved by the Ethics Committee of Umeå University, Umeå, Sweden. All participants provided informed consent. Seventy-seven subjects attending Sundsvall Hospital in central Sweden between March and July 2009 were included in the study: 36 consecutive patients with nonvalvular AF and 41 nonconsecutive control subjects in sinus rhythm. All patients underwent routine echocardiographic study after initial treatment in the emergency department or in the cardiology department of the same hospital. Subjects with more than mild to moderate valve disease and primary myocardial and pericardial diseases were excluded. Comorbid conditions such as diabetes, hypertension, heart failure, and history of stroke were taken into account to risk-stratify the subjects according to CHADS 2 criteria.

Conventional Echocardiography

All participants underwent routine echocardiography (Philips iE33; Philips Medical Systems, Eindhoven, The Netherlands), and the images were postprocessed using Xcelera software (Philips Medical Systems). Standard 2D and Doppler echocardiographic measurements were determined in accordance with current American Society of Echocardiography guidelines. For the assessment of LA volume, orthogonal apical views, most commonly apical four-chamber and two-chamber views, were obtained to determine LA area and length (from the middle of the plane of the mitral annulus to the posterior wall). The apical long-axis view was then used instead of the two-chamber view if the left atrium in the latter view appeared foreshortened. Specifically, the maximal LA chamber area and length were measured at end ventricular systole, excluding the LA appendage and pulmonary veins. LA volume was calculated on the basis of the algorithm [(0.85 × A 1 × A 2)/ L ], where A 1 is the four-chamber LA area, A 2 is the two-chamber or apical long-axis LA area, and L is the average of the two lengths obtained from the orthogonal views and indexed to body surface area. Indexed LA diameter, four-chamber LA area, and indexed LA volume were categorized according to current American Society of Echocardiography guidelines. The LA emptying fraction was calculated from maximum and minimum volumes ([maximum volume − minimum volume]/maximum volume). Pulmonary artery systolic pressure was obtained using tricuspid regurgitation velocity, inferior vena cava diameter and its respiratory variation, and hepatic venous pulsed-wave Doppler. Left ventricular (LV) systolic function was assessed by atrioventricular plane excursion, and LV ejection fraction was assessed by a modified biplane Simpson’s method. Right ventricular mechanical function was measured by tricuspid annular plane systolic excursion. LV ejection fraction and LV filling pressure (by the ratio of mitral peak velocity of early filling to early diastolic mitral annular velocity, determined using the average early diastolic mitral annular velocities of the septal and lateral LV annulus obtained by pulsed-wave Doppler) were also estimated.

Speckle-Tracking Echocardiography

All 77 patients from the current database were eligible for speckle-tracking echocardiographic analysis. Longitudinal LA strain was computed by speckle-tracking echocardiography (2D Cardiac Performance Analysis; TomTec Imaging Systems, Munich, Germany). This software, unlike previous software, performs border tracking that is better suited to a region of interest commensurate with the thin LA wall. The relative velocity is estimated, for each border point, by extracting a space-time representation along a line that passes through the tracked border and has direction orthogonal to the direction used for border tracking. The velocity vector is then obtained by the vector summation of the Lagrangian (border) and Eulerian (relative) velocity contributions. The entire process makes use of the time periodicity to ensure a periodic result and avoid the drift effect. Strain is defined as the instantaneous local border lengthening or shortening, St ( t ) = [ L ( t ) − L 0 ]/ L 0 , with respect to one arbitrary instant, t 0 , when L ( t 0 ) = L 0 , taken at the end of diastole (the electrocardiographic R wave). Strain rate is defined as the rate of lengthening/shortening as SR ( t ) = L −1 ( t )d L /d t .

Global LA strain was estimated by taking the average of longitudinal strain data obtained from the apical four-chamber and two-chamber projections. Data from a total of 12 LA segments (annular, mid, and superior segments along the septal, lateral, anterior, and inferior LA walls using apical four-chamber and two-chamber images) were averaged to determine global longitudinal strain at the end of LV ejection (LA reservoir phase; Figures 1 and 2 ). Regional LA strain was computed from the annular, mid, and superior segments from both four-chamber and two-chamber projections. The peak strain rate was measured during LV ejection (LA reservoir phase), and the early diastolic systolic strain rate was measured during LV early diastole (LA conduit phase). Assessment of LV strain was regarded as suboptimal when either (1) speckle tracking could not be obtained for at least four of the six myocardial segments in each view or (2) a theoretically unacceptable value or values were obtained.

Figure 1

Characterization of LA motion in (A) a control subject and (B) a patient with AF.

Figure 2

Longitudinal LA strain in (A) a control subject and (B) a patient with AF.

Follow-Up Data

Of the original 35 patients, 26 patients consented to participate in additional follow-up data analysis; the remaining patients either received follow-up care elsewhere or did not consent to additional follow-up data collection. Rehospitalization for cardiac events and death was recorded for each of the 26 individuals. Hospitalizations, cardiac events, and all-cause mortality were recorded from the date of echocardiography through May 2010, resulting in a median length of follow-up of 394 days. Cardiac events were defined as episodes of heart failure, AF with rapid ventricular rate, other arrhythmias, acute coronary syndromes, stroke, or a cardioembolic event that required hospitalization.

Statistical Analysis

Data are presented as mean ± SD. Unpaired t tests were performed to compare echocardiographic data between patients and controls. Comparison of the prevalence of comorbid conditions (diabetes, hypertension, and other medical illnesses) was made using the χ 2 test. P values < .05 were considered statistically significant. Linear regression analysis was performed in all patients with AF and control subjects for identifying correlates of global longitudinal LA strain. We also performed logistic regression analyses in patients with AF to determine the predictors of a CHADS 2 score ≥ 2. The associations of CHADS 2 score, indexed LA volume, and longitudinal LA strain with outcomes were assessed in a series of Cox models. The incremental value of longitudinal LA strain over indexed LA volume and CHADS 2 score was assessed in a series of Cox models in which the first model consisted of CHADS 2 score ≥ 2 entered as a test group. Each echocardiographic variable was then entered into separate models in combination with CHADS 2 score. Reliability of the LA speckle-tracking parameters was assessed by interobserver and intraobserver variability. Ten patients from each group were studied in duplicate by two observers (P.L.A. and G.C.) for LA emptying fraction, global longitudinal LA strain, and LA peak systolic and end-systolic strain. Bland-Altman plots and linear regression methods were used to assess the reproducibility.


Baseline characteristics are presented in Table 1 . Patients with AF were older than the control subjects ( P = .005) and had a significantly higher prevalence of hypertension ( P = .02) and heart failure ( P < .001).

Table 1

Baseline characteristics of the study subjects

Demographic and clinical characteristic Patients with AF ( n = 36) Control subjects ( n = 41)
Age (y) (mean ± SD) 74 ± 10 66 ± 16
Men 21 18
Comorbid conditions
Hypertension 12 5
Coronary artery disease 8 9
Heart failure 12 1
Diabetes 5 2
Stroke 3 3
Others 6 4

P = .005.

P = .02.

P < .001 by χ 2 test.

All echocardiographic parameters except LV diameter and LV filling pressure differed between patients with AF and controls ( Table 2 ). Indexed LA volume was significantly higher in patients with AF than in controls ( P < .001).

Table 2

Conventional echocardiographic data

Variable Patients with AF ( n = 36) Control subjects ( n = 41) P
LVIDd (mm) 47 ± 6 46 ± 7 .70
Mean AV plane motion (mm) 10 ± 2 13 ± 2 <.001
LVEF (%) 47 ± 10 58 ± 7 <.001
TAPSE (mm) 18 ± 4 22 ± 4 <.001
E/E′ ratio 9 ± 3 9 ± 4 .90
Maximal LA volume (mL) 92 ± 41 62 ± 26 <.001
Minimal LA volume (mL) 56 ± 32 21 ± 15 <.001
LA emptying fraction (%) 42 ± 16 67 ± 13 <.001
LAVI (mL/m 2 ) 43 ± 13 31 ± 8 <.001

Data are expressed as mean ± SD.

AV , Atrioventricular; LAVI , LA volume indexed to body mass area; LVEF , LV ejection fraction; LVIDd , LV internal diameter during diastole; TAPSE , tricuspid annular plane systolic excursion by M-mode echocardiography.

Mean AV plane motion is the average of four AV plane excursions during systole by M-mode echocardiography.

The LA emptying fraction was reduced in patients with AF compared with controls (42 ± 16% vs 67 ± 13%, P < .001). Of the total of 924 LA segments analyzed in 36 patients with AF and 41 controls, analysis of regional strain was feasible in 898 segments (97%). Regional strain data are provided in Figure 3 , in which dispersion of data is more pronounced in the controls than in the patients with AF. The standard deviation of regional strain correlated with the LA emptying fraction ( r = .80, P < .001; Figure 3 ). Global longitudinal LA strain was reduced in patients with AF compared with controls (17.7 ± 9.5% vs 35.5 ± 14.0%, P < .001). On pooled analysis of data from all patients with AF and controls, indexed LA volume, LV ejection fraction, atrioventricular plane displacement, and pulmonary artery systolic pressure were related to global LA longitudinal strain ( P < .05 for each), but on multivariate regression analysis ( Table 3 ), indexed LA volume and atrioventricular plane displacement were independent predictors of global LA longitudinal strain ( R = .63, P = .004 and P < .001 for indexed LA volume and atrioventricular plane displacement, respectively).

Figure 3

Regional heterogeneity of LA mechanics. (A) Each bar represents mean longitudinal strain; the error bars represent the standard deviations. (B) Total LA emptying fraction in relation to the standard deviation of LA strain.

Table 3

Univariate and multivariate regression analysis for global longitudinal LA strain in all patients with AF and control subjects

Variable Univariate regression Multivariate regression
Correlation P Coefficient SE P R 2
Indexed LA volume −0.54 .001 −0.27 0.08 .004 0.63
LVEF 0.48 .003
Mean AV plane displacement 0.65 <.001 17.86 6.17 <.001
PASP −0.39 .03

AV , Atrioventricular; LVEF , LV ejection fraction; PASP , pulmonary artery systolic pressure.

Peak systolic strain rate and early diastolic strain rate were reduced in patients with AF compared with controls: 1.46 ± 0.73 vs 0.74 ± 0.32 s −1 for systolic strain rate ( P < .001) and 1.77 ± 0.9 vs 1.01 ± 0.5 s −1 for early diastolic strain rate ( P < .001).

Logistic regression analysis in patients with AF identified global LA strain as the only echocardiographic variable that was associated with greater odds of having a CHADS 2 score ≥ 2 (odds ratio, 0.86; 95% confidence interval, 0.76–0.97; P = .02; Table 4 ). On categorizing patients into three risk groups, mild (CHADS 2 score < 2), moderate (CHADS 2 score 2 or 3), and high (CHADS 2 score > 3), LA strain showed significant attenuation ( P = .03) with increasing CHADS 2 score ( Figure 4 ). Similar trends were seen for indexed LA volume, although they were not statistically significant ( P = .17; Figure 5 ).

Table 4

Univariate predictors of CHADS 2 score ≥ 2

Variable Coefficient SE OR 95% CI P
LVEF −0.098 0.055 0.90 0.81–1.00 .07
E/E′ ratio 0.209 0.132 1.23 0.95–1.59 .11
PASP 0.086 0.049 1.08 0.98–1.20 .08
Indexed LA volume 0.062 0.036 1.06 0.99–1.14 .09
Global LA strain −0.145 0.062 0.86 0.76–0.97 .02

CI , Confidence interval; LVEF , LV ejection fraction; OR , odds ratio; PASP , pulmonary artery systolic pressure.

Figure 4

Distribution of global longitudinal strain for mild (CHADS 2 score < 2), moderate (CHADS 2 score 2 or 3), and high (CHADS 2 score > 3) risk. The central box represents the values from the lower to upper quartile (25th to 75th percentile). The middle line represents the median. The whiskers extend from the minimum to the maximum value.

Figure 5

Distribution of indexed LA volume for mild (CHADS 2 score < 2), moderate (CHADS 2 score 2 or 3), and high (CHADS 2 score > 3) risk. The central box represents the values from the lower to upper quartile (25th to 75th percentile). The middle line represents the median. The whiskers extend from the minimum to the maximum value, excluding an outlying value, which is displayed as a separate point.

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Jun 15, 2018 | Posted by in CARDIOLOGY | Comments Off on Global Left Atrial Strain Correlates with CHADS 2Risk Score in Patients with Atrial Fibrillation

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