Clinical Investigation
Left Atrial Function
Two-Dimensional Speckle-Tracking Echocardiography of the Left Atrium: Feasibility and Regional Contraction and Relaxation Differences in Normal Subjects

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Background

Increased left atrial (LA) size and reduced global contractility are related to adverse cardiac events. The potential incremental value of assessing regional LA contractility is unknown. To assess the feasibility of measuring this variable angle, independent 2-dimensional speckle-tracking strain echocardiography (2D-SpTr) was used to measure regional LA strain (ɛ) and strain rate (SR) in normal individuals of various ages.

Methods

From standard apical views, 2D-SpTr was used on 84 normal subjects to measure longitudinal velocity, ɛ, and SR in 13 LA segmental regions. The values obtained from the different atrial regions were compared with each other and corresponding LA volumes before and after LA contraction.

Results

Regional LA ɛ and SR could be measured in 77 of 84 normal subjects (94%). A consistent pattern of differences in LA regional function was noted with the annular regions, and particularly the inferior wall having a larger average peak velocity and ɛ and SR values in comparison with the mid and superior LA segments. Peak ɛ and SR during LA contraction had only a modest correlation with LA volumes.

Conclusion

The angle-independent technique of 2D-SpTr tracking can analyze regional LA ɛ and SR in 94% of normal subjects. Regional differences in LA contractility are consistently present. The annular regions, and especially the inferior wall have the highest values for LA ɛ and SR. The significance of these findings and their possible use in identifying disease states will require further study.

Section snippets

Subjects

Eighty-two healthy volunteers (50 female, 32 male) aged 18 to 80 years old (mean 45 ± 11 years) with good 2D echo image quality underwent a complete echo-Doppler and 2D-SpTr examination. Inclusion criteria for normal subjects included 1) no clinical history of CV disease or diabetes; 2) normal blood pressure (≤125/80 mm Hg); 3) a body mass index (BMI) ≤ 30 kg/m2; 4) normal sinus rhythm between 50 and 85 beats/min without conduction abnormalities; 5) normal left ventricular (LV) wall thickness,

Statistical Analysis

All variables were expressed as mean ± standard deviation. The velocity, ɛ, and SR variables for LA function were compared among the 13 regions, during atrial contraction, relaxation, and LA peak filling, with a 1-way analysis of variance. When differences were found between means, a Bonferroni t test was performed to determine which regions were different. Linear regression analysis was performed to determine the relationship of LA regional peak velocity, ɛ, and SR, and the 3 LA measured

Study Group Clinical Characteristics

We screened 100 consecutive volunteers who were believed to be healthy and have a normal heart. Eighteen volunteers were eliminated because of an elevated blood pressure or an abnormal electrocardiogram. Of the 82 volunteers in the final study population, 48 were female (60%) and 29 were male (40%). The mean age was 45 ± 11 years. The average BMI was 25.7 ± 4.1. Mean systolic blood pressure was 112 ± 11 mm Hg, and diastolic blood pressure was 70 ± 8 mm Hg.

Two-dimensional Speckle Tracking of the Left Atrium: Feasibility, Waveforms, and Reproducibility

For data from any of the 3 apical views

Discussion

We have shown that 2D-SpTr, an angle-independent technique for measuring myocardial deformation, is able to analyze global and regional LA longitudinal contractility and relaxation in 94% of normal individuals with good reproducibility. Furthermore, as imaged by the 2D apical transducer position, a consistent velocity gradient was found during LA contraction, with the highest values in the annular regions and lower values in the mid-wall and roof. Among individual LA regions, the inferior wall

Limitations

2D-SpTr of the left atrium is more difficult and time-consuming than assessing segmental LV function. Although we demonstrated a 94% feasibility rate in obtaining data from non-obese (BMI of < 30) normal subjects, it would be expected that this success rate will be lower in heavier patients or those with pulmonary diseases. The left atrium is farther from the transducer in the apical views, and the LA myocardium is thinner and “brighter” than the LV myocardium with fewer speckle kernels to

Conclusions

LA regional contraction and relaxation variables can be assessed using 2D-SpTr in 94% of normal individuals of various ages. Differences in time to peak SR with LA contraction in the different LA regions follow the reported electrical activation sequence. Regional differences in peak velocity, ɛ, and SR during LA contraction were demonstrated, suggesting that LA myocardial architecture is specialized to optimize LV end-diastolic filling, LA early systolic filling, and cardiac fluid dynamics.

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This work was supported by the A.J. Sigismunda Palumbo Charitable Trust.

Dr Vianna-Pinton is supported by the “Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq),” Brazil. There are no financial conflicts on the part of any authors.

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