Atrial septal defect (ASD) accounts for 25-30% of congenital heart defects diagnosed during adulthood.1 Ostium secundum ASD is the most common type, constituting 70% of all ASDs and 6-10% of all congenital heart defects. Left atrial (LA) and right atrial (RA) diameters and volumes are increased in ASD patients due to volume overload. ASDs cause a left-to-right shunt and chronic right chamber volume overload that can result in severe pulmonary hypertension and right heart failure. Secundum ASDs are centrally located and generally bounded by the superior and inferior limbic bands, which often makes these defects amenable to device closure.2,3

In the absence of fixed pulmonary hypertension, percutaneous ASD closure is associated with improvements in right ventricular dimensions, morphology and function and exercise physiology, and reverse right ventricular (RV) remodeling.3 However, such adaptations can be incomplete or delayed in adult patients, and atrial changes post-ASD closure are poorly understood.4

New echocardiographic methods have been developed to quantify left and right ventricular function and are important for diagnostic and prognostic assessment in various cardiovascular diseases.5,6 A new echocardiographic technique, two-dimensional (2D) speckle tracking echocardiography (STE), is capable of angle-independent tracking of myocardial deformation, enabling non-invasive and quantitative assessment of global and regional myocardial function.7

Myocardial STE measures tissue deformation within the myocardium expressed as a percentage change. Myocardial tissue lengthening and shortening give positive and negative strain values, respectively. Strain rate measures the local rate of myocardial deformation per time unit. The global strain or strain rate is calculated by computing deformation along the entire myocardial line length.8,9 This new echocardiographic method is frequently used to assess left ventricular (LV) myocardial function, but has rarely been used to examine RA and RV myocardial function. Myocardial strain and strain rate can be used to investigate RA myocardial function during each phase of the cardiac cycle. Padeletti et al. showed that RA speckle tracking analysis is significantly correlated with systolic pulmonary artery pressure and pulmonary arterial hypertension secondary to LV systolic dysfunction. They also found that assessment of RA longitudinal strain can identify pulmonary artery hypertension in congestive heart failure patients.10

The objective of the present study was to evaluate RA function by quantifying longitudinal RA strain in patients with chronic RV volume overload due to an ostium secundum ASD before and after percutaneous closure.

Baseline demographic characteristics and procedure-related clinical parameters of the study population are summarized in Table 1. The mean native secundum ASD diameter on color Doppler echocardiographic assessment was 14±5 mm (10-22 mm) and the mean diameter of the closure devices used was 18.5±7.5 mm (14-28 mm). Percutaneous closure was performed successfully in all 32 patients. There was no residual ASD in any of the patients on echocardiographic assessment at one month after the procedure. The echocardiographic measurements are given in Table 2. RV end-diastolic diameters were significantly increased but decreased significantly after ASD closure (43±5 vs. 38±4 mm, p<0.05). LA diameters (40±8 vs. 37±6 mm, p<0.05) decreased significantly after the intervention, whereas LV end-diastolic diameters (45±5 vs. 46±4 mm, NS) remained unchanged. Tricuspid annular plane systolic excursion (TAPSE) increased significantly (17.6±5.4 vs. 22.3±8.1 mm, p<0.05). After closure of the defect, a significant increase was observed in longitudinal RA strain (Table 2). Intra-observer variability for RA longitudinal strain was 3.2+1.6%.

Correlation analysis was performed between post-ASD and pre-ASD parameters. The delta value was calculated as post-ASD parameter minus pre-ASD parameter. The analysis showed negative correlations between delta RA longitudinal strain and delta RV diameter, delta RA diameter and delta pulmonary artery systolic pressure (PASP). Also, a positive correlation was found between delta RA longitudinal strain and delta TAPSE. However, there was no correlation between delta RA longitudinal strain and delta LVEF, delta LV diameter or delta LA diameter (Table 3).

The right atrium has multiple important roles during the cardiac cycle: it functions as a reservoir for systemic venous return when the tricuspid valve is closed, provides a passive conduit for blood flow during early diastole when the tricuspid valve opens, and actively expels blood during late diastole with atrial contraction.7 The right atrium has an unusual geometry and thin walls. Assessment of atrial dimensions and volume using 2D echocardiographic parameters has limitations. Measurement of atrial dimensions with M-mode and 2D echocardiography assumes the atria have an elliptical geometry,15 but this is clearly not completely true, and the variable and non-uniform geometry of the atria leads to significant differences in the measurement of atrial volumes using the biplane area-length method and biplane modified Simpson's rule.15 Anatomical and functional assessment of the RA is therefore difficult.16–18 In previous studies, 2D transthoracic echocardiographic measurements in patients with ASD demonstrated enlarged right atrium, right ventricle, and pulmonary arteries. These usually correlate with the magnitude of the left-to-right shunt.19 In the past decade, the novel echocardiographic technique of strain imaging has been used to make more accurate assessments of myocardial function.20 STE has been used in a wide range of cardiovascular conditions, including hypertension, heart failure and myocardial infarction.21,22 Conventional ways of determining systolic function rely on visual assessment of wall motion and changes in volume. However, STE measures actual tissue deformation within the myocardium.11

One of the new applications of STE is in assessment of RA myocardial function. The RA reservoir phase is a dynamic phase of the cardiac cycle. RA deformation is dependent on preload and afterload, which affect the right ventricle and consequently influence the right atrium. We therefore assessed RA myocardial function in patients with percutaneous ASD closure by focusing on the reservoir phase.

Two-dimensional STE assessment of RA myocardial function is feasible throughout the cardiac cycle. Peak RA longitudinal strain determines the reservoir phase.7 Padeletti et al. reported that RA STE significantly correlated with pulmonary pressure. They also found that RA assessment with STE can predict pulmonary artery hypertension in heart failure patients.10 We demonstrated that peak RA longitudinal strain increased significantly after percutaneous closure of secundum ASD. Our study is the first to assess the effect of percutaneous ASD closure on RA function with STE. Sakata et al. reported that RA longitudinal strain was useful for noninvasive assessment of RA dysfunction in patients with pulmonary artery hypertension. They also found that peak global RA longitudinal strain was correlated with cardiac index. Peak global RA longitudinal strain can be thus useful for the assessment of RA overload and dysfunction in pulmonary artery hypertension. This study showed an inverse correlation between PASP and peak global RA longitudinal strain.7

In our study, there was improvement in multiple echocardiographic parameters, including RV end-diastolic diameter, RA diameter, RV/LV end-diastolic diameter ratio, LA diameter and PASP at one month post-procedure. LV end-diastolic diameter and LV end-systolic diameter remained unchanged in the first month post-procedure, while LVEF and TAPSE were significantly increased. In this study, there was a positive correlation between delta RA longitudinal strain and delta LVEF and TAPSE and a negative correlation between delta RA longitudinal strain and delta RV myocardial performance index, RV diameter, RA diameter and PASP. Our finding of decreased RA and LA dimensions after percutaneous ASD closure is in agreement with similar reports in previous studies. For example, Akula et al. found a significant decrease in RV volumes in the first month after ASD closure that continued up to six months,23 and Veldtman et al. found that right heart morphology undergoes rapid improvement within one month of percutaneous ASD closure.24 Atashband et al. showed that percutaneous ASD closure in adults is effective, leading to reverse remodeling and better functional capacity,25 while Thilén et al. found that cardiac remodeling after ASD closure in the adult is common and is generally completed within the first half year after closure.26

STE can be used for myocardial assessment in all dimensions (longitudinal, radial, and circumferential). In our study, we measured RA longitudinal strain only. Only one cardiac cycle was studied, and so respiratory variations may be a source of sample error. The software used for STE analysis was originally designed for the left ventricle, but in the present study it was applied to the right atrium. Defects in the atrial septum and the presence of an occlusion device may have affected RA longitudinal strain values.

Volume overload is associated with decreased strain values, which return to normal when the volume overload is abolished. In this study, RA longitudinal strain measured by 2D-STE was useful to assess the effect of percutaneous ASD closure on RA dysfunction in the reservoir phase. STE can be considered a feasible and reproducible noninvasive technique for the assessment of RA longitudinal deformation dynamics in patients with ASD.

The authors have no conflicts of interest to declare.