We investigated the change of LA function using echocardiographic parameters following ASD device closure. LA functional changes occurred during the six-month follow-up, while LA and RA geometrical changes were not significant. LA reverse remodeling was evidenced by restoration of LA late diastolic contractile function. Also, a paradoxical decrease in LA reservoir function was demonstrated.
LA deformation parameters and reverse remodeling
Strain and strain rate represent global and regional LA function, respectively, based on extent and rate of myocardial deformation [7, 9]. Strain rate can be measured using 2D speckle tracking echocardiography evaluating phasic LA function [9, 10]. LA deformation is divided into three phases of reservoir phase, conduit phase, and contraction phase. The reservoir phase encompasses from the end of ventricular diastole to mitral valve opening, and LA filling is achieved during this phase. The conduit phase occurs at early diastole, from mitral valve opening until onset of LA contraction. The contractile phase occurs at late diastole, from onset of LA contraction until mitral valve closure in sinus rhythm [7, 10]. Reservoir function can be modulated by LA relaxation and preload. Conduit function can be affected by LA afterload and LV relaxation. Contractile function can change with intrinsic LA contraction. There are several reports about LA deformation properties in AF patients. AF is one of the most common causes of LA dysfunction, and remodeling and impaired atrial functions have been associated with increased risk of AF . When reverse remodeling is achieved, strain rate recovers and showed a greater likelihood of maintaining sinus rhythm after rhythm control in AF patients [12,13,14]. There are several reports about change of LA function after ASD closure, and results were controversial. Sinem et al. reported that strain and strain rate decreased at one month after closure . Another study showed that the LA reservoir and conduit functions were abnormal after a mean follow-up of 44.5 months; however, they did not show baseline parameters before the procedure . In our study, global LA contractile function was improved after six months of follow-up, and global LA reservoir function decreased. Also, there was no change of conventional echocardiographic parameters, including atrial size and Doppler measurements. The improvement of LA contractile function represents LA reverse remodeling before geometric change. Meanwhile, LA reservoir function showed paradoxical decrease after device closure in this study. This decrease might be explained by the differences of chamber preload. In ASD patients, chronic left to right atrial shunt flow causes chronic volume overload to RA, right ventricle (RV), and LA. After closure of ASD, RA, RV, and LA volume overload decrease and result in preload decrease. Strain rate during systole and early diastole were decreased by the decrease in preload. However, late diastole is preload independent . Therefore, the paradoxical decrease in reservoir function was affected by preload decrease, and LA reverse remodeling can be confirmed with improvement of LA contractile function, which is independent of preload change.
There were several limitations in this study. First, because this study included a small number of patients, it may have insufficient power to determine the statistical significance of the atrial geometric change. Nevertheless, we demonstrated change in LA function. Second, this study was a prospective cohort study, and we could not demonstrate anatomical change at the six-month follow-up. Additional larger and longer-term follow-up studies should be considered. Third, we did not investigate RA remodeling affecting the occurrence of AF in patients with ASD. Finally, there was no patient who showed recurrence or newly developed AF after device closure. We included a relatively young population, and this could be one of the factors affecting development of AF. More study is needed about LA and RA reverse remodeling in AF recurrence patients.