Is atrial septal defect alone able to affect the cardiac autonomic function or are there different factors that influence this function?

We read with a great interest the paper by Özyılmaz et al. (1) entitled “Heart rate variability improvement in children using transcatheter atrial septal defect closure” published in the Anatol J Cardiol 2015 Mar 4. The authors aimed to evaluate cardiac autonomic functions in children who underwent transcatheter closure of atrial septal defect (ASD) using analysis of heart rate variability (HRV) parameters. They concluded recovery of HRV indices approximately 6 months after transcatheter ASD closure. ASD is a frequently seen congenital heart disease characterized with left-to-right shunting and dilation of the right cardiac chambers and pulmonary artery, which might result in heart failure, arrhythmia, and thromboembolic events as well as increased mortality. The enlarged right ventricle usually returns to normal size during the first 24 months after transcatheter device closure or surgical repair, although this normalization may persist for up to 5 years after defect closure (2). As mentioned in the article by Özyılmaz et al. (1), HRV impairment in patients with ASD has been attributed to right ventricular filling and right atrial tension due to left-to-right blood flow through ASD (3). However, in the study by Özyılmaz et al. (1), no data demonstrating dimensions of cardiac chambers before and after the transcatheter closure are available, and we do not know whether the initial dimensions are significantly different from those measured 6 months after transcatheter closure. In addition, the mean diameter of ASD as well as the range of the diameter of the defect in the study population is not mentioned in the article. With these additional data, we believe that readers of the journal can more easily understand whether the size of the defect and the dimensions of cardiac chambers have an effect on HRV parameters. The interpretation of HRV analysis is not as simple as thought because of various factors that influence HRV indices, which might be affected by many variables such as hyperlipidemia and blood pressure (3-5). We think that it would be more helpful to demonstrate blood pressure levels and blood lipid profiles of the study population in terms of showing no variable affecting HRV parameters rather than ASD. Thus, one can understand whether ASD alone really impairs the cardiac autonomic function, which has a prognostic importance for survival (5).