Breakdown of the Intermediate-Term Fractal Scaling Exponent in Sinus Node Dysfunction - New Method for Non-Invasive Evaluation of Sinus Node Function -

Abstract

Circulation Journal Official Journal of the Japanese Circulation Society http://www. j-circ.or.jp inus node dysfunction (SND), also referred to as "sick sinus syndrome", is a common cause of cardiac syncope. 1 Sinus bradycardia (SB) is not only an incidental finding in otherwise healthy individuals, particularly in young adults, but also an electrocardiographic manifestation of SND. 2-5 Differentiation of so-called pathologic SB (due to intrinsic SND), from normal SB, is important in the diagnosis and management of SND.Heart rate variability (HRV) analysis, through classical linear methods, either in the time or the frequency domain, provides quantitative and non-invasive measures of the activity of the autonomic nervous system. 6,7 Information carried by the heart rate signal, however, may not be totally explained by this linear approach. 8-13 Non-linear dynamical system analysis based on the theories of fractal scaling and complexity have gained interest, because they may reveal information hidden in the regulatory system that cannot be detected using conventional methods. 14-20 Pathological states and aging are associated with distinctive alterations in these scaling properties, which could be of practical diagnostic and prognostic use. To date, the short-term scaling exponent (DFAα1) of detrended fluctuation analysis (DFA) has demonstrated greater clinical discrimination of various cardiac diseases.Most previous studies regarding heart rate dynamics and its interpretations were carried out in the presence of intact sinus node activity. We assumed that, if a dysfunctional sinus node does not respond appropriately to neuroautonomic input, then alteration or breakdown of the fractal scaling and complexity of heart rate dynamics would ensue. Little information exists concerning the non-linear behavior of sinus node pacemaker activity in SND. The purpose of the present study was to characterize the heart rate dynamics of SB in SND and to test Background: The aim of the present study was to characterize the heart rate dynamics of sinus bradycardia (SB) from sinus node dysfunction (SND) using non-linear dynamical system analysis. No data are yet available on how the dynamics change in the presence of SND.

Fractal complexity alternations in paroxysmal atrial fibrillation patients with and without recurrence after pulmonary vein isolation

“…Furthermore, Shin et al discovered that patients with sinus node dysfunction significantly reduced their DFA slope2 levels, indicating that diseased sinus node may break down long‐term fractal complexity (Shin et al, 2011 ). In our study, compared to pre‐PVI level, the DFA slope2 increased significantly 1–3 months and 6–12 months post‐PVI, in the non‐recurrence group, whereas there was only a significant increase between pre‐PVI and 1–3 months post‐PVI in the recurrence group.…”

Effects of Cardiac Resynchronization Therapy on Cardio-Respiratory Coupling

“…However, we expected statistically significant changes in the value of this exponent both in responders and non-responders, especially since this is the only parameter that separated these two groups of patients at the baseline examination. Our results indicate that α 2 RR should not be considered only as an indicator of the state of ANS, i.e., the degree of blockade of the ß receptors but also as a marker of preservation of the function of the sinoatrial node cells [ 51 ]. In our study, in CRT non-responders, α 2 (RR) practically does not change, so the values of this parameter between responders and non-responders at the follow-up do not differ significantly due to the decrease in α 2 (RR) in CRT responders.…”

Differentiation of Heart Failure Patients by the Ratio of the Scaling Exponents of Cardiac Interbeat Intervals

“…In the literature, it can be found that the increase in α 1 is usually related to vagal withdrawal (Tulppo et al, 2001; Castiglioni et al, 2011) but in this HF states probably with preserved feedback loops of regulatory mechanisms. Tendency to decreased α 2 in the fourth cluster may be related to sinus node dysfunction (Shin et al, 2011) or the β-receptor blockade (Castiglioni et al, 2011). It is believed that complexity of interbeat interval fluctuations is generated solely by ANS activity and that quantified linear and non-linear parameters of HRV are quantifiers of modulatory mechanisms of ANS.…”

“…Hotta et al (2005) showed that α 2 is a more powerful measure for predicting cardiac morbidity and mortality. In the study of Shin et al (2011) long-term scaling exponent was the only parameter which was capable of discriminating differences in heart rate dynamics between patients with sinus node dysfunction. They concluded that reduced value of α 2 is a robust measure and could be an adjunctive tool for improvement of diagnostic performance in detection of sinus node dysfunction.…”