The role of sympathetic and vagal cardiac control on complexity of heart rate dynamics

Author(s)

Virgilio Silva, Luiz Eduardo ; Aguiar Silva, Carlos Alberto ; Salgado, Helio Cesar ; Fazan, Jr., Rubens

• Document type: Journal article
• Source: AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY; v. 312, n. 3, p. H469-H477, MAR 2017.
• Web of Science Citations: 17

Abstract

Analysis of heart rate variability (HRV) by nonlinear approaches has been gaining interest due to their ability to extract additional information from heart rate (HR) dynamics that are not detectable by traditional approaches. Nevertheless, the physiological interpretation of nonlinear approaches remains unclear. Therefore, we propose long-term (60 min) protocols involving selective blockade of cardiac autonomic receptors to investigate the contribution of sympathetic and parasympathetic function upon nonlinear dynamics of HRV. Conscious male Wistar rats had their electrocardiogram (ECG) recorded under three distinct conditions: basal, selective (atenolol or atropine), or combined (atenolol plus atropine) pharmacological blockade of autonomic muscarinic or beta(1)-adrenergic receptors. Time series of RR interval were assessed by multiscale entropy (MSE) and detrended fluctuation analysis (DFA). Entropy over short (1 to 5, MSE1-5) and long (6 to 30, MSE6-30) time scales was computed, as well as DFA scaling exponents at short (alpha(short), 5 <= n <= 15), mid (alpha(mid), 30 <= n <= 200), and long (alpha(long), 200 <= n <= 1,700) window sizes. The results show that MSE1-5 is reduced under atropine blockade and MSE6 -30 is reduced under atropine, atenolol, or combined blockade. In addition, while atropine expressed its maximal effect at scale six, the effect of atenolol on MSE increased with scale. For DFA, alpha(short) decreased during atenolol blockade, while the alpha(mid) increased under atropine blockade. Double blockade decreased alpha(short) and increased alpha(long). Results with surrogate data show that the dynamics during combined blockade is not random. In summary, sympathetic and vagal control differently affect entropy (MSE) and fractal properties (DFA) of HRV. These findings are important to guide future studies. NEW \& NOTEWORTHY Although multiscale entropy (MSE) and detrended fluctuation analysis (DFA) are recognizably useful prognostic/diagnostic methods, their physiological interpretation remains unclear. The present study clarifies the effect of the cardiac autonomic control on MSE and DFA, assessed during long periods (1 h). These findings are important to help the interpretation of future studies. (AU)

• FAPESP's process: 13/20549-7 - New insights in cardiovascular regulation under physiological and pathophysiological condition
• Grantee: Helio Cesar Salgado
• Support Opportunities: Research Projects - Thematic Grants