Abstract
Spectral analysis of heart rate (HR) has been widely used to assess the autonomic cardiovascular control. A nonlinear approach, known as symbolic analysis, has been reported to be very useful to assess the autonomic control of cardiovascular system in humans, but very few studies reported on the differences between these two approaches on experimental models. Two distinct approaches were used to elicit autonomic changes in conscious Wistar rats: (1) pharmacological blockade of cardiac autonomic receptors with atenolol (ATE, N = 9) or methylatropine (ATR, N = 9) and (2) mild changes in arterial pressure (AP) induced by phenylephrine (PHE, N = 9) or sodium nitroprusside (NPS, N = 9). Series of cardiac interval (CI) and systolic AP (SAP) were assessed using spectral analysis and symbolic dynamics. Results show that, for spectral analysis, the power in high frequency band of CI and the power in low frequency band of SAP are the most reliable indices of vagal and sympathetic modulation, respectively. For symbolic analysis, results point 0V% and 1V% to be related to sympathetic and 2UV% to vagal modulation. Interestingly, the incidence of 1V patterns, hitherto with unknown meaning, was revealed the best index of sympathetic modulation in the rat and should be accounted for in the future studies.
Highlights
The knowledge of the link between oscillatory components of heart rate (HR) and autonomic modulation of the heart, as demonstrated by Akselrod in early eighties[1], has opened a fruitful field of investigation
Vagal activation induced by the rise in arterial pressure (AP) (PHE) led to a marked increase in the power of cardiac interval (CI) spectra at both low frequency (LF) and HF bands
Two distinct protocols were applied to elicit sympathovagal changes: (1) pharmacological blockade of cardiac autonomic receptors and (2) mild changes in AP causing baroreflex-mediated changes in autonomic drive
Summary
The knowledge of the link between oscillatory components of heart rate (HR) and autonomic modulation of the heart, as demonstrated by Akselrod in early eighties[1], has opened a fruitful field of investigation. Most data indicate that oscillations of HR in LF represent a combination of both sympathetic and parasympathetic modulation of the autonomic control to the heart[4]. One of the main drawbacks of spectral analysis is that it is a linear method In other words, it considers HR variability (HRV) time series as composed by a linear combination of the independent oscillatory components, where interactions between those components are neglected. Several studies showed that some indexes provided by symbolic dynamics are highly correlated with the sympathetic and parasympathetic modulation to the heart and vessels[6]. In the present study we compared spectral and symbolic analysis as tools to assess the autonomic cardiac modulation in conscious rats. Spectral and symbolic analyzes were calculated from the same animals and the efficacy of both approaches to provide valid information about autonomic cardiac modulation were evaluated
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