Relationship between pulse interval and respiratory sinus arrhythmia: a time- and frequency-domain analysis of the effects of atropine

Abstract

Respiratory sinus arrhythmia (RSA) estimation is commonly used as a non-invasive index of cardiac vagal tone. To test this relationship, vagal tone was augmented or blocked using atropine. The study was carried out using 14 healthy volunteers, following beta-adrenoceptor blockade (10 mg bisoprolol per os) and during controlled respiration (0.25 Hz) in order to limit the confounding effects of cardiac sympathetic tone and respiration pattern changes. Atropine was slowly infused intravenously over a 30-min period up to a vagolytic cumulative dose of 0.04 mg/kg. The instant vagal tone was compared to the instant RSA value obtained from a time-/frequency-domain analysis of pulse interval (PI). RSA and PI varied in the same direction with an initial increase corresponding to the early vagomimetic effect of atropine followed by a decrease during the vagolytic phase. The comparative percentage fluctuations of RSA and PI over this large vagal tone range indicate that RSA is more sensitive (about twofold) than PI in reflecting fluctuations around the set point. This dissociated behaviour of PI and heart rate variability could be important to our understanding of the circulatory changes that result from fluctuations in vagal inputs to the sinus node.

Cardiovascular Autonomic Regulation in Preterm Infants: The Effect of Atropine

“…In adult rats, atropine increased HR and decreased the spectral HF peak (29,31). Similar results have been obtained in human adults, in which atropine increased HR and decreased HF spectral power (30,32,38). During sympathetic stimulation, variability of the R-R interval series showed virtually no spectral power in the HF band after atropine (30).…”

“…However, we found in all patients a marked HR increase after atropine, and thus it seems unlikely that the dose was too small. Notably, we observed no initial "paradoxal" vagomimetic period, resulting from a low dose of atropine that can be seen in adults before the vagolytic effect (32). Third, the infants are in respiratory distress.…”

“…However, parasympathetic blockade caused a great reduction in power in all frequency bands in the HR spectrum, with remaining power in the LF band (39). Studies in healthy volunteers under controlled conditions (␤-adrenoceptor blockade, metronomic breathing) show that the respiratoryassociated fluctuations are more sensitive to slight changes in vagal activity than to tonic control (32). To explain these features, it can be hypothesized that difference in the shift of HR and respiratory-associated fluctuations are controlled by independent actions of the two primary medullary source nuclei of the vagus: the nucleus ambiguus and the dorsal motor nucleus.…”

The autonomic control and functional significance of the changes in heart rate associated with air breathing in the jeju,Hoplerythrinus unitaeniatus

“…This demonstrates that respirationrelated modulation of activity at the sinoatrial node, exerted via the parasympathetic vagus, is an essential component of HRV in all animals examined to date (Medigue et al, 2001;Campbell et al, 2004;Campbell et al, 2006b). Thus, although the control of cardio-respiratory coupling events is still not completely understood in water-breathing fish, there does appear to be some commonality in the autonomic control of HRV between animals that breathe water and those that breathe air.…”

“…Pharmacological parasympathetic blockade abolishes the PSA peaks in the spectra of mammals, reptiles and waterbreathing fish (Medigue et al, 2001;Campbell et al, 2004;Campbell et al, 2006b). This demonstrates that respirationrelated modulation of activity at the sinoatrial node, exerted via the parasympathetic vagus, is an essential component of HRV in all animals examined to date (Medigue et al, 2001;Campbell et al, 2004;Campbell et al, 2006b).…”