Components of arterial systolic pressure and RR-interval oscillation spectra in a case of baroreflex failure, a human open-loop model of vascular control

Abstract

The baroreflex control of circulation is always operating and modulates blood pressure and heart rate oscillations. Thus, the study of cardiovascular variability in humans is performed in a closed-loop model and the physiology of post-sinoaortic denervation is completely unknown in humans. We dissected for the first time the different components of systolic arterial pressure (SAP) and RR-interval spectra in a patient with 'baroreflex failure' (due to mixed cranial nerve neuroma) who represents a human model to investigate the cardiovascular regulation in an open-loop condition. Interactions among cardiovascular variability signals and respiratory influences were described using the multivariate parametric ARXAR model with the following findings: (1) rhythms unrelated to respiration were detected only at frequencies lower than classical low frequency (LF; Slow-LF, around 0.02 Hz) both in SAP an RR spectra, (2) small high-frequency (HF) modulation is present and related with respiration at rest and in tilt (but for SAP only) and (3) the Slow-LF fluctuations detected both in SAP and RR oscillate independently as the multivariate model shows no relationships between SAP and RR, and these oscillations are not phase related. Thus, we showed that in a patient with impaired baroreflex arc integrity the Slow-LF rhythms for RR have a central origin that dictates fluctuations on RR at the same rhythm but unrelated to the oscillation of SAP (which may be related with both peripheral activity and central rhythms). The synchronization in LF band is a hallmark of integrity of baroreflex arc whose impairment unmasks lower frequency rhythms in SAP and RR whose fluctuations oscillate independently.

Phase synchronization of baroreflex oscillations of blood pressure and pulse interval in rats: the effects of cardiac autonomic blockade and gradual blood loss

“…Further, we examined the phase synchronization of MAP and PI using the analytic signal approach. We calculated PSI (Tass et al 1998) and compared it with squared PI-MAP coherence, an established index of baroreflex activity (Munakata et al 1994, Head et al 2001, Guasti et al 2010. According to our results, PSI informatively describes the phase coupling of MAP and PI at the frequency of Mayer waves.…”

“…Significantly lower coherence in the Mayer waves range was demonstrated in barodenervated rats compared to intact animals (Cerutti et al 1994, Head et al 2001. Desynchrony of AP and HR was also observed in the human case of baroreflex failure (Guasti et al 2010). These observations suggest that phase coupling of the oscillatory system is more sensitive to various challenges than its amplitude coupling (Pikovsky et al 2002) and poses the coherence as an informative measure of baroreflex control.…”

Low-frequency power of heart rate variability is not a measure of cardiac sympathetic tone but may be a measure of modulation of cardiac autonomic outflows by baroreflexes

“…Patients with baroreflex failure, whether from carotid endarterectomy (Timmers et al , 2004), head and neck irradiation (Timmers et al , 1999; Sharabi et al , 2003), mixed cranial nerve neuroma (Guasti et al , 2010), neurosarcoidosis (Jardine et al , 2000), or brainstem stroke (Phillips et al , 2000) have very low values for LF power. Patients who have undergone neck irradiation also have attenuated responses of LF power to drugs that increase norepinephrine release from sympathetic nerves (yohimbine, which increases exocytotic release, or tyramine, which increases non-exocytotic release, independently of cardiac sympathetic innervation (Moak et al , 2007).…”

Phase Coupling Between Baroreflex Oscillations of Blood Pressure and Heart Rate Changes in 21-Day Dry Immersion

“…Orthostatic intolerance after dry immersion is associated with a decrease in MSNA, HR, and blood pressure (Iwase et al, 2000), as in vasovagal syncope which is clearly linked to the impaired baroreflex regulation of hemodynamics (Ogoh et al, 2004;Guasti et al, 2010;Schwartz et al, 2013b). Phase synchronization of baroreflex blood pressure and MSNA oscillations disappears in patients with vasovagal syncope during head-up tilt test a few minutes before the drop in blood pressure (Schwartz et al, 2013a).…”