Showing papers by "Chiara Cogliati published in 1998"
TL;DR: Cardiovascular variability is altered in patients with OSA, evident even in the absence of hypertension, heart failure, or other disease states and may be linked to the severity of OSA.
Abstract: Background—Altered cardiovascular variability is a prognostic indicator for cardiovascular events. Patients with obstructive sleep apnea (OSA) are at an increased risk for cardiovascular disease. We tested the hypothesis that OSA is accompanied by alterations in cardiovascular variability, even in the absence of overt cardiovascular disease. Methods and Results—Spectral analysis of variability of muscle sympathetic nerve activity, RR interval, and blood pressure were obtained during undisturbed supine rest in 15 patients with moderate-to-severe OSA, 18 patients with mild OSA, and 16 healthy control subjects in whom sleep disordered breathing was excluded by complete overnight polysomnography. Patients with OSA were newly diagnosed, never treated for OSA, and free of any other known diseases. Patients with moderate-to-severe OSA had shorter RR intervals (793±27 ms) and increased sympathetic burst frequency (49±4 bursts/min) compared with control subjects (947±42 ms; 24±3 bursts/min; P=0.008 and P<0.001, re...
563 citations
TL;DR: The reduction of complexity of the neural control obtained by spinalization decreases the regularity in the sympathetic outflow, thus pointing to a weaker coupling between the sympathetic discharge and ventilation, and the proposed index is obtained without an a-priori definition of the pattern length.
Abstract: A new method for measuring the regularity of a process over short data sequences is reported. This method is based on the definition of a new function (the corrected conditional entropy) and on the extraction of its minimum. This value is taken as an index in the information domain quantifying the regularity of the process. The corrected conditional entropy is designed to decrease in relation to the regularity of the process (like other estimates of the entropy rate), but it is able to increase when no robust statistic can be performed as a result of a limited amount of available samples. As a consequence of the minimisation procedure, the proposed index is obtained without an a-priori definition of the pattern length (i.e. of the embedding dimension of the reconstructed phase space). The method is validated on simulations and applied to beat- to-beat sequences of the sympathetic discharge obtained from decerebrate artificially ventilated cats. At control, regular, both quasiperiodic and periodic (locked to ventilation) dynamics are observed. During the sympathetic activation induced by inferior vena cava occlusion, the presence of phase-locked patterns and the increase in regularity of the sympathetic discharge evidence an augmented coupling between the sympathetic discharge and ventilation. The reduction of complexity of the neural control obtained by spinalization decreases the regularity in the sympathetic outflow, thus pointing to a weaker coupling between the sympathetic discharge and ventilation.
266 citations
TL;DR: In this article, the authors performed spectral analysis of RR, blood pressure, and respiration in 2 patients with severe congestive heart failure before and after LVAD implantation and found that the arterial baroreflex is the predominant determinant of the LF component of RR variability.
Abstract: Background—Short-term variability of RR interval and blood pressure occurs predominantly at low frequency (LF; ≈0.1 Hz) and high frequency (≈0.25 Hz). The arterial baroreflex is thought to be the predominant determinant of the LF component of RR variability. Patients with severe congestive heart failure (CHF) have an attenuated or absent LF oscillation in RR variability. The left ventricular assist device (LVAD) offers a unique possibility for analysis of spectral oscillations in RR interval independent of any effects of blood pressure that influence these oscillations via the baroreflex. Methods and Results—We performed spectral analysis of RR, blood pressure, and respiration in 2 patients with CHF before and after LVAD implantation. LF components of the RR-interval and blood pressure variability were absent in both CHF patients before LVAD implantation. After LVAD implantation, spectral analysis of the RR interval showed restoration of a clear and predominant LF oscillation in the native hearts of both ...
172 citations
TL;DR: High-dose atropine similarly induces an increase in the HF and a decrease in the LF components of MSNA variability, which indicates central parasympathetic activation is able to modulate the oscillatory characteristics of sympathetic nerve traffic to peripheral blood vessels.
Abstract: Background—Low-dose atropine causes bradycardia either by acting on the sinoatrial node or by its effects on central muscarinic receptors increasing vagal activity. Any central muscarinic effects of high-dose atropine on RR interval are masked by peripheral muscarinic blockade at the sinoatrial node, which causes tachycardia. Effects of central parasympathetic activation on sympathetic activity are not known. Methods and Results—Using power spectral analysis of RR interval, intra-arterial blood pressure, respiration, and muscle sympathetic nerve activity (MSNA), we examined the effects of both low (2 μg/kg IV) and high (15 μg/kg IV) doses of atropine. After low-dose atropine, RR increased by 9±1% (P<0.0001), the low-frequency (LF) component (in normalized units, NU) of RR variability decreased by −32±8%, and the high-frequency (HF)NU component increased (+74±19%); hence, LF/HF of RR variability fell by 52±10% (all P<0.01). Although overall MSNA did not change, LFNU of MSNA decreased (−15±5%), HFNU of MSNA...
153 citations
TL;DR: Observations indicate that the type of left ventricle haemodynamic overload may be a quantitative determinant factor in the myocardial beta-adrenoceptor downregulation and the reduction of a pathological cardiac load leads to an upregulation of these receptors.
6 citations