Transfer Function Gain Between Heart Period and QT Variabilities Increases During Sympathetic Activation Induced by Head-up Tilt

2021 ◽  
Author(s):  
Vlasta Bari ◽  
Beatrice De Maria ◽  
Francesca Gelpi ◽  
Beatrice Cairo ◽  
Anielle CM Takahashi ◽  
...  
Keyword(s):  
Transfer Function ◽  
Sympathetic Activation ◽  
Heart Period ◽  
Head Up Tilt ◽  
Transfer Function Gain

scholarly journals Arterial-cardiac baroreflex function: insights from repeated squat-stand maneuvers

2009 ◽  
Vol 297 (1) ◽  
pp. R116-R123 ◽  
Author(s):  
Rong Zhang ◽  
Jurgen A. H. R. Claassen ◽  
Shigeki Shibata ◽  
Sinem Kilic ◽  
Kristin Martin-Cook ◽  
...  
Keyword(s):  
Transfer Function ◽  
Arterial Pressure ◽  
Body Position ◽  
The Elderly ◽  
Elderly Subjects ◽  
Pulley System ◽  
New Approach ◽  
Baroreflex Function ◽  
Effects Of Aging ◽  
Transfer Function Gain

To assess baroreflex function under closed-loop conditions, a new approach was used to generate large and physiological perturbations in arterial pressure. Blood pressure (BP) and R-R interval were recorded continuously in 20 healthy young (33 ± 8 yr) and eight elderly subjects (66 ± 6 yr). Repeated squat-stand maneuvers at the frequencies of 0.05 and 0.1 Hz were performed to produce periodic oscillations in BP to provoke the baroreflex. To assess the effects of the muscle reflex and/or central command on the baroreflex, passive squat-stand maneuvers were conducted using a pulley system to assist changes in body position. Transfer function between changes in BP and R-R interval was estimated to assess the arterial-cardiac baroreflex. Relative to resting conditions, large and coherent oscillations in BP and R-R interval were produced during both active and passive squat-stand maneuvers. However, changes in BP were smaller during passive than during active maneuvers. Changes in R-R interval were reduced commensurately. Therefore, transfer function gain did not change between the two maneuvers. Compared with the young, transfer function gain was reduced and the phase became more negative in the elderly, demonstrating the well-known effects of aging on reducing baroreflex sensitivity. Collectively, these findings suggest that the changes in R-R interval elicited by BP perturbations during squat-stand maneuvers are mediated primarily by a baroreflex mechanism. Furthermore, baroreflex function can be assessed using the transfer function method during large perturbations in arterial pressure.

Influences of neural mechanisms on heart period and arterial pressure variabilities in quadriplegic patients

1994 ◽  
Vol 266 (3) ◽  
pp. H1112-H1120 ◽  
Author(s):  
S. Guzzetti ◽  
C. Cogliati ◽  
C. Broggi ◽  
C. Carozzi ◽  
D. Caldiroli ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Spectral Component ◽  
Systolic Arterial Pressure ◽  
Neural Mechanisms ◽  
Heart Period ◽  
Recording Session ◽  
Sympathetic Modulation ◽  
Arterial Pressure Variability ◽  
Head Up Tilt ◽  
Vasomotor Activity

The heart period (R-R) variability power spectrum presents two components, at low (LF; approximately 0.10 Hz) and high (approximately 0.25 Hz) frequencies, whose reciprocal powers appear to furnish an index of sympathovagal interaction modulating heart rate. In addition, the LF component of the systolic arterial pressure variability spectrum furnishes a marker of sympathetic modulation of vasomotor activity. The contribution of spinal and supraspinal neural circuits to the genesis of these rhythmic oscillatory components remains largely unsettled. Therefore we performed spectral analysis of R-R and systolic arterial pressure variabilities in 15 chronic neurologically complete quadriplegic patients (QP) and in 15 control subjects during resting conditions, controlled respiration, and head-up tilt. At rest, in seven QP the LF component was undetectable in both cardiovascular variability spectra; in two QP this component was present only in R-R variability spectrum, whereas the remaining six showed a significantly reduced LF in both signals. In QP, the LF component, when present, underwent paradoxical changes with respect to controls, decreasing during tilt and increasing during controlled respiration. In five QP in whom the recording session was repeated after 6 mo, a significant increase in LF was observed in both variability spectra. These data confirm the finding that a disconnection of sympathetic outflow from supraspinal centers can cause the disappearance of the LF spectral component. However, LF presence in some QP supports the hypothesis of a spinal rhythmicity likely to be modulated by the afferent sympathetic activity.

scholarly journals Impact of mild orthostatic stress on aortic-cerebral hemodynamic transmission: insight from the frequency domain

2017 ◽  
Vol 312 (5) ◽  
pp. H1076-H1084 ◽  
Author(s):  
Jun Sugawara ◽  
Tsubasa Tomoto ◽  
Tomoko Imai ◽  
Seiji Maeda ◽  
Shigehiko Ogoh
Keyword(s):  
Transfer Function ◽  
Frequency Domain ◽  
Systemic Vascular Resistance ◽  
Vascular Resistance ◽  
Low Frequency ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Slow Oscillations ◽  
Transfer Function Gain ◽  
The Brain

High cerebral pressure and flow fluctuations could be a risk for future cerebrovascular disease. This study aims to determine whether acute systemic vasoconstriction affects the dynamic pulsatile hemodynamic transmission from the aorta to the brain. We applied a stepwise lower body negative pressure (LBNP) (−10, −20, and −30 mmHg) in 15 young men to induce systemic vasoconstriction. To elucidate the dynamic relationship between the changes in aortic pressure (AoP; estimated from the radial arterial pressure waveforms) and the cerebral blood flow velocity (CBFV) at the middle cerebral artery (via a transcranial Doppler), frequency-domain analysis characterized the beat-to-beat slow oscillation (0.02–0.30 Hz) and the intra-beat rapid change (0.78–9.69 Hz). The systemic vascular resistance gradually and significantly increased throughout the LBNP protocol. In the low-frequency range (LF: 0.07–0.20 Hz) of a slow oscillation, the normalized transfer function gain of the steady-state component (between mean AoP and mean CBFV) remained unchanged, whereas that of the pulsatile component (between pulsatile AoP and pulsatile CBFV) was significantly augmented during −20 and −30 mmHg of LBNP (+28.8% and +32.4% vs. baseline). Furthermore, the relative change in the normalized transfer function gain of the pulsatile component at the LF range correlated with the corresponding change in systemic vascular resistance ( r = 0.41, P = 0.005). Regarding the intra-beat analysis, the normalized transfer function gain from AoP to CBFV was not significantly affected by the LBNP stimulation ( P = 0.77). Our findings suggest that systemic vasoconstriction deteriorates the dampening effect on the pulsatile hemodynamics toward the brain, particularly in slow oscillations (e.g., 0.07–0.20 Hz). NEW & NOTEWORTHY We characterized the pulsatile hemodynamic transmission from the heart to the brain by frequency-domain analysis. The low-frequency transmission was augmented with a mild LBNP stimulation partly due to the elevated systemic vascular resistance. A systemic vasoconstriction deteriorates the dampening effect on slow oscillations of pulsatile hemodynamics toward the brain.

Temporal asymmetries of short-term heart period variability are linked to autonomic regulation

2008 ◽  
Vol 295 (2) ◽  
pp. R550-R557 ◽  
Author(s):  
A. Porta ◽  
K. R. Casali ◽  
A. G. Casali ◽  
T. Gnecchi-Ruscone ◽  
E. Tobaldini ◽  
...  
Keyword(s):  
Autonomic Regulation ◽  
Heart Period ◽  
Short Term ◽  
Time Reversibility ◽  
Heart Period Variability ◽  
Period Variability ◽  
Healthy Humans ◽  
Inclination Angles ◽  
Head Up Tilt ◽  
Important Shift

We exploit time reversibility analysis, checking the invariance of statistical features of a series after time reversal, to detect temporal asymmetries of short-term heart period variability series. Reversibility indexes were extracted from 22 healthy fetuses between 16th to 40th wk of gestation and from 17 healthy humans (aged 21 to 54, median = 28) during graded head-up tilt with table inclination angles randomly selected inside the set {15, 30, 45, 60, 75, 90}. Irreversibility analysis showed that nonlinear dynamics observed in short-term heart period variability are mostly due to asymmetric patterns characterized by bradycardic runs shorter than tachycardic ones. These temporal asymmetries were 1) more likely over short temporal scales than over longer, dominant ones; 2) more frequent during the late period of pregnancy (from 25th to 40th week of gestation); 3) significantly present in healthy humans at rest in supine position; 4) more numerous during 75 and 90° head-up tilt. Results suggest that asymmetric patterns observable in short-term heart period variability might be the result of a fully developed autonomic regulation and that an important shift of the sympathovagal balance toward sympathetic predominance (and vagal withdrawal) can increase their presence.

Sympathetic-Parasympathetic Activation During Spontaneous Attacks of Cluster Headache: Evaluation by Spectral Analysis of Heart-Rate Fluctuations

Cephalalgia ◽  
1995 ◽  
Vol 15 (6) ◽  
pp. 504-510 ◽  
Author(s):  
M De Marinis ◽  
S Strano ◽  
M Granata ◽  
C Urani ◽  
S Lino ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Spectral Analysis ◽  
Cluster Headache ◽  
Low Frequency ◽  
Sympathetic Activation ◽  
Autonomic Balance ◽  
Spectral Parameters ◽  
Rate Fluctuation ◽  
Head Up Tilt

Twenty-four hour ECG Holter and blood-pressure monitorings were performed in eight patients suffering from cluster headache. Spectral analysis of heart-rate fluctuation was used to assess the autonomic balance under basal conditions, after head-up tilt, and during a spontaneous attack. Normal autonomic balance was found at rest and during sympathetic activation obtained with head-up tilt in the interparoxysmal period. Before the onset of headache, an increase in the low-frequency (LF) component of the power spectrum was apparent in all patients. This sign of sympathetic activation was followed by an increase in the high-frequency (HF) component that developed about 2000 beats after the onset of headache and rapidly overcame the LF component until the end of pain. Significant differences were found when comparing the spectral parameters [total spectral values (TP), power of the LF and HF components and LF/HF ratio] obtained before, during and after headache. During the attack, blood pressure increased and heart rate decreased in all subjects. There appears to be a primary activation of both sympathetic and parasympathetic functions in cluster headache attacks. The sympathetic component seems to be involved mostly in the development of the attack, whereas the parasympathetic activation seems to occur, following the onset of the attack, independently of the pain.

scholarly journals Nonlinear effects of respiration on the crosstalk between cardiovascular and cerebrovascular control systems

2016 ◽  
Vol 374 (2067) ◽  
pp. 20150179 ◽  
Author(s):  
Vlasta Bari ◽  
Andrea Marchi ◽  
Beatrice De Maria ◽  
Gianluca Rossato ◽  
Giandomenico Nollo ◽  
...  
Keyword(s):  
Control Systems ◽  
Cerebral Blood Flow Velocity ◽  
Nonlinear Effects ◽  
Tilt Test ◽  
Control Mechanisms ◽  
Heart Period ◽  
Regulatory Systems ◽  
Head Up Tilt ◽  
Head Up Tilt Test ◽  
The Impact

Cardiovascular and cerebrovascular regulatory systems are vital control mechanisms responsible for guaranteeing homeostasis and are affected by respiration. This work proposes the investigation of cardiovascular and cerebrovascular control systems and the nonlinear influences of respiration on both regulations through joint symbolic analysis (JSA), conditioned or unconditioned on respiration. Interactions between cardiovascular and cerebrovascular regulatory systems were evaluated as well by performing correlation analysis between JSA indexes describing the two control systems. Heart period, systolic and mean arterial pressure, mean cerebral blood flow velocity and respiration were acquired on a beat-to-beat basis in 13 subjects experiencing recurrent syncope episodes (SYNC) and 13 healthy individuals (non-SYNC) in supine resting condition and during head-up tilt test at 60° (TILT). Results showed that JSA distinguished conditions and groups, whereas time domain parameters detected only the effect of TILT. Respiration affected cardiovascular and cerebrovascular regulatory systems in a nonlinear way and was able to modulate the interactions between the two control systems with different outcome in non-SYNC and SYNC groups, thus suggesting that the analysis of the impact of respiration on cardiovascular and cerebrovascular regulatory systems might improve our understanding of the mechanisms underpinning the development of postural-related syncope.

Differential effects of acute hypoxia and high altitude on cerebral blood flow velocity and dynamic cerebral autoregulation: alterations with hyperoxia

2008 ◽  
Vol 104 (2) ◽  
pp. 490-498 ◽  
Author(s):  
Philip N. Ainslie ◽  
Shigehiko Ogoh ◽  
Katie Burgess ◽  
Leo Celi ◽  
Ken McGrattan ◽  
...  
Keyword(s):  
Blood Flow ◽  
Transfer Function ◽  
High Altitude ◽  
Blood Flow Velocity ◽  
Cerebral Autoregulation ◽  
Acute Hypoxia ◽  
Low Frequency ◽  
Frequency Range ◽  
Transfer Function Gain ◽  
Dynamic Cerebral Autoregulation

We hypothesized that 1) acute severe hypoxia, but not hyperoxia, at sea level would impair dynamic cerebral autoregulation (CA); 2) impairment in CA at high altitude (HA) would be partly restored with hyperoxia; and 3) hyperoxia at HA and would have more influence on blood pressure (BP) and less influence on middle cerebral artery blood flow velocity (MCAv). In healthy volunteers, BP and MCAv were measured continuously during normoxia and in acute hypoxia (inspired O2 fraction = 0.12 and 0.10, respectively; n = 10) or hyperoxia (inspired O2 fraction, 1.0; n = 12). Dynamic CA was assessed using transfer-function gain, phase, and coherence between mean BP and MCAv. Arterial blood gases were also obtained. In matched volunteers, the same variables were measured during air breathing and hyperoxia at low altitude (LA; 1,400 m) and after 1–2 days after arrival at HA (∼5,400 m, n = 10). In acute hypoxia and hyperoxia, BP was unchanged whereas it was decreased during hyperoxia at HA (−11 ± 4%; P < 0.05 vs. LA). MCAv was unchanged during acute hypoxia and at HA; however, acute hyperoxia caused MCAv to fall to a greater extent than at HA (−12 ± 3 vs. −5 ± 4%, respectively; P < 0.05). Whereas CA was unchanged in hyperoxia, gain in the low-frequency range was reduced during acute hypoxia, indicating improvement in CA. In contrast, HA was associated with elevations in transfer-function gain in the very low- and low-frequency range, indicating CA impairment; hyperoxia lowered these elevations by ∼50% ( P < 0.05). Findings indicate that hyperoxia at HA can partially improve CA and lower BP, with little effect on MCAv.

Information Transfer through the Spontaneous Baroreflex in Healthy Humans

2010 ◽  
Vol 49 (05) ◽  
pp. 506-510 ◽  
Author(s):  
A. M. Catai ◽  
A. C. M. Takahashi ◽  
V. Magagnin ◽  
T. Bassani ◽  
E. Tobaldini ◽  
...  
Keyword(s):  
Arterial Pressure ◽  
Information Transfer ◽  
Function Analysis ◽  
Systolic Arterial Pressure ◽  
Heart Period ◽  
Uniform Quantization ◽  
Transfer Function Analysis ◽  
Head Up Tilt ◽  
Spontaneous Baroreflex

Summary Objectives: This study assesses the information transfer through the spontaneous baroreflex (i.e. through the pathway linking systolic arterial pressure to heart period) during an experimental condition soliciting baroreflex (i.e. head-up tilt). Methods: The information transfer was calculated as the conditional entropy of heart period given systolic arterial pressure using a mutual neighbor approach and uniform quantization. The information transfer was monitored as a function of the forecasting time k. Results: We found that during head-up tilt the information transfer at k = 0 decreased but the rate of rise of information transfer as a function of k was faster. Conclusions: We suggest that the characterization of the information transfer from systolic arterial pressure to heart period might complement the traditional characterization of the spontaneous baroreflex based on transfer function analysis.

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