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

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.

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Information Transfer through the Spontaneous Baroreflex in Healthy Humans

Methods of Information in Medicine ◽

10.3414/me09-02-0036 ◽

2010 ◽

Vol 49 (05) ◽

pp. 506-510 ◽

Cited By ~ 7

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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Short-term complexity indexes of heart period and systolic arterial pressure variabilities provide complementary information

Journal of Applied Physiology ◽

10.1152/japplphysiol.00755.2012 ◽

2012 ◽

Vol 113 (12) ◽

pp. 1810-1820 ◽

Cited By ~ 52

Author(s):

A. Porta ◽

P. Castiglioni ◽

M. Di Rienzo ◽

V. Bari ◽

T. Bassani ◽

...

Keyword(s):

Arterial Pressure ◽

Systolic Arterial Pressure ◽

Adrenergic Blockade ◽

Sympathetic Blockade ◽

Heart Period ◽

Complementary Information ◽

Beta Adrenergic ◽

Orthostatic Challenge ◽

Vagal Blockade ◽

Head Up Tilt

It is unclear whether the complexity of the variability of the systolic arterial pressure (SAP) provides complementary information to that of the heart period (HP). The complexity of HP and SAP variabilities was assessed from short beat-to-beat recordings (i.e., 256 cardiac beats). The evaluation was made during a pharmacological protocol that induced vagal blockade with atropine or a sympathetic blockade (beta-adrenergic blockade with propranolol or central sympathetic blockade with clonidine) alone or in combination, during a graded head-up tilt, and in patients with Parkinson's disease (PD) without orthostatic hypotension undergoing orthostatic challenge. Complexity was quantified according to the mean square prediction error (MSPE) derived from univariate autoregressive (AR) and multivariate AR (MAR) models. We found that: 1) MSPEMAR did not provide additional information to that of MSPEAR; 2) SAP variability was less complex than that of HP; 3) because HP complexity was reduced by either vagal blockade or vagal withdrawal induced by head-up tilt and was unaffected by beta-adrenergic blockade, HP was under vagal control; 4) because SAP complexity was increased by central sympathetic blockade and was unmodified by either vagal blockade or vagal withdrawal induced by head-up tilt, SAP was under sympathetic control; 5) SAP complexity was increased in patients with PD; and 6) during orthostatic challenge, the complexity of both HP and SAP variabilities in patients with PD remained high, thus indicating both vagal and sympathetic impairments. Complexity indexes derived from short HP and SAP beat-to-beat series provide complementary information and are helpful in detecting early autonomic dysfunction in patients with PD well before circulatory symptoms become noticeable.

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Causal relationships between heart period and systolic arterial pressure during graded head-up tilt

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00553.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. R378-R386 ◽

Cited By ~ 72

Author(s):

Alberto Porta ◽

Aparecida M. Catai ◽

Anielle C. M. Takahashi ◽

Valentina Magagnin ◽

Tito Bassani ◽

...

Keyword(s):

Arterial Pressure ◽

Causal Relation ◽

Systolic Arterial Pressure ◽

Causal Link ◽

Heart Period ◽

Reverse Causality ◽

Tilt Table ◽

Baroreflex Control ◽

Healthy Humans ◽

Head Up Tilt

In physiological conditions, heart period (HP) affects systolic arterial pressure (SAP) through diastolic runoff and Starling's law, but, the reverse relation also holds as a result of the continuous action of baroreflex control. The prevailing mechanism sets the dominant temporal direction in the HP-SAP interactions (i.e., causality). We exploited cross-conditional entropy to assess HP-SAP causality. A traditional approach based on phases was applied for comparison. The ability of the approach to detect the lack of causal link from SAP to HP was assessed on 8 short-term (STHT) and 11 long-term heart transplant (LTHT) recipients (i.e., less than and more than 2 yr after transplantation, respectively). In addition, spontaneous HP and SAP variabilities were extracted from 17 healthy humans (ages 21–36 yr, median age 29 yr; 9 females) at rest and during graded head-up tilt. The tilt table inclinations ranged from 15 to 75° and were changed in steps of 15°. All subjects underwent recordings at every step in random order. The approach detected the lack of causal relation from SAP to HP in STHT recipients and the gradual restoration of the causal link from SAP to HP with time after transplantation in the LTHT recipients. The head-up tilt protocol induced the progressive shift from the prevalent causal direction from HP to SAP to the reverse causality (i.e., from SAP to HP) with tilt table inclination in healthy subjects. Transformation of phases into time shifts and comparison with baroreflex latency supported this conclusion. The proposed approach is highly efficient because it does not require the knowledge of baroreflex latency. The dependence of causality on tilt table inclination suggests that “spontaneous” baroreflex sensitivity estimated using noncausal methods (e.g., spectral and cross-spectral approaches) is more reliable at the highest tilt table inclinations.

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An Empirical Mode Decomposition Approach to Assess the Strength of Heart Period-Systolic Arterial Pressure Variability Interactions

2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC) ◽

10.1109/embc44109.2020.9175647 ◽

2020 ◽

Author(s):

Vlasta Bari ◽

Beatrice Cairo ◽

Beatrice De Maria ◽

Davide Tonon ◽

Gianluca Rossato ◽

...

Keyword(s):

Arterial Pressure ◽

Empirical Mode Decomposition ◽

Systolic Arterial Pressure ◽

Heart Period ◽

Decomposition Approach ◽

Mode Decomposition ◽

Arterial Pressure Variability

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Causal coherence detects causality in the closed loop relationship between heart period and systolic arterial pressure variability series

Computers in Cardiology 2001. Vol.28 (Cat. No.01CH37287) ◽

10.1109/cic.2001.977659 ◽

2002 ◽

Author(s):

A. Porta ◽

R. Furlan ◽

A. Malliani ◽

P. van de Borne

Keyword(s):

Arterial Pressure ◽

Closed Loop ◽

Systolic Arterial Pressure ◽

Heart Period ◽

Arterial Pressure Variability ◽

Causal Coherence

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Exploring directionality in spontaneous heart period and systolic pressure variability interactions in humans: implications in the evaluation of baroreflex gain

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00594.2004 ◽

2005 ◽

Vol 288 (4) ◽

pp. H1777-H1785 ◽

Cited By ~ 78

Author(s):

Giandomenico Nollo ◽

Luca Faes ◽

Alberto Porta ◽

Renzo Antolini ◽

Flavia Ravelli

Keyword(s):

Spectral Analysis ◽

Spectral Component ◽

Systolic Pressure ◽

Low Frequency ◽

Systolic Arterial Pressure ◽

Phase Lag ◽

Healthy Humans ◽

Head Up Tilt ◽

Causal Approach ◽

Young Subjects

Although in physiological conditions RR interval and systolic arterial pressure (SAP) are likely to interact in a closed loop, the traditional cross-spectral analysis cannot distinguish feedback (FB) from feedforward (FF) influences. In this study, a causal approach was applied for calculating the coherence from SAP to RR ( Ks-r) and from RR to SAP ( Kr-s) and the gain and phase of the baroreflex transfer function. The method was applied, compared with the noncausal one, to RR and SAP series taken from 15 healthy young subjects in the supine position and after passive head-up tilt. For the low frequency (0.04–0.15 Hz) spectral component, the enhanced FF coupling ( Kr-s = 0.59 ± 0.21, significant in 14 subjects) and the blunted FB coupling ( Ks-r = 0.17 ± 0.17, significant in 4 subjects) found at rest indicated the prevalence of nonbaroreflex mechanisms. The tilt maneuver recovered FB influences ( Ks-r = 0.47 ± 0.16, significant in 14 subjects), which were stronger than FF interactions ( Ks-r = 0.34 ± 0.19, significant in 9 subjects). At the respiratory frequency, the RR-SAP regulation was balanced at rest ( Ks-r = 0.30 ± 0.18 and Kr-s = 0.29 ± 0.20, significant in 11 and 8 subjects) and shifted toward FB mechanisms after tilt ( Ks-r = 0.35 ± 0.19 and Kr-s = 0.19 ± 0.11, significant in 14 and 8 subjects). The causal baroreflex gain estimates were always lower than the corresponding noncausal values and decreased significantly from rest to tilt in both frequency bands. The tilt-induced increase of the phase lag from SAP to RR suggested a shift from vagal to sympathetic modulation. Thus the importance of nonbaroreflex interactions pointed out the necessity of accounting for causality in the cross-spectral analysis of the interactions between cardiovascular variables in healthy humans.

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