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ABSTRACT: Underlying mechanisms of increased pressor responses to stress in Blacks are poorly understood. Cardiovascular regulation of normotensive Black (n=43) and Caucasian (n=90) Africans was studied during a cold pressor and color-word conflict test. Autonomic evaluation was performed by spectral analysis. Higher diastolic pressor and heart rate responses to the cold pressor test were observed in Black compared to Caucasian Africans. Autonomic efferent outflow to stress was comparable between groups. Transient downregulation of baroreflex during stress was evident in Blacks but not in Caucasians. Greater diastolic pressor responses were related to a higher cardiac reactivity, a baroreflex desensitization, and higher stress perception in Black Africans. Thus, increased stress perception may facilitate cardiac and diastolic hyperreactivity, indirectly affecting baroreflex function in Black Africans.
Psychophysiology 12/2011; 49(4):454-61. · 3.29 Impact Factor
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ABSTRACT: Differences in spontaneous and drug-induced baroreflex sensitivity (BRS) have been attributed to its different operating ranges. The current study attempted to compare BRS estimates during cardiovascular steady-state and pharmacologically stimulation using an innovative algorithm for dynamic determination of baroreflex gain.
Forty-five volunteers underwent the modified Oxford maneuver in supine and 60° tilted position with blood pressure and heart rate being continuously recorded. Drug-induced BRS-estimates were calculated from data obtained by bolus injections of nitroprusside and phenylephrine. Spontaneous indices were derived from data obtained during rest (stationary) and under pharmacological stimulation (non-stationary) using the algorithm of trigonometric regressive spectral analysis (TRS). Spontaneous and drug-induced BRS values were significantly correlated and display directionally similar changes under different situations. Using the Bland-Altman method, systematic differences between spontaneous and drug-induced estimates were found and revealed that the discrepancy can be as large as the gain itself. Fixed bias was not evident with ordinary least products regression. The correlation and agreement between the estimates increased significantly when BRS was calculated by TRS in non-stationary mode during the drug injection period. TRS-BRS significantly increased during phenylephrine and decreased under nitroprusside.
The TRS analysis provides a reliable, non-invasive assessment of human BRS not only under static steady state conditions, but also during pharmacological perturbation of the cardiovascular system.
PLoS ONE 01/2011; 6(3):e18061. · 4.09 Impact Factor
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ABSTRACT: Hypotensive episodes are relatively frequent adverse effects during LDL apheresis. To evaluate the impact of LDL apheresis on autonomic cardiovascular control we investigated hypercholesterolemic patients before and after a single LDL apheresis in comparison to an age-matched control group.
We continuously recorded systemic arterial blood pressure, electrocardiogram and respiration in 21 hypercholesterolemic patients (57 ± 15 years) on regular LDL apheresis treatment and 22 healthy control subjects (56 ± 4 years) during cardiovascular autonomic testing (metronomic breathing, Valsalva manoeuvre, head-up tilt). Baroreflex sensitivity and frequency spectra of R-R intervals and systolic blood pressure were evaluated by trigonometric regressive spectral analysis.
Hypercholesterolemic patients had reduced resting baroreflex sensitivity and high-frequency power of heart rate variability compared to controls. Consequently, there was a sympathetic predominance of heart rate modulation reflected by increased ratio of low-to-high frequency power of R-R intervals. Cardiovascular stimulation failed to adequately activate baroreflex mechanisms before LDL apheresis. After LDL apheresis, the parasympathetic response to cardiovascular stimulation improved and sympathetic outflow to peripheral vasculature was reduced. Baroreflex sensitivity remained low.
Hypercholesterolemic patients on regular LDL apheresis treatment have significant autonomic dysfunction. A single LDL apheresis does not evoke sympathetic overactivation but improved deranged cardiovagal heart rate modulation in hypercholesterolemia.
Atherosclerosis 11/2010; 213(1):212-7. · 3.79 Impact Factor
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ABSTRACT: Carotid endarterectomy (CEA) is the first-line treatment in severe carotid stenosis to prevent stroke. Because of methodological limitations, the acute impact of CEA on baroreflex function and cerebral autoregulation is not well defined and was therefore investigated by applying a novel algorithm.
Systemic arterial blood pressure, ECG and respiration during metronomic breathing and Valsalva maneuver were continuously recorded in 18 patients with carotid stenosis before and after CEA, and in 10 healthy controls. Baroreflex sensitivity, frequency spectra of RR intervals and indices for cerebral autoregulation were evaluated by trigonometric regressive spectral analysis. Compared with the controls, patients had impaired baroreflex sensitivity. Baroreflex sensitivity and frequency spectra were not changed by CEA. Cerebral autoregulation of patients with carotid stenosis as calculated by phase shift was reduced compared with controls but it improved significantly after CEA. Improvement of cerebral autoregulation was independent of changes in cerebral blood flow velocity.
Baroreflex sensitivity and cerebral autoregulation are impaired in patients with carotid stenosis, conferring a high stroke risk. CEA improves cerebral autoregulation, but does not affect baroreflex sensitivity. For further risk reduction, interventional approaches targeting baroreflex function need to be considered.
Circulation Journal 10/2010; 74(10):2139-45. · 3.77 Impact Factor
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ABSTRACT: The assessment of baroreflex sensitivity (BRS) has emerged as prognostic tool in cardiology. Although available computer-assisted methods, measuring spontaneous fluctuations of heart rate and blood pressure in the time and frequency domain are easily applicable, they do not allow for quantification of BRS during cardiovascular adaption processes. This, however, seems an essential criterion for clinical application. We evaluated a novel algorithm based on trigonometric regression regarding its ability to map dynamic changes in BRS and autonomic tone during cardiovascular provocation in relation to gender and age.
We continuously recorded systemic arterial pressure, electrocardiogram and respiration in 23 young subjects (25+/-2 years) and 22 middle-aged subjects (56+/-4 years) during cardiovascular autonomic testing (metronomic breathing, Valsalva manoeuvre, head-up tilt). Baroreflex- and spectral analysis was performed using the algorithm of trigonometric regressive spectral analysis. There was an age-related decline in spontaneous BRS and high frequency oscillations of RR intervals. Changes in autonomic tone evoked by cardiovascular provocation were observed as shifts in the ratio of low to high frequency oscillations of RR intervals and blood pressure. Respiration at 0.1 Hz elicited an increase in BRS while head-up tilt and Valsalva manoeuvre resulted in a downregulation of BRS. The extent of autonomic adaption was in general more pronounced in young individuals and declined stronger with age in women than in men.
The trigonometric regressive spectral analysis reliably maps age- and gender-related differences in baroreflex- and autonomic function and is able to describe adaption processes of baroreceptor circuit during cardiovascular stimulation. Hence, this novel algorithm may be a useful screening tool to detect abnormalities in cardiovascular adaption processes even when resting values appear to be normal.
PLoS ONE 01/2010; 5(8):e12187. · 4.09 Impact Factor
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Constanze Friedrich, Heinz Rüdiger,
Claudia Schmidt,
Birgit Herting,
Silke Prieur,
Susann Junghanns,
Katherine Schweitzer,
Christoph Globas,
Ludger Schöls,
Daniela Berg,
Heinz Reichmann,
Tjalf Ziemssen
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ABSTRACT: Autonomic dysfunction has been frequently demonstrated in patients with extrapyramidal diseases by cardiovascular autonomic testing. In addition to classical testing, we applied the more detailed baroreflex and spectral analysis on three traditional cardiovascular tests in this study to get additional information on autonomic outflow. We recorded continuously blood pressure, electrocardiogram, and respiration in 35 patients with multiple system atrophy, 32 patients with progressive supranuclear palsy, 46 patients with idiopathic Parkinson's disease and in 27 corresponding healthy subjects during cardiovascular autonomic testing (metronomic breathing, Valsalva manoeuvre, head-up tilt). Baroreflex and spectral analyses were performed by using trigonometric regressive spectral analysis between and during the manoeuvres. Consistent with previous interpretations, our data showed an increase of sympathetic activity in head-up tilt and Valsalva test in healthy controls. This sympathetic activity was significantly decreased in patients with typical and atypical Parkinson syndromes. Significant modulation of baroreflex activity could be observed especially during metronomic breathing; again it was significantly lower in all patient groups. Baroreflex and spectral parameters could not only differentiate between patients and healthy controls, but also differentiate between clinically symptomatic (with autonomic dysfunction as eg. orthostatic hypotension) and asymptomatic patients. In conclusion, our approach allows the evaluation of autonomic variability during short and nonstationary periods of time and may constitute a useful advance in the assessment of autonomic function in both physiological and pathological conditions.
Movement Disorders 12/2009; 25(3):315-24. · 4.51 Impact Factor
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ABSTRACT: Increased daytime blood pressure and reduced nocturnal dipping can already be found in children with type 1 diabetes mellitus. We hypothesized that impaired baroreflex sensitivity can cause this abnormal blood pressure behavior in children and adolescents with type 1 diabetes, reflecting an early stage of diabetic autonomic neuropathy.
In the present study, we monitored beat-to-beat blood pressure and pulse interval non-invasively with portapres in 38 patients with type 1 diabetes (7-18 yr) and 14 non-diabetic subjects (5-17 yr). The Trigonometric Regressive Spectral Analysis was used to assign spontaneous oscillations of blood pressure and pulse interval to defined frequency bands between 0.003 and 1.0 Hz and to calculate baroreflex sensitivity. Correlations with diabetes-specific data like hemoglobin A1c (HbA1c) and with 24-h blood pressure measurements were calculated.
The diabetic subjects displayed significantly less variance of blood pressure and pulse interval in the high frequency (HF) bands and a lower BRS. BRS decreased with higher HbA1c and daily insulin dose. We also saw significant changes in spectral variance of blood pressure and pulse interval with these parameters. Patients with higher sympathetic activity (LF/HF-ratio) during daytime measurements displayed more nocturnal dipping.
Our data evidence impaired baroreflex sensitivity in children and adolescents with type 1 diabetes mellitus. We suggest spectral analysis of spontaneous blood pressure and pulse interval oscillations during night sleep to further pursue the role of baroreflex sensitivity in the etiology of the non-dipping phenomenon in diabetic patients.
Pediatric Diabetes 02/2009; 10(4):255-63. · 2.16 Impact Factor
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ABSTRACT: ZusammenfassungFragestellung Zur erforderlichen Genauigkeit der automatisierten Registrierung der RR-Intervalle gibt es unterschiedliche Aussagen. Es soll gezeigt werden, dass Abtastfrequenzen von 100 Hz bis zu 40 Hz keine signifikanten Beeintrchtigungen der Spektralanalysen von RR-Intervallen darstellen.Patienten und Methodik Es wurden 30 Patienten im Schlaflabor mit einer EKG-Abtastung von 100 Hz mit dem Alice 3.0 System untersucht. Da mit diesem System auch Abtastfrequenzen von 40 Hz möglich sind, wurden die Auswirkungen beider unterschiedlichen Abtastfrequenzen auf eine nachfolgende Spektralanalyse untersucht. Die Untersuchung wurde für die Gesamtpopulation (N = 30) sowie für zwei unterschiedliche Mittelwertgruppen (RR > 900 ms; n = 15 und RR < 900 ms; n = 15) durchgeführt. Die Abtastwiederholung erfolgte mittels Simulationstechnik.Ergebnisse Die mittlere Lnge der RR-Intervalle wirkt sich auf die spektralen Parameter unterschiedlich aus. Zeitbereichsparameter wurden kaum verndert. Unterschiede > 5 % zwischen beiden Abtastfrequenzen gab es nur im sehr hohen Frequenzband > 0.40 Hz (UHF) für kurze mittlere RR-Intervalle. Alle anderen Abweichungen waren in der Größenordnung von 1–3 %.Schlussfolgerung Mittels Simulation konnten nur geringe Beeintrchtigungen von Spektralanalysen gefunden werden. Entscheidend ist eine mathematisch korrekte Analysemethodik. Weitere Vergleiche mit gleichzeitig unterschiedlichen Abtastfrequenzen sind notwendig um die Ergebnisse dieser mathematischen Simulationen unter echten Ableitungsbedingungen zu besttigen.SummaryQuestion of the study There are differing opinions regarding the accuracy required of sampling frequencies in ECG signals. The question of this study was whether sampling frequencies of 100 Hz or 40 Hz would significantly influence the results of spectral analysis of R-R intervals.Patients and methods Thirty subjects underwent polysomnographic recordings in the sleep laboratory, sampled at a frequency of 100 Hz using the Alice 3.0 system. Two different sampling frequencies were used to assess the effects on a subsequent spectral analysis of R-R intervals. Repetition using a different sampling frequency was performed with a simulation technique. The study was performed on the total group (N = 30) and on two different subgroups (mean R-R > 900 ms; n = 15 and mean R-R < 900 ms; n = 15), respectively.Results Although different means of R-R intervals influence the following spectral parameters in different ways, there are only small changes in the time domain. Differences > 5% in analyses using two different sampling frequencies was found only in the UHF band (very high frequency band > 0.40 Hz) in time series with short R-R intervals. In LF band and HF band, the differences varied between 1% and 3%.Conclusions Using the simulation technique, we found only small changes in the spectral analysis parameters. The selection of a correct mathematical approach seems to be an important precondition. Additional comparative studies using different sampling frequencies for the same data segment are necessary to confirm these results in real-time conditions.
Somnologie - Schlafforschung und Schlafmedizin 05/2006; 10(2):53 - 60.
