Home About us Contact
|
Home About us Contact | ||
|
|
||
Sympathovagal Balance (sympathovagal + balance)
Selected AbstractsCardiac autonomic function and baroreflex changes following 4 weeks of resistance versus aerobic training in individuals with pre-hypertensionACTA PHYSIOLOGICA, Issue 3 2009S. R. Collier Abstract Aim:, Cardiac autonomic modulation and baroreflex sensitivity (BRS) are altered in individuals with hypertension. Aerobic exercise (AE) training has been shown to improve both measures, yet little is known about the effects of resistance exercise (RE). The purpose of this study was to examine the heart rate variability (HRV) and BRS following 4 weeks of resistance or aerobic training in a population with borderline high blood pressure (BP). Methods:, Twenty-nine mild hypertensives were recruited and randomly assigned to 4 weeks of RE or AE training. Before and after training, resting measures of HRV frequencies and BRS were obtained. Results:, There was a significant decrease in resting systolic BP for both exercise training modes (RE 136 ± 3.0 pre- to 132 ± 3.4 post-training vs. AE 142 ± 4.0 pre- to 137 ± 3.6 mmHg post-training, P = 0.019). Diastolic BP decreased significantly following both exercise training modes (RE 78 ± 1.31 pre to 74 ± 1.1 post vs. AE 80 ± 1.7 pre to 77 ± 1.6 mmHg post, P = 0.002). A significant time by training mode interaction for low frequency : high frequency (HF) ratio (P = 0.017) with AE decreasing the ratio (275.21 ± 67.28 to 161.26 ± 61.49) and RE increasing this ratio (143.73 ± 65.00 to 227.83 ± 59.41). Natural log-transformed (ln) HRV values showed a time-by-training mode interaction for ln HF (P = 0.05) as ln HF increased (4.7 ± 0.38 to 5.4 ± 0.35 ms2) following AE and decreased (5.98 ± 0.37 to 5.76 ± 0.42 ms2) following RE. BRS increased following aerobic training and decreased after resistance training (6.74 ± 1.2 to 7.94 ± 1.3 and 10.44 ± 1.2 to 9.1 ± 1.2 ms mmHg,1 respectively, P = 0.021). Conclusions:, Aerobic exercise improved the autonomic nervous system (increasing vagal tone, reducing sympathovagal balance while increasing BRS) while RE showed no improvements in cardiac autonomic tone and decreased BRS. [source] Heart Rate Variability in Emergency Department Patients with SepsisACADEMIC EMERGENCY MEDICINE, Issue 7 2002Douglas Barnaby MD Abstract Objective: To test the hypothesis that heart rate variability (HRV) can provide an early indication of illness severity among patients presenting to the emergency department (ED) with sepsis. Methods: The authors enrolled a convenience sample of 15 ED patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria for sepsis. Each patient had continuous Holter monitoring performed in the ED. Acute Physiology and Chronic Health II (APACHE II) and Sequential Organ Failure (SOFA) scores were calculated for the day of presentation. Holter tapes obtained in the ED were analyzed off-line to calculate HRV variables for the 5-minute segment with the least artifact and non-sinus beats. These variables were correlated with APACHE II and SOFA scores. Results: LFnu (normalized low-frequency power), an assessment of the relative sympathetic contribution to overall HRV, was correlated with increased illness severity as calculated using APACHE II (r = -0.67, r2= 0.43) and SOFA (r = -0.80, r2= 0.64) scores. LF/HF ratio (low-frequency/high-frequency ratio), a measure of sympathovagal balance, was correlated with the SOFA score [r = -0.54 (95% CI = -0.83 to -0.01), r2= 0.29]. All five patients who required critical care monitoring or ventilatory support or who died during the first 5 days of their hospitalization had LFnu values below 0.5 and LF/HF ratios less than 1.0. None of the patients with measurements greater than these threshold values died or required these interventions during the five days following admission. Conclusions: A single variable, LFnu, which reflects sympathetic modulation of heart rate, accounted for 40-60% of the variance in illness severity scores among patients presenting to the ED with sepsis. HRV, as reflected in LFnu and the LF/HF ratio and measured with a single brief (5-minute) period of monitoring while in the ED, may provide the emergency physician with a readily available, noninvasive, early marker of illness severity. The threshold effect of LFnu and LF/HF in the prediction of early clinical deterioration was an unexpected finding and should be regarded as hypothesis-generating, pending further study. [source] Instant centre frequency at anaesthetic induction , a new way to analyse sympathovagal balance,FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2003Edmundo Pereira De Souza Neto Abstract The instant centre frequency (ICF) of RR interval has been proposed as a global index to analyse the sympathovagal interaction in the heart. The aim of this study was to assess the ICF during anaesthesia to test if it can reliably capture the neural control of the cardiovascular system. Twenty-four ASA II or III patients scheduled for cardiac surgery were included in the study. They were allocated in two groups: control, no treatment (group 1, n = 12), and beta-adrenergic blockade by atenolol (group 2, n = 12). Spectra of pulse interval series were computed with a time,frequency method and they were divided into: very low frequency (VLF, 0.000,0.040 Hz), low frequency (LF, 0.050,0.150 Hz) and high frequency (HF, 0.160,0.500 Hz). Normalized power was obtained by dividing the cumulative power within each frequency band (LF or HF) by the sum of LF and HF; the ratio of LF/HF was also calculated. Instant centre frequency is a time-varying parameter that the evolution along time of the gravity centrum of a local spectrum. All spectral indexes were recorded at the following time points: before induction, after induction and before intubation, during intubation, and after intubation. The atenolol group had lower normalized LF and the LF/HF ratio (P < 0.05) higher HF before induction; and lower LF/HF ratio after induction and before intubation (P < 0.05). The ICF was higher in atenolol group at all times. The ICF shifted towards HF frequency after induction and before intubation and shifted towards LF during intubation in both groups. The autonomic nervous system control on the heart through the interaction of sympathetic and parasympathetic reflex mechanisms could be studied by the ICF. The ICF may assess the autonomic cardiac modulation and may provide useful information for anaesthetic management. [source] Independent Autonomic Modulation of Sinus Node and Ventricular Myocardium in Healthy Young Men During SleepJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000PETER KOWALLIK M.D. Autonomic Modulation of Sinus Node and Ventricle. Introduction. The aim of this study was to investigate whether autonomic modulation of ventricular repolarization may spontaneousiy differ from that of the sinoatrial node. Methods and Results. Onset of P waves. QRS complexes, and the apex and end of T waves were detected heat to heat in high-resolution ECGs from nine healthy young men during the night. There were time-dependent fluctuations in the QT/RR slopes of consecutive 5-minute segments that could not he explained by the mean RR cycle length of the respective segment. Because the variahility found in QT intervals could not be explained hy either possible effects of rate dependence or hysteresis, autonomic effects were obvious. Power speetral analysis was performed for consecutive 5-minute segments of PP and QT techograms. In a given subject. trends in the time course of low-frequency (LF) and high-frequency (HF) power in PP and QT often were similar, but they were quite different at other times. The mean LF/HF ratio for QTend (0.75 ± 0.1) was different from that of PP (1.8 ± 0.2; P = 0.002), indicating differences in sympathovagal balance at the different anatomic sites. Furthermore, at a given mean heart rate, averaged QT intervals were different on a time scale of several minutes to hours. The QT/RR slope of 5-minute segments correlated significantly with the HF power of QT variability but not with that of PP variability, indicating effects of the autonomic nervous system on ventricular action potential restitution. Conclusion. These differences demonstrate that changes in sinus node automaticity are not necessarily indicative of the autonomic control of ventricular myocardium. (J Cardiavasc Electrophysiol, Vol. II, pp. 1063-1070. October 2000) [source] Effects of audio stimulation on gastric myoelectrical activity and sympathovagal balance in healthy adolescents and adultsJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 1 2008Dennis D Chen Abstract Aim:, The primary aim of this study was to investigate the effects of different audio stimulations on gastric myoelectrical activity and sympathovagal balance in adolescents compared with adults. Methods:, The study was performed in 11 adults and 12 adolescents. Each subject underwent two sessions, one for classical music, and the other for noise. Each session consisted of 30 min of baseline, 30 min of fasting audio stimulation, a test meal, 30 min of fed audio stimulation, and 30 min of recovery. Electrocardiogram and electrogastrogram were both recorded throughout each session. Results:, (i) In the fasting state, both classical music and noise impaired gastric slow wave activity in adolescents. In adults, noise had no effects while classical music moderately improved slow wave rhythmicity. (ii) In the fed state, neither noise nor music had any effects on gastric slow waves. (iii) In the fasting state, both noise and music increased the sympathovagal balance in adolescents; in adults only noise had such an effect. (iv) The test meal increased the sympathovagal balance in all groups. Conclusions:, Gastric slow waves and the sympathovagal balance are more strongly affected by audio stimulation in adolescents than in adults. The test meal normalizes the audio stimulation-induced differences between the groups. [source] Sympathovagal effects of spinal anaesthesia with intrathecal or intravenous fentanyl assessed by heart rate variabilityACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2009Y. FUJIWARA Background: Although many investigators previously reported the sympathovagal effect of spinal anaesthesia, there is no information about the sympathovagal effects of supplementation with fentanyl. The aim of this study was to evaluate the sympathovagal effects of intrathecal or intravenous fentanyl added to spinal anaesthesia. Methods: One hundred and twenty patients undergoing elective transurethral surgery under spinal anaesthesia were randomly allocated to receive intrathecally either isobaric bupivacaine alone (Group B), bupivacaine supplemented with intrathecal (Group Ft) or with intravenous fentanyl (Group Fv). Heart rate variability was estimated using the MemCalc method (Tarawa, Suwa Trust, Japan) before and after spinal anaesthesia. Results: In all groups, spinal anaesthesia significantly decreased low frequency/high frequency (LF/HF) as a marker of sympathovagal balance. However, patients in Group B with a low block height developed a marked increase in LF/HF after spinal anaesthesia, which was attenuated in Group Ft. Meanwhile, intravenous fentanyl did not attenuate this response. Conclusion: We conclude that sympathetic activation observed in patients with a low block height was attenuated by intrathecal fentanyl but not by intravenous fentanyl. [source] QT Interval Dispersion and Cardiac Sympathovagal Balance Shift in Rats With Acute Ethanol WithdrawalALCOHOLISM, Issue 2 2010Seiko Shirafuji Background:, Dysregulation of autonomic nervous system function and impaired homogeneity of myocardial repolarization are 2 important mechanisms for the genesis of ventricular arrhythmias in nonalcoholic subjects. Our previous study suggested that acute ethanol withdrawal promoted the shift of cardiac sympathovagal balance toward sympathetic predominance and reduced the vagal tone, which were related to a higher incidence of ventricular arrhythmia and related death. However, the homogeneity of myocardial repolarization and its relation with the cardiac sympathovagal balance are unknown, especially in alcoholic subjects. The aim of the present study was to clarify these points. Methods:, Male Wistar rats were treated with a continuous ethanol liquid diet for 49 days, and then subjected to 1-day withdrawal and 1-day withdrawal with 7-day carvedilol (can block the sympathetic nervous system completely via ,1, ,2, and , adrenergic receptors) pretreatment. The cardiac sympathovagal balance and homogeneity of myocardial repolarization were evaluated based on the heart rate variability (HRV) and QT interval dispersion (QTd: dynamic changes in QT interval duration). Results:, The increase in QTd was observed only in rats at 1-day withdrawal, but not in nonalcoholic, continuous ethanol intake, and 1-day withdrawal with 7-day carvedilol pretreatment rats. At 1-day withdrawal, the low-frequency power/high-frequency power (LF/HF) ratio in HRV was elevated and correlated with the QTd. The increased QTd and elevated LF/HF ratio were normalized by the 7-day carvedilol pretreatment in rats at 1-day ethanol withdrawal. Conclusions:, In rats with an abrupt termination of the chronic continuous ethanol intake, the homogeneity of myocardial repolarization impaired and correlated with the cardiac sympathovagal balance. Carvedilol pretreatment is associated with a reduction in both the QTd and LF/HF ratio, raising the possibility that the cardiac sympathovagal balance shift may be responsible for the impaired homogeneity of myocardial repolarization, and that ,-blocker pretreatment may decrease the mortality risk during alcoholic withdrawal. [source] Abrupt Termination of an Ethanol Regimen Provokes Ventricular Arrhythmia and Enhances Susceptibility to the Arrhythmogenic Effects of Epinephrine in RatsALCOHOLISM, Issue 2010Jinyao Liu Background:, Pathologists examining victims of sudden unexpected death encounter alcoholics more often than expected; alcohol may play a role in sudden arrhythmic death. Here we determine whether a pattern of alcohol consumption, chronic ethanol intake, and withdrawal increases the incidence of malignant ventricular arrhythmia and modulates susceptibility to the arrhythmogenic potential of sympathetic stimulation from an epinephrine test in rats. Methods:, Male Wistar rats were treated with a continuous ethanol liquid diet for 7 weeks, and then subjected to 1-day withdrawal or 21-day abstinence. Ventricular ectopy was evaluated by 24-hour electrocardiographic telemetry recording; whole-body sympathetic activation, cardiac sympathovagal balance, and susceptibility to ventricular arrhythmia induced by sympathetic stimulation were evaluated based on blood noradrenalin metabolite concentrations, heart rate variability, and a 3-step epinephrine test. Results:, Ventricular arrhythmia and related death were observed only in rats at 1 day of withdrawal, but not in nonalcoholic, continuous ethanol intake or 21-day abstinence rats. One-day withdrawal after a 7-week continuous ethanol regimen elevated circulating noradrenalin metabolite levels and induced cardiac sympathovagal imbalance. Deaths related to the epinephrine test and ventricular arrhythmia induced by low doses of epinephrine were observed only in 1-day withdrawal rats. However, all anomalies were normalized by 21-day abstinence. Conclusions:, Abrupt termination of a 7-week continuous ethanol regimen is sufficient to enhance the whole-body sympathetic activation and cardiac sympathovagal imbalance that contribute to ventricular arrhythmia and sudden death in alcoholic rats. Those providing medical care for alcoholics, including in cases of legal imprisonment, should be aware of the possibility of enhanced susceptibility to sudden arrhythmic death due to the abrupt termination of a chronic ethanol regimen. [source] Assessment of autonomic cardiovascular changes associated with recovery from anaesthesia in children: a study using spectral analysis of blood pressure and heart rate variabilityPEDIATRIC ANESTHESIA, Issue 6 2000ISABELLE CONSTANT MD PhD Recovery from anaesthesia is associated with large changes in cardiovascular autonomic activity, which are poorly documented in children. This study was undertaken to investigate the cardiovascular autonomic activity in anaesthetized and recovering children, using a noninvasive approach based on spectral analysis of heart rate (HR) and blood pressure (BP) variability. Ten children (aged 5,13 years) undergoing major surgery were studied. Continuous HR and BP were recorded using a noninvasive device during deep anaesthesia and recovery. Spectral analysis was used to determine the main oscillatory components of HR and BP signals. For each power spectrum, the frequency components were identified as follows (i): the low frequency (LF) component (0.04,0.14 Hz) both parasympathetically and sympathetically mediated for HR and corresponding to vasomotor sympathetic modulation for BP; and (ii) the high frequency (HF) component (0.2,0.6 Hz) parasympathetically mediated for HR, and reflecting mechanical influence of ventilation on cardiac output for BP. In addition, the LF : HF ratio for HR, reflecting the cardiac sympathovagal balance, was calculated. Under deep anaesthesia, HR variability and BP variability were very low and mainly due to mechanical influence of intermittent positive pressure ventilation. Conversely, the recovery period was associated with a marked increase of HR and BP overall variability. Compared to anaesthesia, spectral analysis of HR and BP revealed that the LF component of BP and HR spectra increased 40-fold during recovery; the LF : HF ratio of HR was also increased during recovery (0.1 ± 0.1 versus 1.3 ± 1.2, P=0.008). The results of this study demonstrate that the recovery period is associated with an increase of cardiovascular sympathetic drive in children after major surgery. [source] Heart Rate Variability in Obstructive Sleep Apnea: A Prospective Study and Frequency Domain AnalysisANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2003Lorne J Gula F.R.C.P.C. Background: Cyclic variation of the heart rate is observed during apneic spells in obstructive sleep apnea (OSA). We hypothesized that autonomic changes would affect frequency-domain measures of heart rate variability (HRV). Methods: We studied 20 patients (15 men, 5 women, mean age 47.2 ± 12.2 years) with suspected OSA undergoing overnight polysomnography, and five patients (4 men, 1 woman, mean age 49.2 ± 8.6 years) with recently diagnosed sleep apnea undergoing polysomnography while wearing continuous positive airway pressure (CPAP). Holter monitors were applied during sleep studies and data were analyzed in 5-minute blocks over the course of the night. Using spectral analysis, low frequency (LF) and high frequency (HF) powers were calculated for each interval. Overall mean and standard deviation (SD) for LF power, HF power, and the LF:HF ratio were recorded for each patient. Comparisons were made between patients with severe OSA (apnea hypopnea index (AHI) > 30, n = 8), moderate OSA (AHI 1,30, n = 5), without OSA (AHI < 10, n = 7), and patients wearing CPAP (n = 5). Results: Assessment of overnight LF or HF power revealed no significant difference between the four groups. The LF:HF ratio, which represents sympathovagal balance, was higher among those with moderate disease compared to normals and those with severe OSA (both P = 0.037). The standard deviation of the LF:HF ratio was higher among those with moderate disease compared to normals (P = 0.0064) and those with severe OSA (P = 0.0006). OSA patients receiving CPAP behaved like patients with moderate OSA, with increased SD of the LF:HF ratio. Conclusions: The observed changes in the LF:HF ratio and its SD suggest an increased sympathetic tone and discordance in sympathovagal activity in moderate OSA, which is blunted in severe OSA. CPAP may restore autonomic defects, characteristic of severe OSA, to moderate levels. [source] The effects of 12 months of growth hormone replacement therapy on cardiac autonomic tone in adults with growth hormone deficiencyCLINICAL ENDOCRINOLOGY, Issue 6 2005F. Tanriverdi Summary Objectives, Growth hormone deficiency (GHD) in adults is associated with a cluster of cardiovascular risk factors. Some abnormalities of cardiac structure and function have been reported in adult patients with GHD, but there are few data related to cardiac autonomic tone. Non-invasive assessment of cardiac autonomic status can be achieved by heart rate variability (HRV), which can be measured by using time-domain or frequency-domain variables. To our knowledge, short-term (6 months) effects of GH replacement therapy (GHRT) on HRV in a limited number of patients have been evaluated prospectively in only two previous studies. The present study was therefore designed to investigate the effects of GHD and 12 months of GHRT on cardiac autonomic tone in a larger number of adult patients with severe GHD. Patients and methods, HRV measurement, by using time-domain variables, was performed in 22 patients with GHD (eight men, 14 women; mean age 45·4 ± 2·4 years) and 22 healthy controls (nine men, 13 women; mean age 40·8 ± 1·8 years) at baseline. The time-domain variables (sympathetically influenced parameters SDNN and SDANN and parasympathetically influenced parameters RMSSD and PNN50) were derived from 24-h electrocardiogram (ECG) recordings. In the patient group, cardiac autonomic tone was re-evaluated after 6 and 12 months of GHRT. Results, Mean baseline values of SDNN and SDANN were significantly higher (higher values mean lower sympathetic activity) in GHD patients than in healthy controls (P < 0·05), but mean baseline values of RMSSD and PNN50 did not differ significantly in healthy controls and patients. After 6 and 12 months of GHRT, mean SDNN and SDANN were decreased significantly when compared with the baseline values before GHRT (P < 0·05). However, mean RMSSD and PNN50 did not differ significantly from baseline. When SDNN and SDANN measurements were evaluated individually for each patient, after 12 months of GHRT both of the sympathetically influenced parameters decreased in 90% of the patients. Conclusions, These data indicate that sympathetic tone is decreased in adult patients with severe GHD. Additionally, an increment in sympathetic activity and normalization of sympathovagal balance have been demonstrated after 6 and 12 months of GHRT. This result suggests that, at least at the doses used in this study, GHRT improves sympathetic tone, without an obvious arrhythmogenic effect. [source] | |||||||||||||||||||