Power Spectral Analysis Of Heart Rate Research Articles

Experimental uninephrectomy associates with less parasympathetic modulation of heart rate and facilitates sodium-dependent arterial hypertension.

Blood pressure is known to be increased in kidney donors following living-donor kidney transplantation. However, the physiological underpinnings of the blood-pressure increase following uninephrectomy remain unclear. We hypothesized that changes in sympathetic tone or in parasympathetic modulation of sinus node function are involved in the blood-pressure increase following experimental kidney-mass reduction. C57BL6N mice (6 to 11 per group) subjected to sham surgery (controls) or uninephrectomy with or without a one-week course of sodium chloride-enriched, taurine-deficient diet were studied. Uninephrectomized mice treated with a subcutaneous infusion of angiotensin-II over a period of one week were positive controls. A transfemoral aortic catheter with telemetry unit was implanted, readings of heart-rate and blood-pressure were recorded. Powerspectral analysis of heart rate and systolic blood pressure was performed to gain surrogate parameters of sympathetictone and parasympathetic modulation of sinus node function. Baroreflex sensitivity of heart rate was determined from awake, unrestrained mice using spontaneous baroreflex gain technique. Systolic arterial blood pressure, heart rate and baroreflex sensitivity were not different in uninephrectomized mice when compared to controls. Parasympathetic modulation of sinus node function was less in uninephrectomized mice in comparison to controls. Uninephrectomized mice of the high-angiotensin-II model or of the high-salt and taurine-deficiency model had an increased systolic arterial blood pressure. Uninephrectomy associated with less parasympathetic modulation of sinus node function. The combination of uninephrectomy, taurine-deficiency and high-salt intake led to arterial hypertension.

Response Analysis of Hemodynamics Parameters to Tyramine Infusion Post‐Exercise Training in Spountaneously Hypertensive Rats

The aim of the study was to assess the effects of exercise training in the vascular control after sympathetic stimulation mimicked by tyramine infusion in spontaneously hypertensive rats (SHR). Thirty two male SHR and wistar kyoto were submitted or not to a swimming protocol, resulting in four groups: sedentary normotensive (SN), trained normotensive (TN), sedentary hypertensive (SH) and trained hypertensive (TH). Arterial pressure (AP), heart rate (HR), power spectral analysis of HR (HRV), systolic AP variability (SAPV) and diastolic (DAPV) were recorded in baseline conditions. Following, the infusion of tyramine was administrated. Resting bradycardia was observed in both TN and TH rats compared with their respective sedentary animals. Exercise training attenuated AP in TH vs. SH. The variance of HRV was lower in SH vs. TH. The variance of SAPV and DAPV were higher in SH vs. TH. The LF component of HRV, SAPV and DAPV were lower in TH than SH. The pressor response to tyramine was enhanced in trained SHR but not kyoto. In conclusion, the results points to a sympatolitic effect of exercise training, probably at pre synaptic level, suggesting an up regulation of α<sub style=”text‐align: start;”>1‐receptors in vascular smooth muscle. These findings showed that exercise training may be a therapeutic tool for improving function in hypertensive individuals.

高血压患者长程心功率谱分析结果的重复性研究

objective: To investigate the repeatability of the result on 24 hour heart rate power spectral analysis Methods: 45 DCG data of high blood pressure patients were analyzed thrice by the same software of 24 hours heart rate power spectrum to compare the difference of the result between two technical personnel. Results: The result of the same DCG data analysis between two technicians were of no significant difference ( P > 0.05). The result of the same DCG data analysis by one of the two technicians one month later was still of no significant difference. ( P > 0.05). Conclusion: The repeatability of 24 hour heart rate power spectral analysis based on different factors plays an important role in scientific research and clinical practice.

Response analysis of hemodynamics parameters to tyramine infusion post‐physical training in spountaneously hypertensive rats (546.5)

The aim of the present study was to assess the effects of exercise training in the vascular control after sympathetic stimulation by tyramine infusion in spontaneously hypertensive rats (SHR). 33 male SHRs and WKY were submitted or not to a swimming protocol during 8 weeks, resulting in four groups: sedentary normotensive (SN, n=7), trained normotensive (TN, n=8), sedentary hypertensive (SH, n=8) and trained hypertensive (TH, n=10) rats. Arterial pressure (AP), heart rate (HR), means of power spectral analysis of HR (HRV), systolic AP variability (SAPV) and diastolic (DAPV) were recorded in baseline conditions. Following, the infusion of tyramine in three doses was administrated. Exercise training attenuated AP in TH vs. SH (p<0.001). The variance of HRV was lower in SH vs. TH (p=0.018). The other hand, the variance of SAPV and DAPV were higher in SH vs. TH (p=0.05). The LF component of HRV, SAPV and DAPV were lower in TH than SH (p<0.05). LF/HF was lower in TH than SH (p<0.05). The TN and TH presented an increased parasympathetic modulation compared with SN and SH (p<0.05). Pressor response to tyramine was enhanced in TH, but not in WKY. In conclusion, the results points to a sympatolitic effect of exercise training. This conclusion is supported by the impaired tyramine pressor response, suggesting an up regulation of α1‐receptors in vascular smooth muscle, once the administration of an agonist showed enhanced and the norepinephrine releaser showed impairment or the pressor response. These findings suggest that exercise training may be a therapeutic tool for improving function in hypertensive individuals.

Carotid body denervation prevents pulmonary edema, attenuates left ventricular remodeling and restores normal autonomic balance in chronic heart failure after myocardial infarction (709.5)

Background: The hypersensitive peripheral chemoreflex induces sympathoexcitation and vagolysis and is known to associate with the poor prognosis of chronic heart failure (CHF). We hypothesized that denervation of carotid body (CBD) improves CHF and restore the normal autonomic balance in a rat model of myocardial infarction (MI)‐induced CHF. Methods: We created MI‐induced CHF in rats. Surviving rats at 4 weeks after MI were randomized into CBD (n=10) and sham‐operated (Sham; n=10) group. To establish CBD, we removed the tissues around the carotid bifurcation. Two months after CBD, we evaluated physiological and histological findings. Results: CBD significantly reduced biventricular weight (2.9±0.1 vs. 3.3±0.1 g/kg, p<0.05), lung weight (5.6±0.4 vs. 8.1±0.3 g/kg, p<0.05), LV end‐diastolic pressure (13.7±3.2 vs. 28.3±3.1 mmHg, p<0.05) and heart rate (HR) (336±6 vs. 364±5 bpm, p<0.05). Power spectral analysis of HR demonstrated the increased power in the high frequency range (29.0±8.2 vs. 81.0±9.5 n.u., p<0.05) indicating the restoration of vagal tone. Histologocal analysis showed CBD decrease fibrosis and the invasion of macrophages in myocardium. Conclusion: CBD prevents pulmonary edema, attenuates LV remodeling and restores normal autonomic balance in CHF rats. CBD can be a novel neuro‐modulating therapy for CHF patients.

Sympathoactivation and rho-kinase-dependent baroreflex function in experimental renovascular hypertension with reduced kidney mass.

BackgroundDysregulation of the autonomic nervous system is frequent in subjects with cardiovascular disease. The contribution of different forms of renovascular hypertension and the mechanisms contributing to autonomic dysfunction in hypertension are incompletely understood. Here, murine models of renovascular hypertension with preserved (2-kidneys-1 clip, 2K1C) and reduced (1-kidney-1 clip, 1K1C) kidney mass were studied with regard to autonomic nervous system regulation (sympathetic tone: power-spectral analysis of systolic blood pressure; parasympathetic tone: power-spectral analysis of heart rate) and baroreflex sensitivity of heart rate by spontaneous, concomitant changes of systolic blood pressure and pulse interval. Involvement of the renin-angiotensin system and the rho-kinase pathway were determined by application of inhibitors.ResultsC57BL6N mice (6 to 11) with reduced kidney mass (1K1C) or with preserved kidney mass (2K1C) developed a similar degree of hypertension. In comparison to control mice, both models presented with a significantly increased sympathetic tone and lower baroreflex sensitivity of heart rate. However, only 2K1C animals had a lower parasympathetic tone, whereas urinary norepinephrine excretion was reduced in the 1K1C model. Rho kinase inhibition given to a subset of 1K1C and 2K1C animals improved baroreflex sensitivity of heart rate selectively in the 1K1C model. Rho kinase inhibition had no additional effects on autonomic nervous system in either model of renovascular hypertension and did not change the blood pressure. Blockade of AT1 receptors (in 2K1C animals) normalized the sympathetic tone, decreased resting heart rate, improved baroreflex sensitivity of heart rate and parasympathetic tone.ConclusionsRegardless of residual renal mass, blood pressure and sympathetic tone are increased, whereas baroreflex sensitivity is depressed in murine models of renovascular hypertension. Reduced norepinephrine excretion and/or degradation might contribute to sympathoactivation in renovascular hypertension with reduced renal mass (1K1C). Overall, the study helps to direct research to optimize medical therapy of hypertension.

The study on circadian rhythm of cardiac autonomic nervous activity and the intervention with enalapril in stage I to II essential hypertensives

Objectives: To study the circadian rhythm of cardiac autonomic nervous activity (ANA) in essential hypertension and observe the effect of treatment with enalapril on it. Methods: 24h heart rate power spectral analysis (HRPSA) and 3D HRPS graph were performed in 30 pre-and-post treatment patients with stage I to II essential hypertension (EH I–II). 153 patients with EH I–II, 40 patients with EH III and 30 healthy normotensives. Results: (1) In EH I–II group, TP, VLF, LF and HF were higher apparently (P<0.05) at late night (3–4 am) than those of normotensive group, whereas LF/HF had no difference (P>0.05) between two groups in every interval.

Effects of sevoflurane on QT parameters in children with congenital sensorineural hearing loss

Sevoflurane prolongs the QT interval (QTI). Patients with congenital sensorineural hearing loss (SNHL) often have a prolonged QTI. This study was to investigate the effects of sevoflurane on the QTI in SNHL and control children. Thirty patients with SNHL and 30 controls were studied. The corrected QT interval (QTc), interval from peak to end of T wave (Tp-e) and QT variability index (QTVI) were analysed. QTc and Tp-e were estimated by the average QTc and Tp-e measured beat-by-beat for 15 min. Heart rate power spectral analysis was performed. In both groups, QTc and QTVI increased during anaesthesia, but Tp-e did not change. There were no differences in QTc, QTVI, Tp-e, low- and high-frequency power between the two groups. In both groups, sevoflurane lengthened the QTc and QTVI intervals but not Tp-e.

Autonomic activity during dexmedetomidine or fentanyl infusion with desflurane anesthesia

Study Objective To evaluate autonomic activity with dexmedetomidine or fentanyl infusion and desflurane anesthesia during laparoscopic gastric banding. Study Design Randomized, single-blinded, open-label study. Setting Operating rooms at a university hospital. Subjects 40 patients scheduled for laparoscopic gastric banding with a mean body mass index of 50 kg/m 2. Interventions Patients received either dexmedetomidine (0.5 μg/kg given intravenously over 10 minutes, 0.4 μg · kg −1 · h −1, n = 20) or fentanyl (0.5 μg · kg −1 bolus, 1 μg · kg −1 · h −1, n = 20) during anesthesia. Response entropy of the electroencephalogram was maintained at 45 ± 5 by adjusting end-tidal desflurane concentration. Measurements In the operating room, blood pressure, heart rate (HR), response entropy, end-tidal desflurane concentration, tone entropy, and power-spectral analysis of HR were measured with the patient awake; 20, 40, and 60 minutes from intubation and the start of drug infusion; and at extubation. Main Results The mean end-tidal desflurane concentration during anesthesia was 4.0% ± 0.6% with dexmedetomidine and 4.1% ± 0.7% with fentanyl, indicating a similar anesthetic requirement in both groups. Autonomic activity, determined by tone entropy and spectral analysis of HR, decreased by 50% during anesthesia in both groups. The dexmedetomidine group showed a greater decrease in sympathovagal balance during anesthesia. Conclusion Both dexmedetomidine and fentanyl facilitated anesthesia and attenuated autonomic activity. Dexmedetomidine produced a greater decrease in sympathovagal balance than fentanyl.

Autonomic nervous system and microvascular alterations in normotensives with a family history of hypertension

Autonomic nervous system and microvascular alterations at pre‐hypertensive stage of hypertension have still not been fully elucidated. We aimed at addressing central and local influences on microvascular reactivity at pre‐hypertensive stage of hypertension. To that end, we studied microvascular reactivity in 59 normotensives with a family history of hypertension and 46 controls. We measured laser‐Doppler flow on the finger nailfold skin in the resting condition, after an 8‐min occlusion of digital arteries and during local nitroglycerin application. Finger pressure, pulse and ECG were monitored by a Finapres device. Heart rate power spectral analysis was performed using Fast Fourier transformation. Baroreflex sensitivity was estimated by the sequence method. Normotensives with a family history of hypertension showed higher systolic pressure, decreased high‐frequency power of the heart rate variability spectrum and reduced baroreflex sensitivity in the resting condition as well as decreased fundamental frequency of laser‐Doppler flow oscillations during nitroglycerin application. We conclude that normotensives with a family history of hypertension exhibit altered sympathovagal balance with decreased parasympathetic activity at the cardiac level as well as increased myogenic microvascular reactivity.

Effect of Angiotensin-Converting Enzyme Inhibition on Sympathetic Tone in Patients With Mild to Moderate Heart Failure.

Sixteen patients with mild to moderate heart failure were examined to investigate whether sympathetic deactivation plays a role in the improvement in the failing heart by chronic angiotensin converting enzyme (ACE) inhibition. Measurements, including echocardiography, blood examinations, neurohumoral samplings (atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), norepinephrine), and spectral heart rate variability analysis by Holter electrocardiography, were carried out before and 6 months after the administration of lisinopril (5-10 mg/day). Quality of life assessment was accomplished by the Specific Activity Scale (SAS) questionnaire. Treatment with lisinopril for 6 months resulted in a significant reduction in systolic blood pressure. The left ventricular diastolic dimension significantly decreased and fractional shortening significantly increased on echocardiography. Of the 16 patients, 8 had improvement in their symptoms as measured by the SAS. Lisinopril did not significantly reduce the plasma norepinephrine concentration, but there was a significant reduction in the plasma ANP and BNP concentrations. In the heart rate power spectral analysis, total spectral power, high-frequency components and low/high frequency ratios did not change significantly with lisinopril. The mechanism by which ACE inhibitors improve mild to moderate heart failure is not by suppressing sympathetic activity.

Cardiac responses to mild hypoxic hypercapnia in newborn babies: no effect of sleep position.

To evaluate whether cardiac responses to a level of hypoxic hypercapnia that may be observed in rebreathing studies are altered with infant sleep position. Eighteen healthy term infants (< 5-days-old) were studied. Heart rate (HR) and HR variability were monitored during air breathing and during 3 min exposure to a mixture of 15% O2/3% CO2 in both the prone and supine positions. Power spectral analysis of HR was performed. Heart rate was the only measured variable to be significantly changed in response to 15% O2/3% CO2. Hypoxic hypercapnia elicited no significant responses in power spectral HR variables. There was no effect of sleeping position on any of the measured variables. There are no significant differences in cardiac responses to mild hypoxic hypercapnia between sleep positions and power spectral indices of the autonomic control of HR are not altered by sleep position in newborn babies.

Heart rate, heart rate variability, and blood pressure during perioperative stressor events in abdominal surgery

To define the behavior of power spectral heart rate variability (PSHR) during potentially stressful events in the perioperative period, and relate it to changes in blood pressure (BP) and heart rate (HR). Longitudinal clinical study. Operating room and recovery suites of a large tertiary care referral center. 26 ASA physical status I, II, and III patients undergoing elective abdominal surgery. Anesthesia was induced with thiopental sodium and fentanyl, and maintained with isoflurane/nitrous oxide (N2O)/relaxant or enflurane/N2O/relaxant. The trachea was intubated and intraabdominal surgery was performed. Observations consisted of HR, noninvasive blood pressure, and PSHR. They were made before and after induction of anesthesia, tracheal intubation, and surgical incision, and during maximal surgical stimulation and skin closure. HR and mean arterial pressure (MAP) maxima were also recorded for one hour before and after emergence from anesthesia. PSHR was obtained using a special algorithm and data acquisition system for real time spectral analysis of the instantaneous HRversus time function. The HR power spectrum parameters analyzed were low-frequency (LFA; powerband = 0.04 to 0.10 Hz), respiratory-induced frequency (RFA; powerband = respiratory frequency +/- 0.06 Hz), and the ratio of LFA to RFA. With induction of anesthesia, only RFA power decreased significantly. LFA power reduction became significant only after intubation and continued so until after incision. Immediately after induction, the decline in RFA power (vs. preinduction) was more pronounced when compared with the decline in LFA power (76% vs. 34%; p = 0.01). Hence, the ratio LFA/RFA increased significantly after induction of anesthesia. It was significantly higher than at postintubation, preincision, or skin closure. A significant elevation in LFA, LFA/RFA ratio, and BP occurred with maximal abdominal surgical stimulation. Only preinduction LFA, RFA, and LFA/ RFA ratio were predictive of MAP changes with induction of anesthesia (p = 0.006). In 8 of the 15 patients who had MAP changes of at least 10 mmHg with induction, PSHR indices correctly predicted a change of this magnitude. Late intraoperative HR maxima were positively correlated with the change in HR and incision (r2 = 0.58; p < 0.01). The change in BP with incision was positively correlated with early postoperative HR maxima (r2 = 0.60; p < 0.01). On anesthetic induction, preoperative, but not intraoperative, spectral indices were predictive of BP changes. Power spectral analysis of HR may provide information about the autonomic state that is not evident from BP or HR. The HR power spectrum, in particular, indicated a striking autonomic imbalance immediately after the induction of anesthesia despite stable HR and BP. LFA and LFA/RFA ratio appeared to track sympathetic autonomic activation during abdominal surgical stimulation, but not during other perioperative stressor events.

Power spectral analysis of heart rate in hyperthyroidism.

The aim of the present study was to evaluate the impact of hyperthyroidism on the cardiovascular system by separately analyzing the sympathetic and parasympathetic influences on heart rate. Heart rate variability was evaluated by autoregressive power spectral analysis. This method allows a reliable quantification of the low frequency (LF) and high frequency (HF) components of the heart rate power spectral density; these are considered to be under mainly sympathetic and pure parasympathetic control, respectively. In 10 newly diagnosed untreated hyperthyroid patients with Graves' disease, we analyzed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. In addition, heart rate variations during deep breathing, lying and standing, and Valsalva's maneuver were analyzed. The results were compared to those obtained from 10 age-, sex-, and body mass index-matched control subjects. In 8 hyperthyroid patients, the same evaluation was repeated after the induction of stable euthyroidism by methimazole. Heart rate power spectral analysis showed a sharp reduction of HF components in hyperthyroid subjects compared to controls [lying, 13.3 +/- 4.1 vs. 32.0 +/- 5.6 normalized units (NU; P < 0.01); standing, 6.0 +/- 2.7 vs. 15.0 +/- 4.0 NU (P < 0.01); mean +/- SEM]. On the other hand components were comparable in the 2 groups (lying, 64.0 +/- 6.9 vs. 62.0 +/- 6.5 NU; standing, 77.0 +/- 6.5 vs. 78.0 +/- 5.4 NU). Hence, the LF/HF ratio, which is considered an index of sympathovagal balance, was increased in hyperthyroid subjects while both lying (11.3 +/- 4.5 vs. 3.5 +/- 1.1; P < 0.05) and standing (54.0 +/- 12.6 vs. 9.8 +/- 2.6; P < 0.02). This parameter was positively correlated with both T3 (r = 0.61; P < 0.05) and free T4 (r = 0.63; P < 0.05) serum levels. Among traditional cardiovascular autonomic tests, the reflex response of heart rate during lying to standing was significantly lower in hyperthyroid patients than in controls (1.12 +/- 0.03 vs. 1.31 +/- 0.04; P < 0.002). No statistically significant difference in reflex responses between the two groups was found in deep breathing or Valsalva's maneuver. In the 8 patients reexamined after methimazole treatment, we observed complete normalization of altered cardiovascular parameters, with slight predominance of the vagal component compared with controls. These results suggest that thyroid hormone excess may determine reduced parasympathetic activity and, thus, a relative hypersympathetic tone.

Autonomic control of heart rate after brain injury in children

To study sequential changes in heart rate, respiratory rate, blood pressure, heart rate power spectra, and plasma catecholamine concentrations in patients with acute brain injury and correlate these variables with the severity of neurologic dysfunction and patient outcome. Prospective, clinical study. Pediatric intensive care unit. Thirty-seven pediatric patients with acute brain injury caused by trauma, anoxia/ischemia, hemorrhage, or infection. None. We found significant associations between low-frequency (0.01 to 0.15 Hz) heart rate power and severity of neurologic dysfunction (as assessed by the admission Glasgow Coma Scale) (p < .001) and patient outcome (as assessed by the Glasgow Outcome Scale) (p = .05). The admission (p = .05) and maximum (p < .001) values for low-frequency heart rate power and the minimum value for high-frequency (0.15 to 0.50 Hz) heart rate power obtained during hospitalization (p = .001) predicted an increased likelihood of survival. Ten brain-dead patients had significantly decreased low-frequency heart rate power (p = .008) and plasma norepinephrine (p = .015), epinephrine (p = .03), and dopamine (p = .04) concentrations when compared with six non-brain-dead patients with a Glasgow Coma Scale score of 3. Our results imply that autonomic nervous system control of heart rate is disrupted in proportion to the degree of neurologic insult in children after acute brain injury. Thus, heart rate power spectral analysis and plasma catecholamine concentrations may prove to be useful adjuncts in determining severity of neurologic injury and prognosis for recovery in children suffering from brain injury. In addition, these techniques may aid in the determination of brain death.

Decreased heart rate variability in panic disorder patients: A study of power-spectral analysis of heart rate

We have previously found decreased standard deviations and mean consecutive differences of R-R intervals in panic disorder patients in standing posture, compared with control subjects. In the present study, we used spectral analysis of heart rate variability to examine autonomic function in 21 panic disorder patients and 21 normal control subjects. Patients had a significantly lower standard deviation of heart rate in supine as well as standing postures. Absolute low frequency power (0.01-0.05 Hz) was also significantly lower in panic disorder patients in standing postures. Upon standing, the panic disorder patients had significantly higher relative mid-frequency power (0.07-0.15 Hz). During a standing deep-breathing condition at six breaths per minute, the patients had a significantly decreased absolute and relative mid-frequency (0.07-0.15 Hz) power compared with control subjects. These findings suggest a decrease in cholinergic and a relative increase in adrenergic responsiveness in panic disorder patients compared with control subjects.

Spectral Analysis of Heart Rate in Diabetic Autonomic Neuropathy

Power spectral analysis of the heart rate was compared with standard tests of autonomic function performed on 15 insulin-dependent diabetic patients with symptoms of autonomic dysfunction. The high-frequency power, low-frequency power, and total power of the heart rate power spectrum measured in the supine position--possible measures of parasympathetic nervous system function--were significant predictors of the expiratory-inspiratory ratio, the beat-to-beat heart rate difference on deep respiration, the standard deviation of the resting heart rate, the 30:15 ratio, and the Valsalva ratio. The change in low-frequency power on moving from the supine to upright position, a possible measure of sympathetic nervous system function, was a modest predictor of the systolic and diastolic blood pressure fall in response to postural change, but a poor predictor of the blood pressure response to isometric exercise and a cold stimulus. This study supports the role of heart rate power spectral analysis as a clinical test of autonomic function in patients with known or suspected autonomic failure.