Differences Of Successive NN Intervals Research Articles

Changes in Cardiac Autonomic Activity During a Passive 8 Hour Acute Exposure to 5 500 m Normobaric Hypoxia are not Related to the Development of Acute Mountain Sickness

Alterations in the autonomic nervous system after ascent to high altitude may be related to the development of acute mountain sickness (AMS). So far, the time course of cardiac autonomic modulation in relation to AMS development during the early hours at altitude is not well established. As AMS develops sometimes as early as 1 h and typically within 6 to 10 h at altitude, evaluating this time period provides information on cardiac autonomic responses with regard to AMS development. Prior studies exclusively investigated autonomic modulations in hypobaric hypoxia. Because barometric pressure per se might influence autonomic nervous system activity, the evaluation of cardiac autonomic alterations caused by hypoxia alone might give new insights on the role of the autonomic nervous system in AMS development. To assess the early responses of acute hypoxia on cardiac autonomic modulation and its association to the development of AMS, 48 male subjects were exposed for 8 h to acute normobaric hypoxia (FiO2 11.0%, 5 500 m respectively). Heart rate variability (HRV) was determined by 5-min recordings of successive NN-intervals in normoxia and after 2, 4, 6 and 8 h in hypoxia. Compared with normoxia, acute exposure to hypoxia decreased total power (TP), high frequency (HF) and low frequency (LF) components as well as the standard deviation of all NN intervals (SDNN), the root mean square of differences of successive NN intervals (rMSSD) and the proportion of differences between adjacent NN intervals of more than 50 ms (pNN50). LF:HF ratio, heart rate (HR) and blood lactate (LA) were augmented, indicating an increase in cardiac sympathetic activity. No differences were found between those who developed AMS and those who did not. Our results confirm reduced HRV with a shift towards sympathetic predominance during acute exposure to hypoxia. However, changes in cardiac autonomic modulations are not related to AMS development in acute normobaric hypoxia.

The Influence of Subclinical Hyperthyroidism on Blood Pressure, Heart Rate Variability, and Prevalence of Arrhythmias

The impact of subclinical hyperthyroidism (sHT) on the cardiovascular system still needs to be elucidated. The aim of the study was to prospectively assess blood pressure (BP), variability in heart rate, and the prevalence of arrhythmias in patients with sHT, both before and after they are restored to the euthyroid state.The study group consisted of 44 normotensive patients (37 women, 7 men), aged 22-65 years (mean±SD: 45.9±11.0) with sHT. Enrolled patients were drawn from 1080 patients referred to our department for treatment of hyperthyroidism. Study patients were treated with radioiodine treatment to restore the euthyroid state. Ambulatory BP monitoring and Holter electrocardiography were performed (i) when sHT was diagnosed and (ii) at least 6 months after they became euthyroid.sHT in comparison to the euthyroid state was associated with higher (109.3±7.1 vs. 107.1±7.7 mmHg) nocturnal systolic mean BP (p=0.035) and BP load (14.8 vs. 10.2%, p=0.033), mean diastolic BP (66.4±6.6 vs. 64.8±6.6 mmHg, p=0.047), and mean arterial pressure (80.8±43.1 vs. 79.3±43.6 mmHg, p=0.049). Moreover, significant changes in both the time and frequency domain measures of heart rate variability (HRV) were observed: decrease of the square root of the mean squared differences of successive NN intervals (rMSSD) (45.68±34.1 vs. 65.09±50.6 ms, p=0.03) and the low frequency power (LF) (5.71±0.99 vs. 6.0±1.01 ms(2), p=0.049) as well as increase of QT interval dispersion (58.25±28.5 vs. 46.90±12.1 ms, p=0.020). This was accompanied by a clinically insignificant increase in the frequency of ventricular extrasystoles (VES) (3.1±7.4 vs. 0.6±1.2 per hour, p=0.048) and increased mean heart rate (78.4±6.8 vs. 76.0±8.0 beats/min, p=0.004). Some of the parameters correlated positively with thyroid hormones: nocturnal diastolic BP with free triiodothyronine (FT(3)) (r=0.397, p=0.008), rMSSD with free thyroxine (FT(4)) (r=0.389, p=0.013), and QT interval dispersion with FT(4) (r=0.450, p=0.004).The study suggests that sHT in comparison to euthyroid status may be associated with a statistically significant but probably clinically insignificant increase of QT interval dispersion, prevalence of VES, elevated nocturnal arterial BP, and changes in HRV. These findings broaden our understanding of the cardiovascular effects of sHT.

Heart rate variability in patients with vascular dementia

Objective To determine the roles of heart rate variability(HRV) in evaluating cardiac autonomic nerve function of patients with vascular dementia.Methods Totally 124 patients with vascular dementia and 102 control subjects received 24h dynamic Holter monitoring to perform frequency domain measures,time domain measures and non-linear analysis of HRV. The following HRV spectral parameters were considered:total frequency power(TF),low frequency power(LF),high frequency power(HF),standard diviation of normal-to-normal intervals(SDNN),square-root of mean squared differences of successive NN intervals(RMSS),and standard deviation of SDNN(SDSD).Poincare plot descriptors included vector angle index(VAI) and vector length index(VLI).Results The time domain measures(SDNN,RMSS,SDSD),frequency domain measures(TF,LF,HF),VAI and VLI were significantly lower in patients with vascular dementia than in control subjects[SDNN:(78±28) vs(129±30)ms,RMSS: (20±8) vs(24±8)ms,SDSD:(17±7) vs(22±8)ms,P0.01;TF:(1432±621) vs(1962±583) ms~2/Hz,LF:(934±347) vs (1309±371)ms~2/Hz,HF:(473±174) vs(601±247)ms~2/Hz,P0.01;VAI:(0.54±0.14) vs(0.67±0.13)ms,VLI:(154±19) vs(194±25)ms,P0.01].There were less patients who had Poincare scatter grams in shape of comet in patients with vascular dementia than in control subjects.Conclusion We recommend to perform HRV analysis,a noninvasive mehtod,for patients with vascular dementia to evaluate the cardiac autonomic nerve function.

Immediate Effects of Reiki on Heart Rate Variability, Cortisol Levels, and Body Temperature in Health Care Professionals With Burnout

Burnout is a work-related mental health impairment comprising three dimensions: emotional exhaustion, depersonalization, and reduced personal accomplishment. Reiki aims to help replenish and rebalance the body's energetic system, thus stimulating the healing process. The objective of this placebo-controlled, repeated measures, crossover, single-blind, randomized trial was to analyze the immediate effects of Reiki on heart rate variability (HRV), body temperature, and salivary flow rate and cortisol level in health care professionals with burnout syndrome (BS). Participants included 21 health care professionals with BS, who were asked to complete two visits to the laboratory with a 1-week interval between sessions. They were randomly assigned the order in which they would receive a Reiki session applied by an experienced therapist and a placebo treatment applied by a therapist with no knowledge of Reiki, who mimicked the Reiki treatment. Temperature, Holter ECG recordings (standard deviation of the normal-to-normal interval [SDNN], square root of mean squared differences of successive NN intervals [RMSSD], HRV index, low frequency component [LF], and high frequency component [HF]), salivary flow rate and cortisol levels were measured at baseline and postintervention by an assessor blinded to allocation group. SDNN and body temperature were significantly higher after the Reiki treatment than after the placebo. LF was significantly lower after the Reiki treatment. The decrease in the LF domain was associated with the increase in body temperature. These results suggest that Reiki has an effect on the parasympathetic nervous system when applied to health care professionals with BS.

Decreased Heart Rate Variability in HIV Positive Patients Receiving Antiretroviral Therapy: Importance of Blood Glucose and Cholesterol

The presence of autonomic dysfunction in HIV patients is largely unknown. Early studies found autonomic dysfunction in patients with AIDS. Antiretroviral combination therapy (ART) has dramatically changed the course of the disease and improved prognosis and decreased morbidity.AimTo evaluate whether autonomic dysfunction is present in an ART treated HIV population and if so to identify factors of importance.MethodsHIV patients receiving ART for at least 12 months (n = 97) and an age-matched control group of healthy volunteers (n = 52) were included. All were non-diabetic and had never received medication for hypertension. Following a 10 min resting period a 15 min ECG recording was performed. Heart-rate variability (HRV) analysis was performed in accordance with current guidelines and data reported as mean [interquartile range].ResultsMean normal-to-normal (NN) and total HRV measured as standard deviation of normal-to-normal (SDNN) was lower in HIV patients compared to controls (905 vs. 982 ms; p<0.001 and 48 vs. 54 ms; p = 0.028, respectively). No differences were found between the groups in parasympathetic activity measured as square root of the mean squared difference of successive NN-intervals (RMSSD) or the percent of differences between adjacent NN intervals greater than 50 ms (pNN50). In the HIV positives, haemoglobin A1c correlated inversely with SDNN, RMSSD and pNN50 (p<0.05). Total cholesterol and LDL-C correlated inversely with RMSSD and pNN50 (p<0.05). Neither HIV duration, HIV-RNA, CD4 cell count nor CD4 nadir correlated with time or phase domain HRV variables.ConclusionsModerate autonomic dysfunction is present in HIV positives patients even with suppressed viral load due to ART. The dysfunction is correlated with HbA1c and hypercholesterolemia but not to duration of HIV or whether the patients were receiving protease inhibitors as part of the ART regime.

Increased Total Heart Rate Variability and Enhanced Cardiac Vagal Autonomic Activity in Healthy Humans with Sinus Bradycardia

Sinus bradycardia can be defined as a sinus rhythm with a resting heart rate of 60 beats per minute or less. While it is assumed that increased autonomic parasympathetic activity is associated with sinus bradycardia, such an association has yet to be proven. The aims of this study were to compute a number of heart rate variability (HRV) parameters in healthy individuals with sinus bradycardia and determine whether there was a significant vagal component to sinus bradycardia. Forty-three healthy adults with normal sinus rhythm and 25 healthy adults with sinus bradycardia had an electrocardiogram recorded for 20 minutes, from which HRV indices were calculated. Results showed significant increases in SDNN (standard deviation of NN intervals) (P< 0.05), RMSDD (square root of the mean squared differences of successive NN intervals) (P< 0.05), and DFA32 (detrended fluctuation analysis) (P< 0.05) in bradycardic subjects compared with subjects with normal sinus rhythm. There were no significant differences in sympathetic frequency domain indices between the two groups. In conclusion, there were significant increases in total heart variability and increased parasympathetic drive in subjects with bradycardia. Clinically, bradycardia is likely to be cardioprotective in aging populations based upon these HRV findings.

Short-Term Effects of Manual Therapy on Heart Rate Variability, Mood State, and Pressure Pain Sensitivity in Patients With Chronic Tension-Type Headache: A Pilot Study

Objective The purpose of this study was to investigate the immediate effects of head-neck massage on heart rate variability (HRV), mood states, and pressure pain thresholds (PPTs) in patients with chronic tension-type headache (CTTH). Methods Eleven patients (8 females), between 20 and 68 years old, with CTTH participated in this crossover study. Patients received either the experimental treatment (massage protocol) or a placebo intervention (detuned ultrasound). Holter electrocardiogram recordings (standard deviation of the normal-to-normal interval, square root of mean squared differences of successive NN intervals, index HRV, low-frequency component, and high-frequency component), PPT over both temporalis muscles, and Profile of Mood States questionnaire (tension-anxiety, depression-dejection, anger-hostility, vigor, fatigue, confusion) were obtained preintervention, immediately after intervention, and 24 hours postintervention. Self-reported head pain was also collected preintervention and 24 hours postintervention. Separate analyses of covariance (ANCOVAs) were performed with each dependent variable. The hypothesis of interest was group × time interaction. Results The ANCOVA showed a significant group × time interaction for index HRV (F = 4.5, P = .04), but not for standard deviation of the normal-to-normal interval (F = 1.1, P = .3), square root of mean squared differences of successive NN intervals (F = 0.9, P = .3), low-frequency component (F = 0.03, P = .8), or high-frequency component (F = 0.4, P = .5) domains. Pairwise comparisons found that after the manual therapy intervention, patients showed an increase in the index HRV ( P = .01) domain, whereas no changes were found after the placebo intervention ( P = .7). The ANCOVA also found a significant group × time interaction for tension-anxiety (F = 5.3, P = .03) and anger-hostility (F = 4.6, P = .04) subscales. Pairwise comparisons found that after the manual therapy intervention, patients showed a decrease in tension-anxiety ( P = .002) and anger-hostility ( P = .04) subscales, whereas no changes were found after the placebo intervention ( P > .5 both subscales). No significant changes were found in PPT levels (right F = 0.3, P = .6, left F = 0.4, P = .5). A significant group × time interaction for pain (F = 4.8, P = .04) was identified. No influence of sex was found (F = 1.5, P = .3). Pairwise comparisons showed that head pain (numerical pain rating scale) decreased 24 hours after manual therapy ( P < .05) but not after the placebo intervention ( P = .9). Conclusions The application of a single session of manual therapy program produces an immediate increase of index HRV and a decrease in tension, anger status, and perceived pain in patients with CTTH.

Effects of Functional Water on Heart Rate, Heart Rate Variability, and Salivary Immunoglobulin A in Healthy Humans: A Pilot Study

This study was designed to explore the effects of drinking an average dietary volume of functional water on blood pressure, short-term cardiovascular variables, and salivary immunoglobulin A. Subjects were studied in a randomized pre-post crossover design the morning after an overnight fast. Fifteen (15) healthy nonsmoking subjects, 8 males and 7 females, aged between 15 and 49 years, participated in the study. Short-term (10 minute) electrocardiography was measured in the participants before and after drinking either control mineral or functional water. The measurements were randomized, double blinded, and held two weeks apart. Saliva was collected for 4 minutes before the start of each electrocardiograph measurement. Blood pressure was monitored at 5 minute intervals for one hour as the mean of triplicate consecutive measurements. Drinking 100 mL of control mineral or functional water did not alter arterial blood pressure in the 60 minutes post-drinking. Drinking control mineral water led to a significant fall in the heart rate, although all time domain and power density parameters remained unaffected. Consumption of functional water resulted in a significant difference in all time domain measures and in three of the power density parameters. The heart rate fell, while RR interbeat intervals, standard deviation of the normal-to-normal heartbeats (SDNN), and the square root of the mean squared differences of successive NN intervals (RMSSD) increased. A large rise in low (LF) and high frequency (HF) power had a significant effect on total power, indicating homeodynamic balance. Elevated LF power indicated intensified spectral power at frequencies in the range of 0.1 Hz, thus improving autonomic stability. The effect on the heart rate may confirm changes in cellular metabolism. Parasympathetic pathway activation stimulated secretory immunoglobulin A on mucosal surfaces, which protects against pathogenic invasion. The drinking of functional water in healthy subjects elicited a rapid parasympathetic restorative response from the heart as well as stimulating mucosal humoral immunity. Functional water acts as an unconditional natural stimulus that elicits an involuntary response and facilitates physiological homeostasis.

Parasympathetic overactivity in patients with nasal septum deformities

Nasal septum deformities (NSD) are one of the most frequent reasons for nasal obstruction presented with a reduction in nasal airflow and chronic mucosal irritation. Nasocardiac reflex which includes afferent stimulus with maxillary division of the trigeminal nerve and the efferent pathway of the heart via the vagus nerve is not a well-known part of autonomic nervous system (ANS). Heart rate variability (HRV) is a parameter reflecting the ANS activity on heart. The purpose of this study is to evaluate ANS functions in patients with NSD by HRV analysis. Twenty-nine patients with NSD and 26 control subjects were included in the study. The diagnosis of NSD was made with history, symptoms, anterior rhinoscopy, and nasal endoscopic examination. 24-h ambulatory electrocardiographic recording was performed by a 3-channel recorder. HRV parameters were obtained by analyzing these parameters. Baseline features were similar in patients and controls (mean age: 31 ± 8 in the patients, 32 ± 9 in control subjects; P = NS). Night-RMSSD (the square root of square of mean square differences of successive NN intervals) (47 ± 21, 34 ± 13; P = 0.008), night-PNN50 (the number of interval differences of successive NN intervals greater than 50 ms) (24 ± 16, 14 ± 10; P = 0.007), 24-h-RMSSD (39 ± 18, 27 ± 12; P = 0.004), and 24-h-PNN50 (16 ± 12, 9 ± 7; P = 0.016) were significantly higher in patients than controls. Other HRV parameters were not significantly different between two groups. Changes in these parameters demonstrated an increased parasympathetic tone and discordance in sympatho-vagal activity in NSD.

Personal Coronary Risk Profiles Modify Autonomic Nervous System Responses to Air Pollution

We investigated whether PM2.5-mediated autonomic modulation depends on individual coronary risk profiles. Five-minute average heart rate (HR) and heart rate variability (HRV, including standard deviation of normal-to-normal intervals [SDNN], square root of the mean squared differences of successive NN intervals [rMSSD], high frequency [HF]) were measured from 24-hour ambulatory electrocardiograms, and personal PM(2.5) exposures were monitored in a prospective study of 10 male boilermakers (aged 34.3 +/- 8.1 years). We used the Framingham score to classify individuals into low (score = 1-3) and high (score = 5-6) risk categories. Mixed-effect models were used for statistical analyses. Each 1-mg/m(3) increase in the preceding 4-hour moving average PM(2.5) was associated with HR increase (5.3 beats/min) and HRV reduction (11.7%, confidence interval [CI] = 6.2-17.1% for SDNN; 11.1%, CI = 3.1-19.1% for rMSSD; 16.6%, CI = 1.5-31.7% for HF). Greater responses (2- to 4-fold differences) were observed in high-risk subjects than in low-risk subjects. Our study suggests that adverse autonomic responses to metal particulate are aggravated in workers with higher coronary risk profiles.

Heart Rate Variability and Obesity Indices: Emphasis on the Response to Noise and Standing

Obese people have a higher prevalence of cardiovascular disease, but the mechanism of this result remains obscure. The purpose of this study was to prove heart rate variability (HRV) response at rest and during stimuli in these persons. The subjects were 41 healthy persons (19 men, 22 women) ranging in age from 20 to 65 years. HRV was measured at rest and at given stresses with noise and standing. Higher levels of fat mass, percentage fat content, and waist/hip ratio were significantly associated with lower low frequency (LF) (r = -0.34, r = -0.43; P < .01, r = -0.33, P < .05), and lower root mean square differences of successive NN intervals (RMS standard deviation) (r = -0.33, r = -0.35, r = -0.38, P < .05). During rest, noise, and standing, the change amount of the standard deviation of NN interval (SDNN) and low frequency/high frequency ratio were not different between normal and obese groups (P > .05). Although there was no significant HRV response to stimuli, root mean square of successive differences (which reflects parasympathetic acivity) and low frequency (which mainly reflects sympathetic activity) were negatively correlated with fat mass, fat percentage, and waist-to-hip ratio at rest in obese persons. These results mean obesity can change cardiac autonomic nervous response, meaning that the mechanism by which obesity increases cardiac mortality would be explained, at least partially.

An approach to measure atrial and ventricular heart rate variability using pacemaker-mediated intracardiac electrograms.

Heart rate variability (HRV) measurements are usually performed from ventricular beat-to-beat intervals because of the difficulty to precisely locate the P wave fiducial point in surface ECG recordings. The aim of the study was to describe an approach to determine the atrial and ventricular HRV using pacemaker-mediated intracardiac electrograms. Twelve patients with the dual chamber pacemaker Logos were included. The atrial and ventricular intracardiac electrograms were transmitted with the high resolution telemetry channel of the pacemaker to an external recorder for 20 minutes while the patients were supine. During the measurements the patients were in sinus rhythm with intrinsic AV conduction. After computer assisted triggering of the atrial and ventricular events, the resultant intervals were used to calculate the standard deviation of all NN intervals (SDNN), the square root of the mean squared differences of successive NN intervals (RMSSD), and the percentage of successive interval differences >50 ms (pNN50). The differences between atrial and ventricular HRV-Indexes were assessed for each patient with a cut-off point of 1%. Differences >1% were analyzed in detail. A total of 15,504 heart cycles were analyzed. A manual correction due to false or not triggered atrial or ventricular events was necessary in 0.9%. The overall difference between atrial and ventricular pNN50 was-0.5%+/-2.1%and differences >1% were observed in 4 patients. The NN50 events occurred in the atrial as well as in the related ventricular interval in 84%. NN50 events occurred only in the atrium in 6% and only in the ventricle in 10%. The mean differences between atrial and ventricular SDNN and RMSSD were 0.4+/-2.1 ms and-0.1+/-3.5 ms with intra-individual differences <1%. The present study described a new method and demonstrated its feasibility to determine atrial as well as ventricular HRV from pacemakermediated intracardiac electrograms. The differences for pNN50 indicate that ventricular HRV did not reflect the changes of sinus node activity in all patients.

Assessment of Autonomic Nervous System by the Analysis of Heart Rate Variability in Patients with Variant Angina

Background and Objectives:Autonomic nervous discharge had been implicated in the pathogenesis of coronary artery spasm although the precise mechanisms by which coronary spasm is triggered remain to be elucidated. The purpose of this study was to assess the pattern of the autonomic nervous system in patients with variant angina through the analysis of heart rate variability. Materials and Methods:We compared the pattern of cardiac sympathetic and parasympathetic activity through the time domain and frequency domain analysis of heart rate variability with 24-hour Holter monitoring between 14 patients with variant angina and 14 healthy control subjects. None of the patients had organic coronary artery stenosis as determined by angiography Results:1 Among the time domain indices, the percent of successive normal NN intervals difference greater than 50 msec (pNN50 and the square root of the mean squared differences of successive NN intervals (rMSSD in the patient group were significantly lower than those in the normal control (p<0.05, repectively. 2 In the patient group, mean R-R intervals were significantly shortened from night to early morning compared to control group (p<0.05. 3 With frequency domian analysis, low frequency (0.04 to 0.15Hz spectrum, which is correlated with sympathetic activity, was revealed no significant difference between two groups. From night to early morning, significant increase of high frequency (0.15 to 0.4 Hz spectrum, which is specific index for vagal activity, and significant decrease of the ratio of low to high frequency, which represents sympatho-vagal interaction, was blunted in the patient group (p<0.05. Conclusions:In variant angina, cardiac vagal influence on the heart rate was blunted and sympathetic activity was predominant at night and in the early morning. (Korean Circulation J 1999;29(6 :590-595