Showing papers on "Heart rate variability published in 1998"
TL;DR: The ATRAMI study as discussed by the authors provides clinical evidence that after myocardial infarction the analysis of vagal reflexes has significant prognostic value independently of LVEF and ventricular arrhythmias and that it significantly adds to the prognosis value of heartrate variability.
2,950 citations
TL;DR: CHF is associated with autonomic dysfunction, which can be quantified by measuring HRV, and a reduction in SDNN identifies patients at high risk of death and is a better predictor of death due to progressive heart failure than other conventional clinical measurements.
Abstract: Background—Patients with chronic heart failure (CHF) have a continuing high mortality. Autonomic dysfunction may play an important role in the pathophysiology of cardiac death in CHF. UK-HEART exam...
1,203 citations
TL;DR: Using the SDNN index, rMSSD and pNN50, HRV of healthy subjects, particularly those >65 years old, may decrease to below levels associated with increased risk of mortality, with measure-dependent patterns.
972 citations
TL;DR: A body of research has emerged that implicates a relative reduction in HRV and cardiac vagal tone in PD, as indicated by various HRV measures, and this contradiction is addressed in the context of traditional homeostatic models versus a systems perspective that views physiologic variability as essential to overall stability.
605 citations
TL;DR: Among normotensive men, lower HRV was associated with greater risk for developing hypertension, consistent with the hypothesis that autonomic dysregulation is present in the early stage of hypertension.
Abstract: Heart rate variability (HRV) is a useful noninvasive tool to assess cardiac autonomic function. The purpose of this study was to (1) compare measures of HRV between hypertensive and normotensive subjects and (2) examine the role of HRV as a predictor of new-onset hypertension. The first 2 hours of ambulatory ECG recordings obtained from 931 men and 1111 women attending a routine examination at the Framingham Heart Study were processed for HRV. Three time-domain and 5 frequency-domain variables were studied: standard deviation of normal RR intervals (SDNN), percentage of differences between adjacent normal RR intervals exceeding 50 milliseconds, square root of the mean of squared differences between adjacent normal RR intervals, total power (0.01 to 0.40 Hz), high frequency power (HF, 0.15 to 0.40 Hz), low frequency power (LF, 0.04 to 0.15 Hz), very low frequency power (0.01 to 0.04 Hz), and LF/HF ratio. On cross-sectional analysis, HRV was significantly lower in hypertensive men and women. Among 633 men and 801 women who were normotensive at baseline (systolic blood pressure <140 mm Hg and diastolic blood pressure <90 mm Hg and not receiving antihypertensive treatment), 119 men and 125 women were newly hypertensive at follow-up 4 years later. After adjustment for factors associated with hypertension, multiple logistic regression analysis revealed that LF was associated with incident hypertension in men (odds ratio per SD decrement [OR], 1.38; 95% confidence interval [CI], 1.04 to 1.83) but not in women (OR, 1.12; 95% CI, 0.86 to 1.46). SDNN, HF, and LF/HF were not associated with hypertension in either sex. HRV is reduced in men and women with systemic hypertension. Among normotensive men, lower HRV was associated with greater risk for developing hypertension. These findings are consistent with the hypothesis that autonomic dysregulation is present in the early stage of hypertension.
552 citations
TL;DR: Recent studies indicate that heart rate variability might soon become a similarly powerful tool for risk prediction and monitoring of disease progression in congestive heart failure and for monitoring or reinnervation after heart transplantation.
Abstract: Heart rate variability is a recognized tool for the estimation of cardiac autonomic modulations. Recently, several studies have advanced the field of heart rate variability in three areas: 1) in technical modes of electrocardiogram processing and heart rate variability assessment, 2) in physiologic understanding and interpretation, and 3) in clinical and practical use. The most recent technical studies concentrate on the analysis of nonlinear aspects of heart period variations and on coherence between electrocardiogram variability and other physiologic factors such as respiration. Principal physiologic investigations studied the components of heart rate variability attributable to the individual limbs of the autonomic nervous system. It is becoming recognized that behavior and responses to the environment, including the psychosocial environment, play an important role in long-term heart rate variability. Established clinical applications of heart rate variability are presently restricted to the assessment of risk after myocardial infarction and to the early diagnosis of diabetic neuropathy. Nevertheless, recent studies indicate that heart rate variability might soon become a similarly powerful tool for risk prediction and monitoring of disease progression in congestive heart failure and for monitoring or reinnervation after heart transplantation.
431 citations
TL;DR: Paroxetine and nortriptyline are effective treatments for depressed patients with ischemic heart disease and are associated with a significantly higher rate of serious adverse cardiac events compared with paroxetines.
Abstract: Main Outcome Measures.— For effectiveness of treatment, a decline in the score of the Hamilton Rating Scale for Depression by 50% and final score of 8 or less; for cardiovascular safety, heart rate and rhythm, supine and standing systolic and diastolic blood pressures, electrocardiogram conduction intervals, indexes of heart rate variability, and rate of adverse events. Results.— By intent-to-treat analysis, 25 (61%) of 41 patients improved during treatment with paroxetine and 22 (55%) of 40 improved with nortriptyline. Neither drug significantly affected blood pressure or conduction intervals. Paroxetine had no sustained effects on heart rate or rhythm or indexes of heart rate variability, whereas patients treated with nortriptyline had a sustained 11% increase in heart rate from a mean of 75 to 83 beats per minute (P,.001) and a reduction in heart rate variability, as measured by the SD of all normal R-R intervals over a 24-hour period, from 112 to 96 (P,.01). Adverse cardiac events occurred in 1 (2%) of 41 patients treated with paroxetine and 7 (18%) of 40 patients treated with nortriptyline (P,.03). Conclusions.— Paroxetine and nortriptyline are effective treatments for depressed patients with ischemic heart disease. Nortriptyline treatment was associated with a significantly higher rate of serious adverse cardiac events compared with paroxetine.
416 citations
TL;DR: Chronic insomniacs could be at increased risk for the development of disorders, such as coronary artery disease, that are related to increased sympathetic nervous system activity.
Abstract: Objective It was hypothesized that psychophysiological insomniacs, who have been shown to have elevated heart rate, body temperature, and whole body metabolic rate, would also have increased low frequency and decreased high frequency power in the spectral analysis of their heart period data. Method Groups of 12 objectively defined insomniacs and age-, sex-, and weight-matched controls with normal sleep were evaluated on sleep and EKG measures over a 36-hour sleep laboratory stay. Results Heart period was decreased (ie, heart rate was increased) and its SD was decreased in all stages of sleep in the insomniacs compared with the controls. Spectral analysis revealed significantly increased low frequency power and decreased high frequency power in insomniacs compared with controls across all stages of sleep. Conclusions Because increased low frequency spectral power is an indicator of increased sympathetic nervous system activity, these data imply that chronic insomniacs could be at increased risk for the development of disorders, such as coronary artery disease, that are related to increased sympathetic nervous system activity.
415 citations
TL;DR: The data show that physiological measures aresensitive to mental effort, whereas rating scales are sensitive to both mental effort and task difficulty.
Abstract: The sensitivity of physiological measures to mental workload has been investigated in a flight simulator. Twelve pilots had to fly through a tunnel with different levels of difficulty. Additionally, they had to perform a memory task with four levels of difficulty. The easiest memory task was combined with the easiest tunnel task and the most difficult memory task with the most difficult tunnel task. Between the tunnel tasks, subjects had to fly a pursuit task in which a target jet had to be followed. Rest periods before and after the experiment were used as a baseline for the physiolog-ical measures. Mental workload was measured with heart period, continuous blood pressure, respiration and eye blinks. Heart rate variability, blood pressure variability and the gain between systolic blood pressure and heart period (modulus) was derived from the measures. All measures showed differences between rest and flight, and between the pursuit and the tunnel task. Only heart period was sensitive to the different levels in the tunnel task. Since heart rate variability was affected by respiration, it could only be interpreted together with the respiratory data. The modulus, how-ever, was hardly influenced by respiration and therefore, appears te be a better measure than heart rate variability. From the respiratory parameters, the duration of a respiratory cycle was the most sensitive to changes in workload. The time in between two successive eye blinks (blink interval) increased and the blink duration decreased as more visual information had to be processed. Increas-ing the difficulty of the memory task leaded to a decrement in blink interval, probably caused by subvocal activity during the rehearsal of the letters. Blink duration was not influenced by memory load.
413 citations
TL;DR: It is indicated that I(KACh) is necessary for the fast fluctuations in heart rate responsible for beat-to-beat control of heart activity, both at rest and after vagal stimulation, which is critical for effective heart rate regulation in mice.
378 citations
TL;DR: Determination of QTD from the surface ECG even when performed with the best available methodology failed to predict subsequent risk in this large series of infarct survivors.
Abstract: Background —Risk stratification by means of analysis of QT dispersion (QTD) in the 12-lead surface ECG is under intense investigation in various patient populations. The aim of the present prospective study was to evaluate the prognostic value of QTD and other ECG variables reflecting dispersion of ventricular repolarization in comparison with established risk stratifiers during long-term follow-up in a large cohort of post–myocardial infarction patients treated according to contemporary therapeutic guidelines.
Methods and Results —In 280 consecutive infarct survivors, the 12-lead ECG was optically scanned and digitized for analysis of QTD (QTmax−QTmin) and 25 other repolarization variables, including recently developed and validated parameters such as the T peak–to–T end interval and the area under the T wave. In addition, a variety of established risk stratifiers were assessed. After a mean follow-up period of 32±10 months, 30 patients reached one of the prospectively defined study end points (death, ventricular tachycardia, or resuscitated ventricular fibrillation). Comparisons between event and nonevent patients by means of Kaplan-Meier event probability analyses revealed that none of the ECG dispersion variables were of discriminative value. In contrast, variables such as left ventricular ejection fraction ( P =0.007), mean 24-hour heart rate ( P =0.022), or heart rate variability ( P =0.007) proved to be potentially useful risk stratifiers in this patient population. On multivariate analysis, only LVEF, heart rate variability, and a history of thrombolysis were independent predictors of outcome.
Conclusions —Determination of QTD from the surface ECG even when performed with the best available methodology failed to predict subsequent risk in this large series of infarct survivors.
TL;DR: Cardiac autonomic modulation as determined by heart rate variability, is significantly lower in healthy women compared to healthy men, and this apparently paradoxical finding may be explained by lower sympathetic activity (low frequency power) in women.
Abstract: Aims Heart rate variability has been proposed as an indicator of cardiovascular health. Since women have a lower cardiovascular risk, we hypothesized that there are gender diVerences in autonomic modulation. Methods and Results In 276 healthy subjects (135 women, 141 men) between 18 and 71 years of age, 24 h heart rate and heart rate variability were determined. All heart rate variability parameters, except for pNN50 and high frequency power, were higher in men. After adjustment for heart rate, we obtained gender diVerences for: the standard deviation (P=0·049), the standard deviation of the 5 min average (P=0·047), low frequency power (absolute values, P=0·002; normalized units, P<0·001) and ratio low frequency/high frequency (P<0·001). There were no significant gender diVerences in heart rate variability parameters denoting vagal modulation. Gender diVerences were confined to age categories of less than 40 years of age. The majority of heart rate variability parameters decreased with age. Only in men, was a higher body mass index associated with a higher heart rate and with lower heart rate variability parameters (P<0·001). Conclusion Cardiac autonomic modulation as determined by heart rate variability, is significantly lower in healthy women compared to healthy men. We hypothesize that this apparently paradoxical finding may be explained by lower sympathetic activity (low frequency power) in women. This may provide protection against arrhythmias and against the development of coronary heart disease. (Eur Heart J 1998; 19: 1334‐1341)
TL;DR: Individuals with fibromyalgia have diminished 24-hour heart rate variability due to an increased nocturnal predominance of the low-frequency band oscillations consistent with an exaggerated sympathetic modulation of the sinus node.
Abstract: Objective To determine the accumulated 24-hour cardiovascular autonomic modulation and its circadian variations in patients with fibromyalgia, by means of heart rate variability analysis. Methods Thirty patients with fibromyalgia and 30 age- and sex-matched controls were studied prospectively. Assessments included a 24-hour ambulatory recording of heart rate variability, time-domain analysis of the accumulated 24-hour R-R interval variations, and power spectral analysis to determine the sympatho/ vagal balance at different hours (calculated as the power spectral density of the low-frequency [0.04-0.15-Hz] sympathetic band divided by the power of the high-frequency [0.15-0.50-Hz] parasympathetic band). Results Fibromyalgia patients had diminished accumulated 24-hour heart rate variability, manifested by a decreased standard deviation of all R-R intervals (mean +/- SD 126 +/- 35 ms, versus 150 +/- 33 ms in controls; P = 0.008) and a decreased ratio of pairs of adjacent R-R intervals differing by >50 ms (mean +/- SD 12.0 +/- 9.0% versus 20.1 +/- 18.0%; P = 0.031). Patients lost the circadian variations of sympatho/vagal balance, with nocturnal values significantly higher than those of controls at time 0 (mean +/- SD 3.5 +/- 3.2 versus 1.2 +/- 1.0; P = 0.027) and at 3 hours (3.3 +/- 3.0 versus 1.6 +/- 1.4; P = 0.01). Conclusion Individuals with fibromyalgia have diminished 24-hour heart rate variability due to an increased nocturnal predominance of the low-frequency band oscillations consistent with an exaggerated sympathetic modulation of the sinus node. This abnormal chronobiology could explain the sleep disturbances and fatigue that occur in this syndrome. Spectral analysis of heart rate variability may be a useful test to identify fibromyalgia patients who have dysautonomia.
TL;DR: Short recordings of HRV in a non-laboratory setting are stable over months and therefore characteristic of an individual and HRV derived from short recordings can be informative in population based studies.
Abstract: Objective To evaluate the stability of short recordings of heart rate variability (HRV) with time, and the association of HRV with age and sex. Design Five minute Holter recordings were made twice over a two month interval (tracking study). In addition, HRV was measured in a cross sectional study. Setting Residents of 11 Israeli kibbutzim were examined in their settlements. Subjects 32 men and 38 women (aged 31–67) participated in the tracking study and 294 (aged 35–65) were involved in the cross sectional study. Main outcome measures Time and frequency domain analyses on Holter recordings were undertaken in two breathing conditions: spontaneous and controlled breathing (15 respirations per minute). Regression was used to assess the relations of sex, age, heart rate, and logarithmically transformed HRV indices. Results HRV measures were highly consistent with time with correlations of 0.76–0.80 for high frequency and total power. Geometric mean total power declined with age by 45% in men and 32% in women, and was lower by 24% among women than among men (all p ⩽ 0.005). Men had a 34% higher very low and low frequency power and a higher ratio of low to high frequency power (p Conclusion Short recordings of HRV in a non-laboratory setting are stable over months and therefore characteristic of an individual. Strong age and sex effects were evident. HRV derived from short recordings can be informative in population based studies.
TL;DR: Altered long-term behavior of HR implies an increased risk of vascular causes of death rather than being a marker of any disease or frailty leading to death.
Abstract: Background—The prognostic role of heart rate (HR) variability analyzed from 24-hour ECG recordings in the general population is not well known. We studied whether analysis of 24-hour HR behavior is able to predict mortality in a random population of elderly subjects. Methods and Results—A random sample of 347 subjects of ≥65 years of age (mean, 73±6 years) underwent a comprehensive clinical evaluation, laboratory tests, and 24-hour ECG recordings and were subsequently followed up for 10 years. Various spectral and nonspectral measures of HR variability were analyzed from the baseline 24-hour ECG recordings. Risk factors for all-cause, cardiac, cerebrovascular, cancer, and other causes of death were assessed. By the end of 10-year follow-up, 184 subjects (53%) had died and 163 (47%) were still alive. Seventy-four subjects (21%) had died of cardiac disease, 37 of cancer (11%), 25 of cerebrovascular disease (7%), and 48 (14%) of various other causes. Among all analyzed variables, a steep slope of the power-l...
TL;DR: The ability of the QT variability index (QTVI), a measure of beat‐to‐beat QT interval fluctuations measured on a single ECG lead, to identify patients presenting with malignant ventricular arrhythmias and predict their subsequent occurrences was tested.
Abstract: QT Interval Variability and Sudden Death. Introduction: Recent studies have implicated repolarization lability in the genesis of malignant ventricular arrhythmias. However, few data exist on assessment of temporal QT interval variability and its relation to arrhythmogenesis. We tested the ability of the QT variability index (QTVI), a measure of beat-to-beat QT interval fluctuations measured on a single ECG lead, to identify patients presenting with malignant ventricular arrhythmias and predict their subsequent occurrences.
Methods and Results: We measured the QTVI in 95 patients presenting for electrophysiologic study (EPS). The ability of the QTVI to identify patients with sudden cardiac death (SCD) or sustained monomorphic ventricular tachycardia (MVT) on presentation and during follow-up of 23.7 ± 14.3 months was compared with spatial QT dispersion, T wave alternans ratio during atrial pacing, MVT inducibility at EPS, signal-averaged ECG, heart rate variability, and ejection fraction. The QTVI was higher in patients with heart disease than in controls (-0.7 ± 0.7 vs −1.1 ± 0.5, P < 0.05), and higher in patients presenting with SCD than in other patients with heart disease (0.0 ± 0.6 vs −0.8 ± 0.5, P < 0.05). The QTVI was the only clinical variable that identified patients who presented with SCD (P= 0.004, odds ratio = 12.5) on stepwise, logistic multiple regression. Fourteen patients had arrhythmic events during follow-up. In a Kaplan-Meier analysis of arrhythmic events, QTVI ≥ 0.1 was a discriminator for higher risk of arrhythmic events (P < 0.05).
Conclusions: (1) This noninvasive measure of temporal repolarization lability identified patients with SCD and predicted arrhythmia-free survival. (2) Further studies are needed to determine the mechanisms that mediate beat-to-beat QT interval variability.
TL;DR: In this article, the overnight profiles of cardiac interbeat autocorrelation coefficient of R-R intervals (r RR) calculated at 1-min intervals are related to the changes in sleep.
Abstract: We have recently demonstrated that the overnight profiles of cardiac interbeat autocorrelation coefficient of R-R intervals (r RR) calculated at 1-min intervals are related to the changes in sleep ...
TL;DR: Heritable factors may explain a substantial proportion of the variance in HR and HRV, and the contribution of genetic versus environmental factors to autonomic nervous system activity is highlighted.
Abstract: Background —There is evolving evidence that heart rate (HR) is genetically determined. Heart rate variability (HRV) measured by power spectral analysis provides quantitative phenotypic markers of autonomic nervous system activity. Reported determinants of HR and HRV only partially explain their variability in the population. The purpose of this study was to assess the heritability of HR and HRV and estimate the contribution of genetic factors to their variance.
Methods and Results —Subjects who underwent ambulatory recordings at a routine examination were eligible; subjects with congestive heart failure, coronary artery disease, diabetes mellitus, and those taking cardioactive medications were excluded. We analyzed high-frequency power, low-frequency power, very low-frequency power, total power, low-frequency/high-frequency ratio, and the standard deviation of normal R-R intervals from 2-hour continuous ECG recordings. Heritability analysis was done by studying correlations between siblings (n=682, in 291 sibships, 517 pairs) and between spouse pairs (n=206 pairs) after adjusting for important covariates. Results from separate models were combined to estimate the components of variance attributable to measured covariates, additive genetic effects (heritability), and household effects. After adjusting for covariates, the correlations were consistently higher among siblings (0.21 to 0.26) compared with spouses (0.01 to 0.19). The measured covariates in general accounted for 13% to 40% of the total phenotypic variance, whereas genetic factors accounted for 13% to 23% of the variation among HR and HRV measures.
Conclusions —Heritable factors may explain a substantial proportion of the variance in HR and HRV. These results highlight the contribution of genetic versus environmental factors to autonomic nervous system activity.
TL;DR: The initial results have shown that the variability of the PPG parameters shows promise for the assessment of the function of the autonomic nervous system.
Abstract: The heart rate variability is composed of low- and high-frequency fluctuations, which are mediated by the sympathetic and the parasympathetic nervous systems. The baseline and the amplitude of the photoplethysmographic (PPG) signal also show fluctuations in the same frequencies. In the current study, PPG examinations were performed on the fingers of normal subjects and diabetic patients, and three parameters were derived from each PPG pulse: the baseline of the pulse, its amplitude and its period (which is equal to the heart period). The level of the variability of each PPG pulse parameter was measured by the ratio of the standard deviation of the parameter to its mean value. The level of the low-frequency fluctuations for the PPG amplitude and for the heart cycle period did not differ between males and females, but was lower for diabetic patients, indicating lower activity of the autonomic nervous system. The curves of the baseline and the amplitude of the PPG signal for the non-diabetic subjects showed high correlation between the left and the right hands. For most of the diabetic patients the right-left correlation coefficients were significantly lower than those for the non-diabetic subjects. Our initial results have shown that the variability of the PPG parameters shows promise for the assessment of the function of the autonomic nervous system.
TL;DR: The results suggest that techniques designed to eliminate negative thought loops can have important positive effects on stress, emotions and key physiological systems, and that relatively inexpensive interventions may dramatically and positively impact individuals’ health and well-being.
Abstract: This study examined the effects on healthy adults of a new emotional self-management program, consisting of two key techniques, “Cut-Thru” and the “Heart Lock-In.” These techniques are designed to eliminate negative thought loops and promote sustained positive emotional states. The hypotheses were that training and practice in these techniques would yield lowered levels of stress and negative emotion and cortisol, while resulting in increased positive emotion and DHEA levels over a one-month period. In addition, we hypothesized that increased coherence in heart rate variability patterns would be observed during the practice of the techniques.
TL;DR: Standardized heart rate analysis carried out in 9 posttraumatic stress disorder patients at rest demonstrated clear-cut evidence of a baseline autonomic hyperarousal state, and the lack of response to the stress model applied in the study appears to imply that PTSD patients experience so great a degree of autonomichyperactivation at rest, that they are unable to marshal a further stressresponse to the recounting of the triggering trauma.
TL;DR: Patients with epilepsy appear to have an altered autonomic control of the heart, with a reduction in some heart-rate variability measures, suggesting a decreased sympathetic tone, which may be related to the drug therapy or the epilepsy as such.
TL;DR: In the hour before AF after CABG surgery, higher heart rate and lower heart rate complexity compared with values in control patients were independent predictors of AF, suggesting the possibility of divergent autonomic conditions before AF onset.
Abstract: Background—Atrial fibrillation/flutter (AF) is a frequent complication of coronary artery bypass graft surgery (CABG) that leads to increased costs and morbidity We hypothesized that heart rate variability (HRV), an indicator of cardiac sympathovagal balance, is altered before the onset of postoperative AF Because nonlinear methods of HRV analysis provide information about heart rate dynamics not evident from usual HRV measures, we also hypothesized that approximate entropy (ApEn), a nonlinear measure of HRV, might have predictive value Methods and Results—Analysis of HRV was performed in 3 sequential 20-minute intervals preceding the onset of postoperative AF (24 episodes in 18 patients) These data were compared with corresponding intervals in 18 sex- and age-matched postoperative control subjects who did not develop AF Patients had left ventricular ejection fractions >45% before surgery and were not receiving β-blockers during ambulatory ECG monitoring after surgery Logistic regression demonstrate
TL;DR: The results support the a priori hypothesis regarding enhanced sympathetic and cardiovascular activity and correlated very highly with lack of perceived emotional social support, reinforcing prior research on the linkage between social isolation and severity of depressive symptoms.
TL;DR: The hypothesis that measures of heart rate power spectra are inversely related and negatively correlated to severity of illness and outcome in critically ill and injured children is supported.
Abstract: Objectives: To determine if decomplexification of heart rate dynamics occurs in critically ill and injured pediatric patients. We hypothesized that heart rate power spectra, a measure of heart rate dynamics, would inversely correlate with measures of severity of illness and outcome.Design: A
Journal Article•
TL;DR: This chapter reviews some of the experimental observations that were instrumental for the novel clinical approach to post-myocardial infarction risk stratification based on the use of autonomic markers as risk stratifiers and focuses on clinical studies with special attention for a very recent multicentre prospective study (ATRAMI).
Abstract: The knowledge progressively accumulated on the relation between changes in autonomic activity and cardiac mortality, particularly in the setting of acute myocardial ischaemia, has turned during the last decade toward the potential prognostic value of markers of autonomic activity. Two of these markers, heart rate variability and baroreflex sensitivity, have gained progressive popularity. This chapter reviews some of the experimental observations that were instrumental for the novel clinical approach to post-myocardial infarction risk stratification based on the use of autonomic markers as risk stratifiers. It then focuses on clinical studies with special attention for a very recent multicentre prospective study (ATRAMI) carried out in almost 1300 post-myocardial infarction patients and aimed at the evaluation of the prognostic value of both heart rate variability and baroreflex sensitivity. Finally, some pathophysiological considerations are added to clarify the legitimacy, or lack of it, of the terminology currently used in clinical studies based on autonomic markers.
TL;DR: The effect of breath rate on the relationship between heart rate and systolic pressure variabilities is a frequency-dependent phenomenon that is also independent of the sympathetic drive.
Abstract: Objective: The aims of this study were to determine the relationships between oscillations in systolic blood pressure and heart period at different breathing frequencies and to investigate the role of sympathetic contribution to this relationship. Methods: Fourteen healthy volunteers underwent three randomized periods of controlled breathing at 6, 10 and 16 breaths/min. ECG (RR), respiratory signal (RESP) and systolic blood pressure (SBP) were continuously recorded. The component of RR and SBP oscillations related to respiration (RRResp and SBPResp) was defined by means of uni- and bivariate spectral analysis. The squared coherence ( K 2) and phase between RR and RESP, and RR and SBP (RR-SBP) were also assessed. When the K 2 of RR-SBP in the respiratory band was >0.5, we considered the phase and calculated the closed-loop gain between the two signals. Seven subjects were also studied after chronic metoprolol treatment. Results: Although the mean values of RR and SBP did not differ between the three periods of breathing, the higher the respiratory rate, the smaller the RRResp and SBPResp. The phase was always negative (SBPResp changes preceded RRResp changes), thus suggesting a baroreflex link. The higher the respiratory rate, the lower the gain and phase. Pharmacological β -adrenoceptor blockade increased the gain and shifted the phase, but the relationships found at baseline between the respiratory rate and both the gain and phase remained unchanged. Conclusions: The effect of breath rate on the relationship between heart rate and systolic pressure variabilities is a frequency-dependent phenomenon that is also independent of the sympathetic drive.
TL;DR: The short-term fractal scaling exponent performed better than other heart rate variability parameters in differentiating patients with coronary artery disease from healthy subjects, but it was not related to the clinical or angiographic severity of coronary arteries disease or any single nonspectral or spectral measure of HR variability in this retrospective study.
Abstract: Dynamic analysis techniques may uncover abnormalities in heart rate (HR) behavior that are not easily detectable with conventional statistical measures. However, the applicability of these new methods for detecting possible abnormalities in HR behavior in various cardiovascular disorders is not well established. Conventional measures of HR variability were compared with short-term ( 11 beats, alpha2) fractal correlation properties and with approximate entropy of RR interval data in 38 patients with stable angina pectoris without previous myocardial infarction or cardiac medication at the time of the study and 38 age-matched healthy controls. The short- and long-term fractal scaling exponents (alpha1, alpha2) were significantly higher in the coronary patients than in the healthy controls (1.34 +/- 0.15 vs 1.11 +/- 0.12 [p <0.001] and 1.10 +/- 0.08 vs 1.04 +/- 0.06 [p <0.01], respectively), and they also had lower approximate entropy (p <0.05), standard deviation of all RR intervals (p <0.01), and high-frequency spectral component of HR variability (p <0.05). The short-term fractal scaling exponent performed better than other heart rate variability parameters in differentiating patients with coronary artery disease from healthy subjects, but it was not related to the clinical or angiographic severity of coronary artery disease or any single nonspectral or spectral measure of HR variability in this retrospective study. Patients with stable angina pectoris have altered fractal properties and reduced complexity in their RR interval dynamics relative to age-matched healthy subjects. Dynamic analysis may complement traditional analyses in detecting altered HR behavior in patients with stable angina pectoris.
Journal Article•
TL;DR: The results suggest that kapalabhati modifies the autonomic status by increasing sympathetic activity with reduced vagal activity and suggests that HRV is a more useful psychophysiological measure than heart rate alone.
Abstract: The heart rate variability (HRV) is an indicator of the cardiac autonomic control. Two spectral components are usually recorded, viz. high frequency (0.15-0.50 Hz), which is due to vagal efferent activity and a low frequency component (0.05-0.15 Hz), due to sympathetic activity. The present study was conducted to study the HRV in two yoga practices which have been previously reported to have opposite effects, viz, sympathetic stimulation (kapalabhati, breathing at high frequency, i.e., 2.0 Hz) and reduced sympathetic activity (nadisuddhi, alternate nostril breathing). Twelve male volunteers (age range, 21 to 33 years) were assessed before and after each practice on separate days. The electrocardiogram (lead I) was digitized on-line and off-line analysis was done. The results showed a significant increase in low frequency (LF) power and LF/HF ratio while high frequency (HF) power was significantly lower following kapalabhati. There were no significant changes following nadisuddhi. The results suggest that kapalabhati modifies the autonomic status by increasing sympathetic activity with reduced vagal activity. The study also suggests that HRV is a more useful psychophysiological measure than heart rate alone.
TL;DR: Control of autonomic cardiac activity at the level of the cerebral cortex seems to be characterized by a division of responsibility between both hemispheres, sympathetic activity being mainly controlled by the right hemisphere and parasympathetic activity being under the left hemisphere's main control.