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PubMed1998

Relationships between heart rate and heart rate variability: study in conscious rats.

Heart rate (HR) and heart rate variability (HRV) are risk markers in cardiac disease. HRV is also an index of the sympathovagal modulation of heart rate. Their relations have been rarely analyzed. We aimed to study such relations in normal adult conscious rats by using a novel bradycardic agent, a sinus node inhibitor, S-16257. Placebo-drug crossover designs were used while monitoring HR with telemetry and analyzing HRV in both time and frequency domains. S-16257 (2 mg/kg; n = 10) decreased HR by 29% and markedly increased HRV in parallel. By using various combinations of S-16257, atropine (2 mg/kg), and propranolol (4 mg/kg), a positive relation was shown between RR interval and various indexes of HRV: the slower the HR, the greater the HRV. Nevertheless, there is one exception to this correlation. When S-16257 was associated with both atropine and propranolol, the deep bradycardia was accompanied by a reduction of HRV, which indicates that the physiologic negative correlation between HR and HRV is not an intrinsic property of the pacemaker but is highly dependent on the two components of the autonomic system.

Animals↗

PubMed1982

Developmental patterns of heart rate and heart rate variability during sleep and waking in normal infants and infants at risk for the sudden infant death syndrome.

The developmental sequence of heart rate and heart rate variability was examined during sleep and waking states in 22 normal infants, and 22 siblings of sudden infant death syndrome (SIDS) victims, using 12-h polygraphic recordings at 1 week and at 1, 2, 3, 4, and 6 months of age. Heart rate was higher in siblings of SIDS victims than in normal infants during quiet sleep over the first 6 months of life and was higher in the waking state at 3 months of age. The sibling group also had lower variability at 1 week during quiet sleep. Gender contributed no significant differences to heart rate, but females at risk for SIDS had lower waking cardiac variability than males.

Child Development↗

PubMed1996

Heart rate and heart rate variability in acute coronary heart disease.

The parameters of cardiac autonomic function, heart period length and heart period length variability were investigated in 70 patients, 50 males and 20 females, mean age 54.8 +/- 9.6 years, admitted to coronary care unit. There were 15 unstable angina patients, 21 anterior wall infarction patients, 20 posterior wall infarction patients, and 14 non-Q-wave infarction patients, who survived to discharge. Heart period length and heart period length variability for each patient were manually measured on the basis of 30 consecutive sinus normal-to-normal RR intervals in ECG every 20 minutes during the initial 24 hours of their stay at the coronary care unit and in the third week after admission. For each interval analyzed, the mean duration of RR interval was computed. RR interval variations were expressed as coefficient of variation (CV). On admission, heart rate was significantly slower (848 +/- 173 ms vs. 837 +/- 163 ms) and CV significantly lower (4.8 +/- 4.2 vs. 5.0 +/- 3.4%) than on discharge (p < 0.01). The significant difference in the mean RR interval between anterior wall infarction patients (802 +/- 186 ms) and inferior wall infarction patients (879 +/- 181 ms) recorded on admission disappeared on discharge from hospital (806 +/- 144 vs. 783 +/- 100 ms). CV was lower in acute myocardial infarction patients (4.7 +/- 3.6; 4.1 +/- 3.2) than in unstable angina patients (5.3 +/- 5.6) on admission (p < 0.05). Heart rate variability was greater in anterior wall infarction patients and unstable angina patients (CV = 5.3 +/- 3.1; 5.2 +/- 3.6%) than in posterior wall infarction patients and non-Q-wave infarction patients (CV = 4.7 +/- 3.5; 4.8 +/- 3.6%). The findings showed that different degrees of cardiac sympathovagal activity may occur in acute coronary heart disease patients during the first 24 hours of their stay at coronary care unit and on discharge from hospital.

Adult↗

PubMed1985

Longitudinal measurements of fetal breathing, body movements, heart rate, and heart rate accelerations and decelerations at 24 to 32 weeks of gestation.

Fetal breathing, fetal body movements, fetal heart rate, and fetal heart rate accelerations and decelerations were studied longitudinally in healthy fetuses between 24 and 32 weeks' gestation in the second and third hour following an 800 kcal maternal meal. The expected increase in fetal breathing following a maternal meal was not seen until fetuses were at 30 to 32 weeks' gestation. The number of body movements decreased and the interaction between body movements and fetal heart rate accelerations became more evident as fetuses became older. Fetal heart rate decelerations increased with gestational age, and the relative proportion of total decelerations that were either associated with body movements or were part of a deceleration/acceleration/deceleration complex increased from 24 to 32 weeks' gestation. The data support the hypothesis that gestational age is an important variable to consider when interpreting biophysical measurements in the human fetus at 24 to 32 weeks' gestation. Fetal body movements may be the single most important measurement of fetal health at these gestational ages.

Adult↗

PubMed2005

Effects of subchronic exposures to concentrated ambient particles (CAPs) in mice. III. Acute and chronic effects of CAPs on heart rate, heart-rate fluctuation, and body temperature.

Normal mice (C57) and mice prone to develop atherosclerosis (ApoE-/-) were implanted with electrocardiograph (EKG), core body temperature, and motion transmitters were exposed daily for 6 h to Tuxedo, NY, concentrated ambient particles (CAPs) for 5 day/wk during the spring and summer of 2003. The series of 5-min EKG monitoring and body-temperature measurements were obtained for each animal in the CAPs and filtered air sham exposure groups. Our hypothesis was that chronic exposure could cause cumulative health effects. We used our recently developed nonparametric method to estimate the daily time periods that mean heart rates (HR), body temperature, and physical activity differed significantly between the CAPs and sham exposed group. CAPs exposure most affected heart rate between 1:30 a.m. and 4:30 a.m. With the response variables being the average heart rate, body temperature, and physical activity, we adopted a two-stage modeling approach to obtain the estimates of chronic and acute effects on the changes of these three response variables. In the first stage, a time-varying model estimated daily crude effects. In the second stage, the true means of the estimated crude effects were modeled with a polynominal function of time for chronic effects, a linear term of daily CAPs exposure concentrations for acute effects, and a random component for unknown noise. A Bayesian framework combined these two stages. There were significant decreasing patterns of HR, body temperature, and physical activity for the ApoE-/- mice over the 5 mo of CAPs exposure, with smaller and nonsignificant changes for the C57 mice. The chronic effect changes of the three response variables for ApoE-/- mice were maximal in the last few weeks. There was also a significant relationship between CAPs exposure concentration and short-term changes of heart rate in ApoE-/- mice during exposure. Response variables were also defined for examining fluctuations of 5-min heart rates within long (i.e., 3-6 h) and short time periods (i.e., approximately 15 min). The results for the ApoE-/- mice showed that heart-rate fluctuation within the longer periods increased to 1.35-fold by the end of exposure experiment, while the heart-rate fluctuation within 15 min decreased to 0.7-fold.

Air Pollutants↗

PubMed2000

Maturational changes in heart rate and heart rate variability in low birth weight infants.

To provide insight into the maturation of neural mechanisms responsible for variability in heart rate during quiet and active sleep, 6-hour continuous electrocardiographic recordings and simultaneous minute-by-minute behavioral activity state assignments were performed in 61 healthy, growing low birth weight infants. The infants weighed 795-1600 g at birth and ranged between 31-38 weeks in postconceptional age. During this age interval there was a decrease in heart rate during quiet sleep and an increase in both time domain and frequency domain measures of the variability in cardiac interbeat intervals. In quiet sleep, global variability, measured as SD of R-R intervals, increased in relation to age, as did higher frequency variability, measured as the square root of the mean of squared successive differences in R-R intervals. Developmental changes in the 0.5-2.0 Hz spectral power band of RR-interval variability, another measure of high frequency variability, paralleled the changes seen in the time domain measure. Evaluation of patterns of changes in the magnitude and direction of successive interbeat intervals provided evidence that the incidence of sustained accelerations or decelerations increased whereas the incidence of no change in consecutive RR-intervals decreased as infants matured. Among the various measures of heart rate variability, the incidence of sustained change and no change in successive interbeat intervals were most closely related to postconceptional age in both sleep states. The overall decrease in heart rate, increase in heart rate variability, and increase in the pattern of changes in interbeat interval with postconceptional age are consistent with the maturation of the autonomic cardio-regulatory activity from 31-38 weeks age.

Electrocardiography↗

PubMed2006

Changes in heart rate and heart rate variability in Thoroughbreds during prolonged road transportation.

OBJECTIVE: To determine whether evaluation of heart rate (HR) and HR variability (HRV) during prolonged road transportation in horses provides a sensitive index of autonomic stimulation. ANIMALS: Five 2-year-old Thoroughbreds. PROCEDURE: ECGs were recorded as horses were transported for 21 hours in a 9-horse van. Heart rate, high-frequency (HF) power, low-frequency (LF) power, and LF-to-HF ratio from Fourier spectral analyses of ECGs were calculated and compared with values recorded during a 24-hour period of stall rest preceding transportation. RESULTS: HR, HF power, and LF power had diurnal rhythms during stall rest but not during road transportation. Heart rate was higher and HF power and LF power lower during road transportation than stall rest, and HR, HF power, LF power, and LF-to-HF ratio all decreased with time during road transportation. Heart rate during stall rest was weakly and inversely associated with LF power, but during road transportation was strongly associated with LF power, HF power, and LF-to-HF ratio. Neither LF power nor HF power was correlated with LF-to-HF ratio during stall rest, but LF power was strongly and HF power weakly correlated with LF-to-HF ratio during road transportation. High-frequency power and LF power were significantly correlated with each other during stall rest and road transportation. Heart rate was significantly influenced by LF power and LF-to-HF ratio during stall rest (R(2) = 0.40) and by HF power and LF-to-HF ratio during road transportation (R(2) = 0.86). CONCLUSIONS AND CLINICAL RELEVANCE: HR is influenced by different sympathovagal mechanisms during stall rest, compared with during road transportation; HRV may be a sensitive indicator of stress in transported horses.

Animals↗

PubMed1975

Correlation of fetal heart rate, maternal heart rate, and age of pregnancy.

External fetal electrocardiography was performed in three groups of normal pregnant patients delivered of normal newborn infants. Maternal and fetal heart rates were compared and maternal heart rates in the three trimesters were analyzed. Mean heart rates, as well as standard deviations of the three groups, were compared in mother and fetus. The results confirm previous work establishing the independence of fetal and maternal heart rates in the absence of maternal hemodynamic changes mediated by various factors.

Electrocardiography↗

PubMed2002

Effects of alcohol intake on ambulatory blood pressure, heart rate, and heart rate variability in Japanese men with different ALDH2 genotypes.

The effects of alcohol intake on haemodynamics and heart rate variability were investigated with relation to genotypes of aldehyde dehydrogenase 2 (ALDH2), which were determined in 33 male Japanese volunteers (mean +/- s.e., 35.7 +/- 1.4 years) using the PCR-RFLP method. On the alcohol intake day, they consumed 660 ml of beer containing 33 ml of ethanol (0.3-0.5 g/kg of body weight) from 18.00 to 18.30. On the control day, they ingested the same amount of non-alcoholic beer. Ambulatory blood pressure, heart rate, and ECG R-R intervals were measured during a 24-h period with a portable recorder. A power spectral analysis of R-R intervals was performed to obtain the low-frequency (LF) and high-frequency (HF) components. Sixteen subjects were homozygotes for the normal ALDH gene (active ALDH2), only one was a homozygote for the mutant ALDH2 gene (inactive ALDH2), and the remaining 16 were heterozygotes (inactive ALDH2). Alcohol intake did not change 24-h average blood pressure (BP) either in the active ALDH2 group or in the inactive ALDH2 group. However, during the time interval from 18.30 to 0.00, alcohol intake significantly decreased diastolic BP in the active ALDH2 group and both systolic and diastolic BPs in the inactive ALDH2 group. In the active ALDH2 group, alcohol intake did not change heart rate, while in the inactive ALDH2 group, alcohol intake significantly increased 24-h average heart rate by 5.3 +/- 1.6 beats per minute (P < 0.01). In the active ALDH2 group, neither the LF nor the HF component was changed by alcohol intake, while in the inactive ALDH2 group, both the LF and the HF components were significantly decreased during the time interval from 18.30 to 0.00. These results demonstrate for the first time that ALDH2 genotypes modify the effects of intake of a small amount of alcohol on haemodynamics and heart rate variability in Japanese men.

Adult↗

PubMed2005

Heart rate and heart rate variability of healthy cats in home and hospital environments.

To investigate heart rate and its variability, a telemetry device was affixed to 16 healthy, young cats. Prior to inclusion in the study, cats were subject to echocardiographic examination. The heart rate (HR) when cats were restrained for echocardiography (HR(r)) was calculated from 4-5 consecutive RR intervals obtained from a simultaneously recorded electrocardiogram. Electrocardiographic data were then acquired by telemetry in a quiet room in the veterinary hospital (VTH) and later, in the owner's home (home). The ambulatory data were digitally sampled and the RR interval tachogram from a 4 min epoch subject to Fast Fourier Transform to yield measures of heart rate variability (HRV). Sinus arrhythmia was often observed in resting cats. Heart rates (bpm) expressed as mean (+/-SD) were: HRr: 187 (+/-25), HRVTH: 150 (+/-23), HR(home): 132 (+/-19); each of these rates was significantly different from the others. Significant differences in profiles of HRV suggested that sympathetic tone was higher (and parasympathetic tone lower) when cats were in the hospital.

Animals↗

PubMed1994

Heart rate and heart rate variability as indexes of sympathovagal balance.

According to the Rosenblueth-Simeone model, the heart rate (HR) is proportional to the sympathovagal balance. The individual proportionality constant is the intrinsic heart rate, which can only be determined invasively. The normalized low-frequency heart rate variability power (LF) has been raised as a calibrated noninvasive alternative. To concrete this assumption, we studied the individual LF-HR relation during incremental head-up tilt (0, 10, 20, 30, 40, 45, 50, 55, 60, 65, 70, 75, and 80 degrees) in 21 young, healthy males. HR (means +/- SD) increased from 61.0 +/- 9.1 beats/min at 0 degree to 85.9 +/- 18.3 beats/min at 80 degrees. LF increased from 45.8 +/- 16.7 nu at 0 degrees to 79.8 +/- 13.8 nu at 80 degrees (nu meaning normalized units). Individual regressions of LF on HR yielded correlation coefficients of 0.80 +/- 0.13 (means +/- SD). The demonstrated linear relation between LF and HR confirms the potential significance of heart rate variability as a noninvasive means of assessing the sympathovagal balance.

Adult↗

PubMed1996

Heart rate and heart rate variability changes induced by right atrial pacing.

This research was conducted to determine (1) whether heart rate and R-R interval variability are modified by atrial pacing, and (2) whether these changes (if they do occur) are related to the inducibility of tachyarrhythmias during electrophysiological studies. We studied 42 patients who were referred for electrophysiological evaluation of supraventricular (n = 16) or ventricular arrhythmias (n = 26). The patients studied for the evaluation of ventricular arrhythmias had structural and functional cardiac damage. The patients evaluated because of supraventricular arrhythmias had normal ejection fraction and on structural cardiac damage. In these patients a significant decrease in R-R interval (P = 0.0002) and in its standard deviation (P < 0.005) was observed following atrial pacing. No significant heart rate or R-R interval standard deviation change was observed after pacing in the patients with structural heart disease. The heart rate or R-R interval variability changes did not allow us to discriminate the patients with inducible ventricular arrhythmias from those without such arrhythmias. We conclude that right atrial pacing induces a heart rate increase and R-R variability decrease in patients without heart disease. In patients with cardiac damage the responses are blunted, and do not permit the identification of patients who have ventricular arrhythmias inducible by means of electrophysiological studies.

Adult↗

PubMed1997

Heart rate and heart rate variability, a pharmacological target.

Heart rate varies with respiration, blood pressure, emotion, etc., and heart rate variability (HRV) is presently one of the best indices to predict fatal issues in cardiac failure and after myocardial infarction. HRV depends on various reflexes. In addition, parallel studies of HRV and the myocardial adrenergic and muscarinic transduction system in experimental models of cardiac hypertrophy (CH) have suggested that the myocardial phenotype at the sinus-node level may also play a role. A transgenic strain of mice with atrial overexpression of the beta 1-adrenergic receptors was generated with attenuated HRV, which demonstrates that the phenotype itself is a determinant of HRV. HRV is explored by noninvasive techniques, including simple determination of the standard error of the mean, time-domain analysis, and Fourier transformation. We recently developed a time and frequency domain method of analysis, the smoothed pseudo-Wigner-Ville transformation, which allows better exploration of nonstationarity. Nonlinear methods have also been applied due to the extreme complexity of the biological determinants, and have provided evidence of a chaotic attractor in certain conditions. It is proposed that in steady state a very simple process, which is not completely deterministic, could better explain intermit interval regulations than chaotic behavior. In contrast, under extreme circumstances the regulation proceeds using chaotic behavior. Arrhythmias and HRV can be quantitated in 16-month-old unanesthetized spontaneously hypertensive rats (SHR). Ventricular premature beats are more frequent in SHR than in age-matched controls; they disappear after converting enzyme inhibition (CEI) relative to the reduction of both cardiac hypertrophy and ventricular fibrosis. HRV is attenuated in SHR, as it is in compensatory CH in humans. When CH is prevented, HRV returns to normal. CEI is therefore antiarrhythmic. Another pharmacological application of this concept concerns the bradycardic agents that may improve HRV.

Animals↗

PubMed2026

Modulation of heart rate and heart rate variability during animal-assisted treatment of patients in a minimally conscious state: A randomized controlled crossover study.

BACKGROUND: Animal-assisted treatment (AATx) is a promising and increasingly used approach in neurorehabilitation, yet its psychophysiological effects remain largely unexplored. Patients in a minimally conscious state (MCS) show severely altered consciousness with minimal but definite behavioral signs of awareness. Because behavioral assessment in this population is limited, psychophysiological measures such as heart rate (HR) and heart rate variability (HRV) may offer valuable insights into autonomic regulation during therapy. AIM: The present study investigated whether AATx influences HR and HRV compared to treatment as usual (TAU). METHODS: A randomized controlled crossover design with repeated measures was conducted. HR and HRV data were recorded using an Empatica E4 wristband, and linear mixed-effects models were fitted for each outcome variable. The analytic sample included twenty-one patients with MCS who completed at least one of the four sessions. RESULTS: We found a significant decrease in mean HR (estimate = -12.75, p = .041) and a significant increase in the standard deviation of normal-to-normal intervals (SDNN) (estimate = 15.76, p = .020) during AATx compared to TAU from the pretreatment to the posttreatment phase, indicating enhanced parasympathetic activation and greater autonomic flexibility. Other HRV parameters revealed no significant effects of AATx, though trends were consistent with the hypotheses. CONCLUSIONS: These findings provide preliminary physiological evidence that AATx can modulate autonomic activity in MCS patients. Despite limitations related to sample size and recording quality, the results highlight the potential of AATx as an emotionally engaging intervention in early neurorehabilitation.

Humans↗

PubMed2004

Heart rate and heart rate variability in chicken embryos at the end of incubation.

Our immediate goal was to study heart rate variability (HRV) in chicken embryos in the egg. Instantaneous heart rate data were needed for this purpose, and accordingly an ECG recording method in the egg was developed. The aim of this work was to test the hypothesis that autonomic nervous cardiac modulation, as shown from HRV parameters, is present at the end of development and that it reaches a constant value during the last days of incubation. Embryonic chicken heart rate was obtained at the final incubation period (days 19 and 20) from ECG recordings. Tachograms were computed and time- and frequency-domain indices of HRV were determined. No significant differences were found between HRV indices from day 19 and day 20. The power spectra extended in two frequency bands with centre frequency around 0.6-0.7 Hz (low frequency (LF) component), and another around 1.2-1.5 Hz (high frequency (HF) component); the latter was shown to reflect respiratory sinus arrhythmia. A relation between mean RR interval and some HRV parameters (rMSSD, pNN5 and HF power) was shown. HRV results obtained from embryonic chickens, showed the presence of modulation of cardiovascular function by the autonomic nervous system. The results suggested that sympathetic and parasympathetic activities have already reached a constant level at day 19 of incubation. High frequency oscillations (0.78-2.5 Hz) were detected and are considered to reflect respiratory sinus arrhythmia.

Animals↗

PubMed1999

Effect of intravenous magnesium on heart rate and heart rate variability in patients with chronic atrial fibrillation.

The present double-blind, placebo-controlled study investigated the effects of intravenous magnesium on heart rate and rate variability in 30 patients with chronic atrial fibrillation. During standardized conditions, intraindividual variation in heart rate and rate variability was low in patients with chronic atrial fibrillation and magnesium had no effect on heart rate or rate variability.

Aged↗

PubMed2003

Prospective association between hormone replacement therapy, heart rate, and heart rate variability. The Atherosclerosis risk in communities study.

Hormone replacement therapy is universally associated with coronary heart disease (CHD) in observational studies, but it is unknown whether this association is mediated by the autonomic nervous system. We tested the hypothesis that postmenopausal hormone replacement therapy was associated with more favorable heart rate (HR) and heart rate variability (HRV) in a population sample of women (n=2,621). Hormone therapy use was measured at four examinations beginning in 1987. Supine HR and HRV indices were measured for 6 minutes at the final examination (1996-1998). In unadjusted linear regression models, hormone therapy was associated with lower HR (hormone use=64.7 vs. never=65.7 beats/min, P=.01) and higher HRV. However, following adjustment for age and CHD risk factors, both associations were eliminated. Results from this observational study suggest that hormone therapy is not associated with HR or HRV. These analyses should be replicated in a randomized trial.

Autonomic Nervous System↗

PubMed1996

Correlative studies of heart rate and heart rate variability indices from five consecutive ambulatory electrocardiogram recordings in patients with coronary artery disease.

BACKGROUND: Reproducibility of heart rate (HR) and heart rate variability (HRV) indices from ambulatory electrocardiograms (AECGs) is a prerequisite for their use as predictors or monitors of disease progression, or response to therapeutic interventions. HYPOTHESIS: This study sought to determine the stability over time of HR and HRV indices in patients with coronary artery disease. METHODS: Five AECGs, recorded at 1-week intervals in 21 clinically stable patients, were used to calculate minimum, average, and maximum HR, and three commonly used HRV indices in data samples of 15, 30, 60, 120, daytime and nighttime intervals (complete data were available on 17 patients). RESULTS: All parameters studied were stable over time (p = NS). Diurnal variation was found only for the average and maximum HR, with values being higher for daytime than for nighttime. Intercorrelations of the HR and HRV indices were poor and varied among the five AECGs, suggesting that these parameters reflect different aspects of HRV. The HR and HRV variables calculated from short-time intervals correlated poorly with the corresponding information from 24-h recordings, and such relationships varied among the five AECGs. CONCLUSIONS: Thus, HR and HRV indices from five consecutive AECGs recorded at 1-week intervals are reproducible. The poor intercorrelations between pairs of the studied indices suggest that none of these parameters can be used as surrogate of the others. Finally, the poor performance of HR and HRV indices, deriving from short-time intervals, indicate that they cannot be employed in lieu of parameters calculated from 24-h AECGs.

Aged↗