Circadian rhythm of heart rate and heart rate variability.

BACKGROUND: Measurements of heart rate variability (HRV) are increasingly used as markers of cardiac autonomic activity. AIM: To examine circadian variation in heart rate and HRV in children. SUBJECTS: A total of 57 healthy infants and children, aged 2 months to 15 years, underwent ambulatory 24 hour Holter recording. Monitoring was also performed on five teenagers with diabetes mellitus and subclinical vagal neuropathy in order to identify the origin of the circadian variation in HRV. METHODS: The following variables were determined hourly: mean RR interval, four time domain (SDNN, SDNNi, rMSSD, and pNN50) and four frequency domain indices (very low, low and high frequency indices, low to high frequency ratio). A chronobiological analysis was made by cosinor method for each variable. RESULTS: A significant circadian variation in heart rate and HRV was present from late infancy or early childhood, characterised by a rise during sleep, except for the low to high frequency ratio that increased during daytime. The appearance of these circadian rhythms was associated with sleep maturation. Time of peak variability did not depend on age. Circadian variation was normal in patients with diabetes mellitus. CONCLUSION: We have identified a circadian rhythm of heart rate and HRV in infants and children. Our data confirm a progressive maturation of the autonomic nervous system and support the hypothesis that the organisation of sleep, associated with sympathetic withdrawal, is responsible for these rhythms.     

Heart rate variability and circadian variations in type 1 diabetes mellitus

Diabetic autonomic neuropathy (DAN) commonly complicates diabetes and is associated with increased mortality rates over 5 yr. This fact denotes the significance of DAN prevention, mainly with effective glycemic control. However, total prevention of autonomic neuropathy in diabetic patients is not achievable. Thus, the timely detection of DAN and the use of effective means to improve autonomic nervous system function or slow down its progression become of utmost significance. Heart rate variability (HRV) is a technique that measures the beat-to-beat variability in RR intervals, which reflects changes in autonomic activity and their impact on cardiovascular function. Circadian variation in time and frequency domains of heart variability has been shown to correlate with circadian rhythm of ambulatory ischemia and suggests that relative changes in vagal and sympathetic tone at different times during the day may have a direct relationship to the severity of clinical events. Forty-seven (21 boys and 26 girls) type I insulin-dependent diabetics and 46 control subjects (19 boys and 27 girls) were included in the study. Our investigation demonstrated that overall HRV is markedly depressed in diabetes mellitus (DM). All time domain parameters except standard deviation of all 5-min mean RR intervals and all frequency domain indices maintain significant circadian variation. These changes in overall HRV and HRV circadian rhythms reflect significant reductions in cardiac parasympathetic activity and, possibly, increased sympathetic tone.     

Heart rate variability in diabetic children: Sensitivity of the time- and frequency-domain methods

Summary Heart rate variability (HRV) is a noninvasive index of the neural activity of the heart. Although also influenced by the sympathetic activity of the heart, HRV is essentially determined by the vagal stimulation of the heart. Several HRV abnormalities have been described in adults with diabetes mellitus. However, there are few data on HRV in children with diabetes mellitus. In the present study, HRV was assessed in seven healthy children, 10 diabetic children with good glycemic control and 11 diabetic children with poor glycemic control. All had normal standard cardiac autonomic function tests, obtained from 24-h Holter tapes. HRV was measured by calculating six time-domain (mean R-R interval (RR), standard deviation of the R-R interval [SDRR], standard deviation of the mean of 288 R-R intervals [SDANN], the mean of the 288 standard deviations computed for each 5-min period [SD], percentage of differences of adjacent R-R intervals of >50 msec for the entire 24 h [pNN50], and the root mean square of successive differences [rMSSD]) and four frequency-domain (low frequency [LF], high frequency [HF], total heart rate power spectra, and LF/HF ratio) indexes. SD, pNN50, rMSSD, LF, HF and total heart rate power spectra were markedly and significantly reduced in diabetic children with poor metabolic control. The 24-h variation of low- and high-frequency components of heart rate power spectra of the latter children had a differet shape. Thus, diabetic children with poor metabolic control (elevated HbA₁c and B₂M levels) have a low HRV compared to those diabetic children with good control and healthy chidren. These results can be interpreted as evidence of cardiac autonomic neuropathy in diabetic children with asymptomatic diabetic autonomic neuropathy.     

Heart rate variability analysis in full-term infants: spectral indices for study of neonatal cardiorespiratory control

The heart rate and respirations of twenty healthy full-term infants between 30 and 60 h postnatal age were studied during quiet sleep with the objective of defining spectral indices which represent normal neonatal heart rate variability (HRV) characteristics. Total HRV power and the distribution of power across different frequency bands varied considerably among infants. Cluster analysis on the measured variables indicated that the population divided into two groups that represented significantly different patterns of HRV behavior. In one group (11 subjects), infants had lower breathing rates and HRV power in a band about the respiration frequency [respiratory sinus arrhythmia (RSA) band] was more than 20% of the total power (TP). Additionally, the ratio of low frequency band power to RSA band power was less than 4. The other group of neonates (nine subjects) had relatively higher breathing rates, RSA power less than 20% of total power, and low frequency to RSA power ratio greater than 4. Regression analysis of low frequency versus TP and RSA versus TP graphs gave strong support to the hypothesis that there were indeed two distinct patterns of HRV behavior. Separation of apparently normal neonates into two groups may be attributed partially to differences in respiratory rates and breathing patterns. However, it is possible that differences in the balance between sympathetic and parasympathetic nervous system control, perhaps related to autonomic maturation, also contribute to group separation. The indices developed from HRV spectral analysis in this investigation may be of value in the study of cardiorespiratory control in neonates.     

Heart rate variability in response to the sleep-related movements in infants with and without colic

The activity of the autonomic nervous system depends on sleep stage. The imbalance of the autonomic nervous system together with over-reactivity to stimuli has been suggested to be an etiologic factor for infantile colic. This study was designed to estimate the reactivity of the autonomic nervous system to a sleep-time stimulus in non-rapid eye movement (NREM) and rapid eye movement (REM) sleep stages and in colic and control infants. Overnight sleep polygraphic recordings were performed for 12 colic and 14 control infants at the age of 8 weeks. Movements were detected by a static-charge-sensitive bed. Extent of heart rate variability (HRV) was measured in response to spontaneous sleep-related movements. HRV analysis was performed over 2-min segments during NREM and REM sleep before and after 5-36-s long movement periods. Total (0.04-1.0 Hz), low (0.04-0.15 Hz) and high frequency (0.15-1.0 Hz) HRV increased after the movement periods in light NREM sleep (p < 0.001). These changes were not observed in REM sleep. No differences were found between the colic and the control groups in HRV. The observed difference in the response of the HRV between sleep stages is likely to reflect the different characteristics of heart rate control in NREM and REM sleep, but our results do not suggest that colic infants would have abnormal autonomic reactivity to stimuli while asleep.     

甲状腺功能亢进症儿童的甲状腺激素与心率减速力及心率变异性的相关性

目的 对甲状腺功能亢进症（简称“甲亢”）儿童的心率减速力（DC）、心率加速力（AC）、心率变异性（HRV）进行分析,并探讨甲亢儿童的血清甲状腺激素水平与DC、AC及HRV的关系。方法 选取甲亢儿童47例,另选取50例健康儿童为对照组,对所有受试者行24 h动态心电图检查,将甲亢组与对照组的DC、AC、心率（HR）及HRV各指标[RR间期总体标准差（SDNN）、RR间期平均值的标准差（SDANN）、相邻RR间期差值的均方根（RMSSD）、低频功率（LF）、高频功率（HF）]进行比较,并将甲亢儿童的甲状腺激素指标[游离三碘甲状腺原氨酸（FT3）、游离甲状腺素（FT4）]与DC、AC及HRV各指标进行相关性分析。结果 甲亢组的DC、SDNN、SDANN、RMSSD、LF、HF均低于对照组;AC和HR均高于对照组（P < 0.05）。甲亢儿童的血清FT3、FT4与DC、SDNN、SDANN、RMSSD、LF、HF均呈负相关（P < 0.05）;与AC和HR呈正相关（P < 0.05）。结论 甲亢儿童的心脏自主神经功能受损,表现为迷走神经张力降低。血清甲状腺激素水平越高,迷走神经张力越低,提示发生心血管疾病的危险性越大。     

Clinical and haemodynamic correlates of heart rate variability in children with congenital heart disease

Heart rate variability (HRV) represents a noninvasive parameter for studying the autonomic control of the heart. Cardiac patients have a complex autonomic disturbance. The relation of HRV to this abnormality in children with congenital heart disease (CHD) has not yet been examined. The present study examined HRV indices from 24 h Holter recordings in 258 children with an operated or non-operated CHD, to determine their differences as an indicator of the severity of heart disease. The latter was defined clinically as New York Heart Association (NYHA) functional class I to IV and haemodynamically by invasive parameters. Five time-domain measures (SDNN, SDNNi, SDANNi, rMSSD and pNN50) and three frequency-domain measures (LF, HF and balance LF/HF) were compared with normal ranges. HRV was reduced in children with CHD, except in patients of NYHA class I. The level of reduction depended on the NYHA functional class. None of the measures was significantly related to haemodynamic data. Conclusion Heart rate variability is reduced in children with Congenital heart disease depending on the functional limitation but not on haemodynamic disturbances. Heart rate variability indices are sensitive markers of the clinical state. Received: 3 December 1997 / Accepted in revised form: 22 June 1998     

Longitudinal assessment of heart rate variability in very low birth weight infants during their NICU stay

BACKGROUND: Maturation of the autonomic nervous system has not been studied in high-risk very low birth weight (VLBW) infants in the first few weeks of life. AIM: To characterize developmental changes in autonomic nervous system activity of high-risk VLBW infants from 23 to 38 weeks post-menstrual age by measuring heart rate variability (HRV). STUDY DESIGN AND SUBJECTS: In this prospective cohort study 38 infants admitted to Children's Memorial Hermann Hospital NICU were longitudinally followed weekly or biweekly. Heart period data were recorded while infants were resting in active sleep. OUTCOME MEASURES: Growth of spectral power of HRV in low-frequency (0.05-0.25 Hz) and high-frequency (0.25-1.00 Hz) bands was modeled with linear mixed-effects models. The high-frequency power provides a measure of respiratory sinus arrhythmia (RSA). RESULTS: Low-frequency power increases with post-menstrual age, and intubated infants have lower HRV. The increase in low-frequency power is faster (0.50+/-0.12 dB/week) than the increase in RSA (0.17+/-0.09 dB/week). CONCLUSION: This longitudinal data exhibits developmental maturation of the RSA and of the low-frequency power of HRV in high-risk VLBW infants.     

The development of autonomic cardiovascular control is altered by preterm birth

Objectives

Autonomic dysfunction, either sympathetic or parasympathetic, may explain the increased incidence of Sudden Infant Death Syndrome (SIDS) among preterm infants, as well as their subsequent heightened risk of hypertension in adulthood. As little is known about the development of autonomic function in preterm infants, we contrasted autonomic cardiovascular control across the first 6 months after term-corrected age (CA) in preterm and term infants.

Study design

Preterm (n = 25) and age matched term infants (n = 31) were studied at 2–4 weeks, 2–3 months and 5–6 months CA using daytime polysomnography. Blood pressure and heart rate were measured during quiet (QS) and active (AS) sleep. Autonomic control was assessed using spectral indices of blood pressure and heart rate variability (BPV and HRV) in ranges of low frequency (LF, reflecting sympathetic + parasympathetic activity), high frequency (HF, respiratory-mediated changes + parasympathetic activity), and LF/HF ratio (sympatho-vagal balance).

Results

In preterm infants, HF HRV increased, LF/HF HRV decreased and LF BPV decreased with age (p < 0.05); these changes were most evident in AS. Compared to term infants, preterm infants in QS exhibited lower LF, HF and total HRV at 5–6 months; higher HF BPV at all ages; and lower LF BPV at 2–4 weeks (p < 0.05).

Conclusions

With maturation, in preterm infants, parasympathetic modulation of the heart increases while sympathetic modulation of blood pressure decreases. Compared to term infants, preterm infants exhibit lesser parasympathetic modulation of the heart along with greater respiratory-mediated changes and lower sympathetic modulation of blood pressure. Impaired autonomic control in preterm infants may increase their risk of cardiovascular dysfunction later in life.     

Sleep position,autonomic function,and arousal

AIMS—To investigate and compare heart rate variability (HRV) and responses of heart rate and arousal to head-up tilting in infants sleeping prone and supine.
METHODS—Thirty seven healthy infants aged 2-4 months were studied. HRV was measured for 500 beats while they were in a horizontal position. Subjects were then tilted 60° head-up, and heart rate recorded over 1 minute and arousal responses observed. Data were collected during both quiet and active sleep for both prone and supine sleep positions.
RESULTS—HRV, as assessed by the point dispersion of Poincaré plots, was significantly reduced in the prone position for both sleep states. Sleep position did not influence the changes in heart rate seen during a head-up tilt. Full awakening to the tilt was common in active sleep but significantly less so in the prone position (15% of prone tests vs 54% supine). Full awakening to the tilt rarely occurred during quiet sleep in either sleep position.
CONCLUSION—This study provides some evidence that blunted arousal responses and/or altered autonomic function are a feature of the prone sleeping position. Decreased HRV may be a sign of autonomic impairment. It is seen in many disease states and in infants who later die of sudden infant death syndrome (SIDS).

     

Factors affecting heart rate variability and heart rate responses to tilting in infants aged 1 and 3 months

Heart rate variability (HRV) and heart rate (HR) responses following a 60 degree head-up tilt were measured in 60 infants at 1 and 3 mo of age to investigate the effects on these of age, sleep state, sleep position, and mother's smoking status. HRV was determined from Poincaré plots of 500 sequential RR intervals to measure overall variability derived from the SDRR of this plot, and instantaneous variability derived from the SDdeltaRR. HR responses to the tilt were measured as changes in RR interval length from rest to immediately following the tilt and again once a stable pattern was reached. SDRR and SDdeltaRR increased 20 and 40%, respectively, with age (p < 0.0001), SDRR was higher in active sleep (AS) than quiet sleep (QS, +72%, p < 0.0001) but both measures of variability (SDRR and SDdeltaRR) were lower in the prone position compared with supine (-18%, p < 0.0001). However, several findings were dependent on the basal RR interval, thus the age effect disappeared once RR interval was taken into account, sleep state remained an important factor and the lower variability when prone now became a difference of -3% (p = 0.034). The tilt generally provoked a reflex tachycardia followed by a bradycardia and settling to a stable HR level below, at, or above baseline within 30 s. The more unusual responses were no HR change, sustained tachycardia or sustained bradycardia (15% of total). These were more likely to occur in younger infants (p = 0.008) and in AS (p < 0.0001). No changes were seen in any of the cardiac indices related to maternal smoking status. The findings confirm several reports indicating that prone sleeping damps some physiologic responses. The data emphasize the need to consider basal heart rate, and sleep position as well as sleep state in autonomic function testing during infant sleep.     

Heart rate turbulence in children--age and heart rate relationships

Heart rate turbulence (HRT) is a chronotropic response of the sinus heart rhythm to ventricular premature beat (VPB). Children show decreasing heart rate together with the maturation of the autonomic nervous system. The aim of the research was to assess the relationship between HRT parameters, age, and heart rate and time domain heart rate variability (HRV) parameters in healthy children. Twenty-four-hour ECG Holter recording was performed on 398 healthy children. The mean RR interval preceding VPB, number of VPBs, and HRT parameters-turbulence onset (TO) and turbulence slope (TS)-were determined. We observed significant correlation among TS and mean RR and age. Children with prepubertal status have lower values of TS compared with those during puberty. According to given quartiles, upper for TO was > or =-0.8%, lower for TS was < or =4.56 ms/RR, 13 patients (3%) obtained abnormal both TO and TS. The correlations between HRT and HRV parameters were observed among the youngest children. Age and heart rate preceding VPB have no effect on HRT onset in children, whereas HRT slope is highly dependent on these variables. Our results support hypothesis that in older children HRT is dependent on autonomic tone and also determined by other intrinsic modulators.     

心率变异性分析有助于对儿童不明原因心悸的诊断

目的：心率变异性作为评价患儿心率变异程度的量化指标,临床上应用越来越广泛。该研究的目的是探讨不明原因心悸患儿心率变异性(HRV)的特点,为心悸患儿的临床诊断提供参考。方法：对34例不明原因心悸患儿,27例正常儿童进行动态心电图检查,分析动态心电图的STT变化及心率的昼夜节律变化,心率变异性时域指标两两比较。结果：心悸患儿时域指标相邻正常RR间期均数的标准差(SDNN)、相邻正常RR间期差值的均方根(RMSSD)、相邻正常RR间期差值大于50ms的个数占总心博数的百分比(PNN50)降低,与对照组相比差异有显著性(P<0.05)。其中15例患儿STT改变的特点符合β受体功能亢进症的诊断标准。结论：不明原因心悸患儿的心率变异性时域指标SDNN,RMSSD,PNN50均有下降,结合STT改变的特点,心率变异性分析可为临床诊断β受体功能亢进症和心脏神经官能症提供参考。     

Impact of thermal vasomotor control on the heart rate variability of newborn infants

The reactivity of the periodic heart rate variability (HRV) to the thermal vasomotor control was studied during quiet sleep in a total of 20 neonates which were classified in 5 groups according to their maturity. Thermal stimulation on the peripheral skin was applied by an air blower at the rates of 5, 2.5 and 1.5 cycles/min. The oscillation of successive R-R intervals of the ECG was determined by a hybrid computer technique during thermal stimulations and compared to spontaneous HRV activity. The indices of the HRV and the total power of the periodic HRV remained unchanged during thermal stimulations. The response of the periodic HRV was selective at the spectral band corresponding to the frequency of stimulation. It was maximal at 5 cycles/min. The relative response was highly significant (P < 0.001) and it increased with increasing maturity. The state of SGA (small for gestational age) seemed to decrease the vasomotor response of the HRV. The results suggested that the thermal vasomotor control was functional already in small preterm infants and it tended to increase with increasing maturity as does the autonomic cardiac control in general.     

Low maternal vitamin B12 status during pregnancy is associated with reduced heart rate variability indices in young children

Vitamin B12 plays a vital role in neuronal development, particularly in myelinogenesis. Demyelination of the autonomic nervous system occurs early in vitamin B12 deficiency. However, the impact of maternal vitamin B12 deficiency during pregnancy on neuronal function in the offspring is poorly documented. The objective of this study was to assess cardiac autonomic nervous activity in children born to mothers with low vitamin B12 status during pregnancy using heart rate variability (HRV) indices in the frequency domain. Seventy‐nine healthy children between 3 and 8 years of age were evaluated from an ongoing birth cohort. The blood sample of the mother had been stored and was analysed for plasma vitamin B12 following enrolment of the child. Subjects were divided, based on the median maternal first trimester vitamin B12 status (114 pmol L^?1), into lower (n = 40) and higher (n = 39) vitamin B12 status groups. A lead II electrocardiogram was recorded in the supine posture and subjected to HRV analysis. Low‐frequency HRV in absolute units was reduced significantly in children of the lower vitamin B12 status group (P = 0.03) and was 53% that of the higher vitamin B12 status group. There was a significant association between low‐frequency and total power HRV with cord blood vitamin B12 levels (ρ = 0.31 and 0.30, both P = 0.03). In summary, children born to mothers with a lower vitamin B12 status have a reduced cardiac sympathetic activity. The long‐term implication of this needs to be evaluated by follow‐up studies.     

Kangaroo Care modifies preterm infant heart rate variability in response to heel stick pain: Pilot study

Background

Heel stick is the most common painful procedure for preterm infants in neonatal intensive care units. Resultant pain causes adverse physiological effects in major organ systems. Kangaroo Care (KC), involving mother-infant skin-to-skin contact is a promising analgesic for infant pain; however, the effect of KC on the autonomic nervous system's response to pain is unknown.

Aim

To determine if KC results in improved balance in autonomic responses to heel stick pain than the standard method where infants remain in an incubator care (IC) for the heel stick.

Study design

A randomized cross-over trial.

Subjects

Fourteen preterm infants, 30-32 weeks gestational age and less than 9 days postnatal age.

Outcome measures

Infant behavioral state, heart rate, heart rate variability (HRV) indices including low frequency (LF) and high frequency (HF) power, and the LF/HF ratio measured over Baseline, Heel Warming, Heel Stick, and Recovery periods in KC and IC conditions.

Results

HRV differences between KC and IC were that LF was higher in KC at Baseline (p < .01) and at Heel Stick (p < .001), and HF was higher in KC at Baseline than in the IC condition (p < .05). The LF/HF ratio had less fluctuation across the periods in KC than in IC condition and was significantly lower during Recovery in KC than in IC (p < .001).

Conclusions

Infants experienced better balance in response in KC than IC condition as shown by more autonomic stability during heel stick. KC may be helpful in mediating physiologic response to painful procedures in preterm infants.     

川崎病患儿心率变异性与冠状动脉损害的相关性研究

目的 探讨川崎病(KD)患儿的心率变异性(HRV)指标与肌钙蛋白I(cTnI)和氨基末端脑钠肽前体(NT-proBNP)的相关性及其在预后中的应用价值。方法 将130 例KD 患儿分为冠状动脉损害组(n=47, CAL 组)和无CAL 组(n=83, NCAL 组), 同期选取110 例健康儿童为对照组, 29 例非心血管疾病恢复期患儿为非KD 组。各组儿童均行长程HRV 指标检测及分析。检测KD 组及非KD 组患儿血清NT-proBNP 及cTnI 水平。结果 同年龄性别KD 组患儿正常窦性N-N 间期标准差(SDNN)、相邻N-N 间期标准差的平均值(SDNNindex)、相邻N-N 间期之差>50 ms 的心搏数占心搏总数的百分数(PNN50)、极低频功率(VLF)、低频功率(LF)和高频功率(HF)值较对照组均明显下降, LF/HF 值较对照组升高(P<0.05)。CAL 组SDNN、全部记录中每5 min N-N 间期平均值的标准差(SDANN)、SDNNindex、相邻N-N 间期差值的均方根值(rMSSD)、PNN50、VLF、LF 和HF 值均低于对照组和非KD 组, LF/HF 值高于对照组(P<0.05)。CAL 组及NCAL 组的cTnI 和NT-proBNP 水平均高于非KD 组(P<0.05)。KD 患儿cTnI 与SDNN、HF 呈负相关, 与LF/HF 呈正相关(P<0.05);NT-proBNP 与SDNN、SDANN、HF 呈负相关(P<0.05)。结论 HRV 指标对KD 患儿的CAL 判断具有一定的临床意义。     

Nicotine in breast milk influences heart rate variability in the infant

AIM: To study the effects of postnatal exposure to nicotine on the regulation of heart rate and blood pressure in infants. SUBJECTS AND METHODS: Thirty-eight mother-infant pairs were studied. Twenty nonsmoking and 18 smoking (2-20 cigarettes per day) mothers were included. All infants were healthy, exclusively breastfed and their postnatal age was 6 weeks. During a home visit infant's urine and mothers' milk were sampled and concentrations of nicotine and cotinine were analyzed. Infants' electrocardiogram (ECG) were recorded, sleep state documented and blood pressure during sleep was measured. Heart rate variability (HRV) was calculated with spectral analysis of R-R intervals. RESULTS: The smoking mothers exposed their infants to nicotine in milk with a median nicotine concentration of 47 (8-192) mug/L. Analysis of infants' urine showed that the nonsmoking group had 0.8 (0-5.2) and the smoke group 60 (17-139) mug cotinine/L (p < 0.01). The frequency domain low-to-high frequency (LF/HF) ratio, was correlated to milk nicotine concentrations in the milk sample, from smoking mothers. HRV decreased, with increasing milk nicotine, ingested by the boys (r =-0.74, p = 0.02) but not the girls (r =-0.13, p = 0.76). The differences of mean arterial pressure between sleep states in the infants, were significantly lower in the smoke group 5.8(6.8) compared to the nonsmoke group 11.5(7.2) mmHg (p = 0.03). CONCLUSIONS: Postnatal exposure to nicotine influences autonomic cardiovascular control in infants.     

Aerobic exercise during pregnancy influences infant heart rate variability at one month of age

Background

Previously, we reported that regular maternal aerobic exercise during pregnancy was associated with lower fetal heart rate (HR) and higher heart rate variability (HRV) at 36 weeks gestation. We now report the effect of maternal exercise on infant HR and HRV in subjects who remained active in the study at the one-month follow up visit.

Aims

We aimed to determine whether differences in fetal cardiac autonomic control related to maternal physical activity were an in utero phenomenon or would persist 1 month after birth.

Study design

Magnetocardiograms (MCGs) of infants born to regularly exercising (≥ 30 min of aerobic activity, 3 times per week; N = 16) and non-exercising (N = 27) pregnant women were recorded using a fetal biomagnetometer. Normal R-peaks were marked to derive infant HR and HRV in time and frequency domains, including the root mean square of successive differences (RMSSD), the standard deviation of normal-to-normal interbeat intervals (SDNN), and power in the low frequency (LF) and high frequency (HF) bands. Group differences were examined with Student's t-tests.

Results

Infants born to exercising women had significantly higher RMSSD (P = 0.010), LF power (P = 0.002), and HF power (P = 0.004) than those born to women who did not engage in regular physical activity while pregnant.

Conclusion

Infants born to women who participated in regular physical activity during pregnancy continued to have higher HRV in the infant period. This suggests that the developing cardiac autonomic nervous system is sensitive to the effects of maternal physical activity and is a target for fetal programming.     

Night sleep heart rate patterns recorded by cardioneumography at home in normal and at-risk for SIDS infants

It has been reported that infants at higher than normal epidemiological risk for the sudden infant death syndrome (SIDS) have abnormal cardiac autonomic activity. A prospective work was performed using cardiopneumographic recordings (CPG) in order to evaluate heart rate (HR) and heart rate variability (HRV) patterns in sleeping normal control infants (C) and in infants at-risk for SIDS in their normal environment at home. One hundred appropriate-for-gestational age full-term infants were studied: 28 C, 48 SIDS siblings (SS), and 24 near-miss for SIDS (NM) within the first 2 weeks following the first detected apparent life-threatening event. The three groups of infants were comparable with respect to gestational and conceptional ages, birthweights, sex distribution and socio-economic backgrounds. CPG were done over two successive nights. Records were visually analysed for sleep states (quiet: QS, and combined active + indeterminate sleep: AIS) and wakefulness (W) coding. Periods of W were not analysed. An automatic programme allowed us to study HR minute-by-minute, and to assess whether HR and HRV patterns were specific to a certain part of the night, records were divided into three periods (2200—0040 h, 0041—0320 h, and 0321—0600 h). In C and SS groups, the HR was significantly lower in the 2nd night-period than in the 1st and 3rd periods in both QS and AIS (P < 0.05). In the NM group this difference was only observed during AIS (P < 0.05). During the three night-periods the HR was significantly elevated in AIS as compared to QS (at least (P < 0.05) in all infant groups except the NM group during the 2nd night-period. During QS the HR was significantly higher in NM than in C and SS groups (P < 0.02). During AIS the HR did not differ between infant groups. HRV was significantly lower in the NM group during QS in the three night-periods (P < 0.05). There was no difference in the HR and HRV patterns between C and SS groups with respect to sleep states and night period. We concluded that following the first detected apparent life-threatening event differences in the HR and HRV patterns can be demonstrated when sleeping NM infants are compared with both C and SS infants especially during QS in different night periods studied by CPG at home.