Heart rate and heart rhythm in healthy infants and children

Cardiac rate and rhythm in 141 healthy infants, toddlers and schoolchildren during 24 hour ambulatory electrocardiographic monitoring are reported. Maximal and minimal heart rate (1/min) in infants 1 to 5 months of age were 204 +/- 17 and 105 +/- 13, in infants 6 to 12 months of age 187 +/- 19 and 101 +/- 15; in toddlers 177 +/- 17 and 66 +/- 10; in schoolchildren 158 +/- 24 and 54 +/- 6. A sizeable proportion of children of all age groups showed patterns of sinus arrhythmias indistinguishable from second degree sinuatrial block. Supraventricular escape beats and escape rhythms were frequent as well. The longest RR interval was 1.03 +/- 0.16 sec. in infants, 1.20 +/- 0.25 sec. in toddlers, and 1.35 +/- 0.15 sec., respectively, in schoolchildren. Two % of infants, 7% of toddlers, and 6% of schoolchildren had episodes of second degree atrioventricular block type I (Wenckebach) at rest. Supraventricular extrasystoles were found in 38%, 13% and 26%, respectively, and uniform ventricular extrasystoles in 18%, 20% and 16%, respectively, of infants, toddlers and schoolchildren. These data, together with similar information in the literature, can be taken as basis for the evaluation of ambulatory electrocardiograms in children.     

Heart rate and oxygen uptake response to exercise in children with low peak exercise heart rate

Normal children achieve the same increase of oxygen uptake (VO₂) in response to exercise even though resting and submaximal exercise heart rates vary greatly as a function of age, body size and physical conditioning. To determine whether the VO₂ response to exercise is altered when heart rate is significantly reduced by heart disease, we compared 78 children who achieved a peak exercise heart rate of 150 beats/min to 201 controls of similar body size and normal peak exercise heart rates of 180 beats/min. All performed incremental (16.4 Watts/min) maximal cycle exercise. Separate analysis of males and females included heart rate, power (kg-m/min, Watts/kg), VO₂ (ml/min, ml/min per kg), O₂ pulse (VO₂/heart beat), V_E (l/min) and R (VCO₂/VO₂) at rest and during the 1st, 4th and last minute of exercise. Patients with low peak exercise heart rates had also lower resting submaximal exercise heart rates than controls. VO₂ at comparable exercise levels did not differ from controls and consequently O₂ pulse was greater in the patients than controls at rest and at all levels of exercise. A consistent gender difference was only found in controls where males achieved a higher VO₂ and lower heart rates at comparable levels of exercise. The data show a normal exercise VO₂ despite significantly lower heart rates. These findings cannot be explained by an increased arteriovenous difference alone and suggest that the patients retained the ability to effectively modulate stroke volume.     

正常儿童动态心电图窦性心率及心率变异分析

目的探讨正常儿童心率及心率变异性(HRV)特点。方法对804例正常儿童进行24h全程动态心电图检查,分析心率及HRV。结果不同年龄儿童窦性心率范围不同,年龄越小心率越快;儿童不同性别间HRV中24h内全部正常心动周期的标准差(SDNN)、24h内每5minNN间期标准差的平均值(SDNNindex)、NN50占所有N-N间期个数的百分数(PNN50)、极低频率(VLF)、低频(LF)差异有显著性;儿童不同年龄组间24h内5min节段平均心动周期的标准差(SDANN)、VLF、LF、全程相邻NN间期之间的均方根值(rMSSD)差异有显著性;儿童组与成人正常参考值中SDNN、SDANN、rMSSD差异有显著性,rMSSD儿童组中明显高于成人组。结论HRV是一种反映自主神经活性及其平衡的能定量、可重复的非侵入性的检测方法,是自主神经系统与心血管系统相互制约的结果。不同年龄、不同性别间儿童HRV存在显著差异;儿童组与成人参考值存在显著差异,尤其rMSSD儿童明显高于成人,提示儿童的自主神经功能较成人活跃,而随着年龄增长自主神经功能减退,尤其是迷走神经的紧张抑制功能明显减退。     

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.     

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 and reinforcement sensitivity in ADHD

BACKGROUND: Both theoretical and clinical accounts of attention-deficit/hyperactivity disorder (ADHD) implicate a dysfunctional reinforcement system. This study investigated heart rate parameters in response to feedback associated with reward and response cost in ADHD children and controls aged 8 to 12. METHODS: Heart rate responses (HRRs) following feedback and heart rate variability (HRV) in the low frequency band (.04-.08 Hz), a measure of mental effort, were calculated during a time production paradigm. Performance was coupled to monetary gain, loss or feedback-only in a cross-over design. RESULTS: Children with ADHD exhibited smaller HRRs to feedback compared to controls. HRV of children with ADHD decreased when performance was coupled to reward or response cost compared to feedback-only. HRV of controls was similar across conditions. CONCLUSIONS: Children with ADHD were characterised by (a) possible abnormalities in feedback monitoring and (b) motivational deficits, when no external reinforcement is present.     

Does fetal heart rate predict subsequent heart rate in childhood?

An investigation to determine whether there is any relationship between extremes of fetal heart rate during labour and subsequent heart rate at the age of 10 was carried out using data from the 1970 cohort of British Births. In 11,000 nationally representative children it was found that low fetal heart rate (below 120 beats/min) was associated with a heart rate at age 10 which was significantly lower than in those children whose fetal heart rate had remained between 120 and 160 beats/min (P less than 0.01). This relationship could not be explained by fetal asphyxiation, maternal antenatal hypotension or the method of pain relief during labour. There was no equivalent relationship with high fetal heart rate during labour. This could imply that some fetuses with low heart rates are not exhibiting fetal distress but have an inherent tendency to relatively slow heart rates.     

正常新生儿心率变异性研究

目的 探讨正常新生儿心率变异性（HRV）的特点。方法 应用Compas XM Holter分析系统对35例正常足月新生儿进行HRV时域分析。结果 新生儿出生后1～7d与8～28d HRV指标无差异（P＞0.05）。24h正常RR间期标准差（SDNN）、心率变异性指数（HRVI）与24h平均心率（AHR）、最慢心率（MiHR）呈中度负相关（r值分别为-0.44,-0.43,-0.51,-0.56,P﹤.05）。结论 HRV是反映新生儿心脏自主神经功能较稳定的指标,结果可供新生儿HRV研究参考。     

心肌炎患儿与正常儿童心率及心率变异性比较分析

目的 研究不同年龄心肌炎患儿的心率及心率变异性(HRV)改变的特点和相关性.方法 对120例心肌炎患儿进行24 h全程动态心电图检查,与804例正常儿童的心率及HRV进行比较分析.结果 7岁以下患儿最慢心率较正常增快,最快心率比较变化无差异,7～18岁患儿心率监测指标均异常;3～7岁心肌炎患儿与正常儿童比较每5分钟R-R间期平均值的标准差(SDANN)无变化,各组其他HRV指标均降低.结论 心肌炎患儿的HRV普遍降低,提示心脏自主神经系统的总体功能受损,以迷走神经张力降低为主,交感神经张力相对增强.     

Heart and heart–lung transplant

Heart transplantation not only enables children with end-stage heart failure to live longer, but also improves their quality of life. Peritransplant survival has improved with advances in intensive care and better mechanical support systems for the failing heart. Heart–lung transplantation is the only option for some children near the end of life from disease affecting both organs and remains a challenge, with much poorer outcomes than heart transplantation alone. All thoracic transplants require scrupulous attention to follow-up care and, despite improving outcomes, can be regarded only as palliative solutions. The medical and surgical management of heart failure and congenital heart disease has also improved in recent years, and these options are thoroughly explored before considering listing for heart transplantation.     

早产儿心率变异性的临床研究

目的评价早产儿心脏自主神经功能发育情况.方法根据胎龄将90例早产儿分为A、B、C三组(胎龄分别为27～31周、～34周、～37周),以CompasXMHolter系统检测90例早产儿及21例足月儿的心率变异性时域指标.结果A、B、C三组24h窦性RR间期标准差的均值(SDNN)、每5min窦性RR间期标准差的均值(SDN-NIDX)、50ms间隔以上邻近周期的比例(PNN50)与对照组比较差异有显著性意义(P＜0.05).A组SDNNIDX与B、C组比较,差异有显著性意义(P＜0.05).SDNN与胎龄正相关(r=0.55,P＜0.01),PNN50与日龄正相关(r=0-23,P＜0.05).结论早产儿自主神经功能随胎龄增大逐渐成熟.胎龄大于34周早产儿交感神经功能接近足月儿.大于34周龄早产儿交感神经功能较稳定,副交感神经功能随日龄增加而增强.     

Analysts on heart rate variability and deceleration capacity of heart rate in preschoolers with viral myocarditis

目的 探讨病毒性心肌炎患儿心率变异性(HRV)与心率减速力(DC)各项指标变化的临床意义.方法 对56例病毒性心肌炎患儿与58例正常对照儿童进行24h动态心电图检查,应用美国DMS公司的动态心电分析系统软件,对HRV及DC各项参数进行分析对比;并分析DC与其他各项指标之间的相关性.结果 与正常对照儿童比较,病毒性心肌炎患儿时域分析的各项参数包括正常窦性RR间期的标准差(SDNN)、每5 min时段内平均正常窦性RR间期的标准差(SDANN)、全程RR间期差的均方根(RMSSD)及频域分析的低频功率(LF)的差异均无统计学意义(P＞0.05),而高频功率(HF)显著减低,差异有统计学意义(P＜0.05),且DC显著减低,差异有统计学意义(P＜0.01).相关性分析中,DC与SDNN、LF、HF均成正相关,其中与HF的相关性最强(r=0.51,P＜0.01).结论病毒性心肌炎患儿存在迷走神经功能受损,心率变异性中的HF与DC反映迷走神经功能的指标均显著降低,且两者具有很大相关性.     

学龄期肥胖儿童胰岛素抵抗与心率变异性及心率减速力的相关性

目的探讨学龄期肥胖儿童胰岛素抵抗(IR)与心率变异性(HRV)、心率减速力(DC)及心率加速力(AC)之间的关系。方法选取学龄期6～10岁肥胖儿童83例,根据空腹血糖及空腹胰岛素值计算胰岛素抵抗指数(IRI),再根据IRI值将实验对象分为IR组45例和非IR组38例。在检测空腹血糖及空腹胰岛素同日行24小时动态心电图检查,计算出DC、AC、HRV各指标。比较IR组与非IR组DC、AC、HRV各指标,并进行相关性分析。结果 IR组DC、正常RR间期标准差(SDNN)、5分钟均值标准差(SDANN)、高频功率(HF)均低于非IR组,AC高于非IR组,差异均有统计学意义(P0.05)。肥胖儿童的IRI与DC、SDNN、SDANN、相邻RR间期差值的均方根(RMSSD)、低频功率(LF)、HF均呈显著负相关(r=-0.475～-0.249,P0.05),与AC呈显著正相关(r=0.488,P0.01)。结论 IR较非IR肥胖儿童的自主神经功能损伤严重,主要表现为迷走神经张力降低,且IRI越高,迷走神经张力越低。     

Heart rate features in fetal behavioural states

Background and aim

Fetal behavioural states have been defined on the basis of eye movements, body movements and heart rate patterns as presented by cardiotocography (CTG). The aim of this work was to determine whether behavioural states can be distinguished on the basis of heart rate features alone using high resolution beat-to-beat fetal magnetocardiography.

Study design

Five minute magnetocardiograms were recorded at a sampling rate of 1 kHz in 40 healthy fetuses (36th-41st week of gestation). In the reconstructed RR interval time series, 256-beat epochs corresponding to the behavioural states 1F, 2F and 4F were visually identified according to heart rate patterns as defined for CTG. These epochs were then quantified using mean RR interval, its standard deviation (SDNN), its root mean square of successive difference (RMSSD) and on the basis of symbolic dynamics of short 8 beat trains.

Results

Pairwise comparison between the behavioural states showed that the values of each of these measures differed significantly between the states. Quadratic discriminant analysis further revealed that mean RR interval and SDNN sufficed to classify state with a correct classification of 92%.

Conclusions

The results suggest that measures that quantify overall aspects of heart rate can distinguish RR interval time series which were classified into different fetal behavioural states. The differences in short-term variability as quantified by RMSSD and symbolic dynamics may help reveal new aspects of these states.     

学龄前儿童病毒性心肌炎心率变异性与心率减速力分析

目的探讨病毒性心肌炎患儿心率变异性(HRV)与心率减速力(DC)各项指标变化的临床意义。方法对56例病毒性心肌炎患儿与58例正常对照儿童进行24 h动态心电图检查,应用美国DMS公司的动态心电分析系统软件,对HRV及DC各项参数进行分析对比;并分析DC与其他各项指标之间的相关性。结果与正常对照儿童比较,病毒性心肌炎患儿时域分析的各项参数包括正常窦性RR间期的标准差(SDNN)、每5 min时段内平均正常窦性RR间期的标准差(SDANN)、全程RR间期差的均方根(RMSSD)及频域分析的低频功率(LF)的差异均无统计学意义(P>0.05),而高频功率(HF)显著减低,差异有统计学意义(P<0.05),且DC显著减低,差异有统计学意义(P<0.01)。相关性分析中,DC与SDNN、LF、HF均成正相关,其中与HF的相关性最强(r=0.51,P<0.01)。结论病毒性心肌炎患儿存在迷走神经功能受损,心率变异性中的HF与DC反映迷走神经功能的指标均显著降低,且两者具有很大相关性。     

Pressure-volume relationships in pediatric systolic and diastolic heart failure

The left ventricular pressure-volume relationship has been used to examine ventricular systolic and diastolic function as well as to evaluate myocardial energetics and ventricular-vascular coupling. Preload, afterload and contractility can be separately examined using indices derived from simultaneous pressure and volume measurement. Due to the development of new instrumentation and diagnostic tools, these techniques now can be more readily applied to the evaluation of patients in heart failure. Indices of function can be examined on-line during diagnostic cardiac catheterization. Pharmacologic interventions can be evaluated using these methods, allowing for assessment of therapeutic interventions. Medical therapy can be optimized during these studies, allowing more effective and individualized treatment.