Maturation of heart rate and blood pressure variability during sleep in term-born infants

Impact of Kangaroo mother care on autonomic cardiovascular control in foetal-growth-restricted preterm infants

BACKGROUND

Kangaroo mother care (KMC) is WHO-recommended for low-birth-weight infants, yet its impact on autonomic cardiovascular control in preterm foetal growth-restricted (FGR) infants remains unclear. We hypothesised that KMC would promote autonomic cardiovascular control, benefiting preterm FGR infants with reduced baseline autonomic function compared to appropriate for gestational age (AGA) infants.

METHODS

Autonomic control was assessed via heart rate variability (HRV) in low frequency (LF) and high frequency (HF) bands using spectral analysis. Preterm FGR (n = 22) and AGA (n = 20) infants were assessed for 30-min before and 60-min during KMC. Comparisons were made between FGR and AGA infants; and between infants with baseline HRV below and above median.

RESULTS

Overall, no significant HRV changes were observed during KMC for FGR or AGA infants compared to baselines. Infants with low baseline HRV LF showed increased HRV during KMC (p = 0.02 and 0.05 for the entire group and FGR group, respectively). This effect was absent in the AGA group regardless of baseline HRV. Infants with high baseline HRV had decreased HRV during KMC.

CONCLUSIONS

Infants with low baseline HRV, suggesting reduced autonomic control, are more likely to benefit from KMC with increased HRV. Further, this effect is stronger in FGR than AGA infants.

IMPACT

Kangaroo mother care (KMC) is WHO-recommended for low-birth-weight infants, yet its impact on autonomic cardiovascular control in preterm foetal growth-restricted (FGR) infants is unclear. Preterm infants with low baseline heart rate variability (HRV) are more likely to benefit from KMC and increase their HRV suggesting improved autonomic control. This effect is stronger in preterm FGR infants than those with appropriate growth for age.

Characterising the motion and cardiorespiratory interaction of preterm infants can improve the classification of their sleep state

AIM

This study aimed to classify quiet sleep, active sleep and wake states in preterm infants by analysing cardiorespiratory signals obtained from routine patient monitors.

METHODS

We studied eight preterm infants, with an average postmenstrual age of 32.3 ± 2.4 weeks, in a neonatal intensive care unit in the Netherlands. Electrocardiography and chest impedance respiratory signals were recorded. After filtering and R-peak detection, cardiorespiratory features and motion and cardiorespiratory interaction features were extracted, based on previous research. An extremely randomised trees algorithm was used for classification and performance was evaluated using leave-one-patient-out cross-validation and Cohen's kappa coefficient.

RESULTS

A sleep expert annotated 4731 30-second epochs (39.4 h) and active sleep, quiet sleep and wake accounted for 73.3%, 12.6% and 14.1% respectively. Using all features, and the extremely randomised trees algorithm, the binary discrimination between active and quiet sleep was better than between other states. Incorporating motion and cardiorespiratory interaction features improved the classification of all sleep states (kappa 0.38 ± 0.09) than analyses without these features (kappa 0.31 ± 0.11).

CONCLUSION

Cardiorespiratory interactions contributed to detecting quiet sleep and motion features contributed to detecting wake states. This combination improved the automated classifications of sleep states.

Methods for analyzing infant heart rate variability: A preliminary study

Heart rate (HR) and heart rate variability (HRV) reflect autonomic development in infants. To better understand the autonomic response in infants, reliable HRV recordings are vital, yet no protocol exists. The purpose of this paper is to present reliability of a common procedure for analysis from two different file types. In the procedure, continuous electrocardiograph recordings of 5-10 min are obtained at rest in infants at 1 month of age by using a Hexoskin Shirt-Junior's (Carre Technologies Inc., Montreal, QC, Canada). Electrocardiograph (ECG; .wav) and R-R interval (RRi; .csv) files are extracted. The RRi of the ECG signal is generated by VivoSense (Great Lakes NeuroTechnologies, Independence, OH). Two MATLAB (The MathWorks, Inc., Natick, MA) scripts converted files for analysis with Kubios HRV Premium (Kubios Oy, Kuopio, Finland). A comparison was made between RRi and ECG files for HR and HRV parameters, and then tested with t tests and correlations via SPSS. There are significant differences in root mean squared successive differences between recording types, with only HR and low-frequency measures significantly correlated together. Recording with Hexoskin and analysis with MATLAB and Kubios enable infant HRV analysis. Differences in outcomes exist between procedures, and standard methodology for infant HR analysis is needed.

Dynamic touch induces autonomic changes in preterm infants as measured by changes in heart rate variability

Preterm birth significantly increases the risk of developing various long-term health problems and developmental disabilities. While touch is a crucial component of many perinatal care strategies, the neurobiological underpinnings are rarely considered. C-tactile fibers (CTs) are unmyelinated nerve fibers that are activated by low-force, dynamic touch. Touch directed specifically at CTs activates the posterior insular cortex, consistent with an interoceptive function, and has been shown to reduce heart rate and increase oxygen saturation. The current research compared the effect of five minutes of CT optimal velocity stroking touch versus five minutes of static touch on autonomic markers of preterm infants between 28 and 37 weeks gestational age. CT touch induces a higher increase in heart rate variability metrics related to the parasympathetic system, which persisted for a 5-minute post-touch period. Conversely, there was no such increase in infants receiving static touch. The present findings confirmed that CTs signal the affective quality of nurturing touch, thereby arguing an additional neurobiological substrate for the evident valuable impacts of neonatal tactile interventions and improving the effectiveness of such interventions.

When the Mind Comes to Live Inside the Body: The Ontogeny of the Perceptual Control Clock

In this editorial, we discuss the neurobiological processes underlying the early emergence of awareness that we term the "when" and "how" the mind comes to live inside the body. We describe an accumulative developmental process starting during embryonic life and continuing to fetal and postnatal development, of coupling of heart rate, body movements, and sleep states on the behavioral level with underlying mechanisms on the structural, functional, cellular, and molecular levels. A developmental perspective is proposed based on Perceptual Control Theory (PCT). This includes a developing sequence of modules starting from early sensing of neural intensities to early manifestation of human mindful capacities. We also address pharmacological treatments administered to preterm infants, which may interfere with this development, and highlight the need to consider this potential "side effect" of current pharmaceuticals when developing novel pharmacogenomic treatments.

Using Temporal Data Mining on Patient Data for Clinical Decision Making in the Care of the Sick Newborn

BACKGROUND

In a neonatal intensive care unit, streaming healthcare data comes from many sources, but humans are unable to understand relationships between data variables. Data mining and analysis are just beginning to get utilized in critical care. We present a case study using electronic medical record data in the neonatal intensive care unit and explore possible avenues of advancement using temporal data analytics.

CASE PRESENTATION

Electronic medical record data were collected for physiological monitor data. Heart rate, respiratory rate, oxygen saturation and temperature data were retrospectively analyzed by temporal data mining. Three premature babies were selected and data de-identified. The first case of a urinary tract infection showed nursing ability to synthesize data streams coming from a patient. For the second case of necrotizing enterocolitis, Temporal-Data-Mining analysis of combinations of clinical events based on deviations from the mean showed specific heuristic biomarkers related to events before discovery of necrotizing enterocolitis. Specific sequences 6-event and 5-event in length were identified with nursing unease at clinical deterioration, which were 100- and 87-times unlikely to occur randomly with 99.5% confidence. No such sequences were found in the rest of the 37 days for the second case and entire 133 days of stay in the third case of an uneventful premature baby.

CONCLUSION

Temporal data mining is a possible clinical tool in providing useful information in the neonatal intensive care unit for diagnosis of adverse clinical occurrences such as necrotizing enterocolitis. There is the possibility of changing the clinical paradigm of episodic watchfulness to constant vigilance using real-time data gathering.

Osteopathic Manipulative Treatment Regulates Autonomic Markers in Preterm Infants: A Randomized Clinical Trial

Osteopathic manipulative treatment (OMT) has been found to be effective in the context of premature infants. Nonetheless, no studies have investigated the immediate effects of OMT on heart rate variability (HRV). As altered HRV reflects poor or worsening newborn's clinical conditions and neurodevelopment, should OMT improve HRV fluctuations, it could become a relevant intervention for improving the care of preterm newborns. Therefore, this study aimed to evaluate whether OMT could affect HRV. The study was carried out at the Buzzi Hospital in Milan. From the neonatal intensive care unit, ninety-six preterm infants (41 males) were enrolled and were randomly assigned to one of two treatment groups: OMT or Static Touch. The infants were born at 33.5 weeks (±4.3) and had a mean birth weight of 2067 g (±929). The study had as primary outcome the change in the beat-to-beat variance in heart rate measured through root mean square of consecutive RR interval differences (RMSSD); other metrics were used as secondary and exploratory analyses. Despite the lack of statistically significant results regarding the primary outcomeand some study limitations, compared to static touch, OMT seemed to favor a parasympathetic modulation and improved HRV, which could reflect improvement in newborn's clinical conditions and development.

A Review on the Vagus Nerve and Autonomic Nervous System During Fetal Development: Searching for Critical Windows

The autonomic nervous system (ANS) is one of the main biological systems that regulates the body's physiology. Autonomic nervous system regulatory capacity begins before birth as the sympathetic and parasympathetic activity contributes significantly to the fetus' development. In particular, several studies have shown how vagus nerve is involved in many vital processes during fetal, perinatal, and postnatal life: from the regulation of inflammation through the anti-inflammatory cholinergic pathway, which may affect the functioning of each organ, to the production of hormones involved in bioenergetic metabolism. In addition, the vagus nerve has been recognized as the primary afferent pathway capable of transmitting information to the brain from every organ of the body. Therefore, this hypothesis paper aims to review the development of ANS during fetal and perinatal life, focusing particularly on the vagus nerve, to identify possible "critical windows" that could impact its maturation. These "critical windows" could help clinicians know when to monitor fetuses to effectively assess the developmental status of both ANS and specifically the vagus nerve. In addition, this paper will focus on which factors-i.e., fetal characteristics and behaviors, maternal lifestyle and pathologies, placental health and dysfunction, labor, incubator conditions, and drug exposure-may have an impact on the development of the vagus during the above-mentioned "critical window" and how. This analysis could help clinicians and stakeholders define precise guidelines for improving the management of fetuses and newborns, particularly to reduce the potential adverse environmental impacts on ANS development that may lead to persistent long-term consequences. Since the development of ANS and the vagus influence have been shown to be reflected in cardiac variability, this paper will rely in particular on studies using fetal heart rate variability (fHRV) to monitor the continued growth and health of both animal and human fetuses. In fact, fHRV is a non-invasive marker whose changes have been associated with ANS development, vagal modulation, systemic and neurological inflammatory reactions, and even fetal distress during labor.

Physiological vital sign reference ranges for well late preterm newborns calculated during a typical two-hour newborn period between 2 hours and 7 days of life

Objectives To calculate 95% reference ranges for heart rate, respiratory rate, oxygen saturation, temperature and blood pressure for well late preterm newborns between 34+0/7 and 36+6/7 weeks of gestation during typical neonatal behaviour. Approach A single site, prospective cohort study in a major Australian quaternary hospital between February and September 2019. A total of 120 late preterm newborns had their heart rate, respiratory rate and oxygen saturation measurements recorded every two seconds for up to two hours with unconditional 95% reference ranges determined using a linear mixed model with random intercept for total standard deviation calculation including repeated measures. Temperature and blood pressure measurements were collected twice - at the start and conclusion of the data recording period, with weighted 2.5th and 97.5th percentiles calculated using the mean value. Main results A total of 364,577 heart rate, 365,208 respiratory rate, 360,494 peripheral oxygen saturation, and 240 temperature and blood pressure values were obtained. The 95% reference ranges were: heart rate 102 - 164 bpm; respiratory rate 15 - 67 rpm; oxygen saturation 94 - 100%; temperature 36.4 - 37.6°C; systolic blood pressure 51 - 86 mmHg; diastolic blood pressure 28 - 61 mmHg; mean arterial pressure 35 - 68 mmHg. Significance Seven vital sign references ranges were reported for the late preterm population during a typical newborn period (such as crying, sleeping, feeding, awake and alert, and during nappy hygiene cares); internal and external validation should be completed prior to clinical use. Cut off points for escalation of care have previously been generalised to all newborns irrespective of gestational age which may result in over-treatment or a delay in recognising subtle signs of deterioration.

Contribution of K2P Potassium Channels to Cardiac Physiology and Pathophysiology

Years before the first two-pore domain potassium channel (K2P) was cloned, certain ion channels had already been demonstrated to be present in the heart with characteristics and properties usually attributed to the TREK channels (a subfamily of K2P channels). K2P channels were later detected in cardiac tissue by RT-PCR, although the distribution of the different K2P subfamilies in the heart seems to depend on the species analyzed. In order to collect relevant information in this regard, we focus here on the TWIK, TASK and TREK cardiac channels, their putative roles in cardiac physiology and their implication in coronary pathologies. Most of the RNA expression data and electrophysiological recordings available to date support the presence of these different K2P subfamilies in distinct cardiac cells. Likewise, we show how these channels may be involved in certain pathologies, such as atrial fibrillation, long QT syndrome and Brugada syndrome.

Heart rate variability in Dorper sheep in the fetal and neonatal periods until 120 days of age: Use of the technique in the field

The evaluation of the autonomic cardiac functions may be performed through the analysis of the heart rate variability. Heart rate variability is defined as the fluctuations in the heart rhythm or rate, and represents a useful tool in the evaluation of the autonomic nervous system through the sympathetic and parasympathetic components, as well as its balance and its reflexes on the cardiorespiratory control system. Fetal electrocardiography provides important information regarding the well-being of the fetus since, in human fetuses, there are changes in the behavior of the fetal heart rate during the second and third trimesters of pregnancy due to an increase in parasympathetic activity. Therefore, considering the importance of evaluating fetal viability, this study aims at evaluating the behavior of fetal heart rate and heart rate variability in Dorper sheep, as well as the activity of the autonomic nervous system during fetal life and in newborn lambs. The species is often used in experimental studies and autonomic nervous system activity is a prognostic index, therefore, the diagnosis of modifications in the sympathovagal balance may represent an early index for fetal viability and well-being in lambs. The analyses were performed in 10 Dorper sheep during pregnancy and in 10 lambs after birth until 120 days of age. There was a decrease in the fetal heart rate and heart rate variability indexes during the fifth month of pregnancy, but without statistical significance for the period evaluated. The heart rate of the lambs decreased gradually until they were 21 days old. The indexes SDNN (standard deviation of RR intervals) and RMSSD (square root of the mean of successive differences between adjacent RR intervals) diverged according to age, being high at day 60. Fetal viability is relevant in sheep fetuses to avoid losses during pregnancy and risks to the health of the mother. In the species, there seems to be a predominance of parasympathetic activity starting from the 21st day of age. Heart rate variability may be employed as a tool in the evaluation of the fetus and development of lambs, since changes in its behavior may represent an adverse effect to fetal and neonatal health.

Severe neurological outcomes after very early bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD)

To test the association between bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD) and long-term clinical outcome and to identify risk factors for severe outcomes, a dataset comprising 504 patients from the international registry study ARegPKD was analyzed for characteristics and complications of patients with very early (≤ 3 months; VEBNE) and early (4–15 months; EBNE) bilateral nephrectomies. Patients with very early dialysis (VED, onset ≤ 3 months) without bilateral nephrectomies and patients with total kidney volumes (TKV) comparable to VEBNE infants served as additional control groups. We identified 19 children with VEBNE, 9 with EBNE, 12 with VED and 11 in the TKV control group. VEBNE patients suffered more frequently from severe neurological complications in comparison to all control patients. Very early bilateral nephrectomies and documentation of severe hypotensive episodes were independent risk factors for severe neurological complications. Bilateral nephrectomies within the first 3 months of life are associated with a risk of severe neurological complications later in life. Our data support a very cautious indication of very early bilateral nephrectomies in ARPKD, especially in patients with residual kidney function, and emphasize the importance of avoiding severe hypotensive episodes in this at-risk cohort.

Heart Rate Variability in the Perinatal Period: A Critical and Conceptual Review

Neonatal intensive care units (NICUs) greatly expand the use of technology. There is a need to accurately diagnose discomfort, pain, and complications, such as sepsis, mainly before they occur. While specific treatments are possible, they are often time-consuming, invasive, or painful, with detrimental effects for the development of the infant. In the last 40 years, heart rate variability (HRV) has emerged as a non-invasive measurement to monitor newborns and infants, but it still is underused. Hence, the present paper aims to review the utility of HRV in neonatology and the instruments available to assess it, showing how HRV could be an innovative tool in the years to come. When continuously monitored, HRV could help assess the baby’s overall wellbeing and neurological development to detect stress-/pain-related behaviors or pathological conditions, such as respiratory distress syndrome and hyperbilirubinemia, to address when to perform procedures to reduce the baby’s stress/pain and interventions, such as therapeutic hypothermia, and to avoid severe complications, such as sepsis and necrotizing enterocolitis, thus reducing mortality. Based on literature and previous experiences, the first step to efficiently introduce HRV in the NICUs could consist in a monitoring system that uses photoplethysmography, which is low-cost and non-invasive, and displays one or a few metrics with good clinical utility. However, to fully harness HRV clinical potential and to greatly improve neonatal care, the monitoring systems will have to rely on modern bioinformatics (machine learning and artificial intelligence algorithms), which could easily integrate infant’s HRV metrics, vital signs, and especially past history, thus elaborating models capable to efficiently monitor and predict the infant’s clinical conditions. For this reason, hospitals and institutions will have to establish tight collaborations between the obstetric, neonatal, and pediatric departments: this way, healthcare would truly improve in every stage of the perinatal period (from conception to the first years of life), since information about patients’ health would flow freely among different professionals, and high-quality research could be performed integrating the data recorded in those departments.

Human pluripotent stem cell-derived cardiomyocytes for studying energy metabolism

Cardiomyocyte energy metabolism is altered in heart failure, and primary defects of metabolic pathways can cause heart failure. Studying cardiac energetics in rodent models has principal shortcomings, raising the question to which extent human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM) can provide an alternative. As metabolic maturation of CM occurs mostly after birth during developmental hypertrophy, the immaturity of hiPSC-CM is an important limitation. Here we shortly review the physiological drivers of metabolic maturation and concentrate on methods to mature hiPSC-CM with the goal to benchmark the metabolic state of hiPSC-CM against in vivo data and to see how far known abnormalities in inherited metabolic disorders can be modeled in hiPSC-CM. The current data indicate that hiPSC-CM, despite their immature, approximately mid-fetal state of energy metabolism, faithfully recapitulate some basic metabolic disease mechanisms. Efforts to improve their metabolic maturity are underway and shall improve the validity of this model.

Common Genetic Variants Link the Abnormalities in the Gut-Brain Axis in Prematurity and Autism

This review considers a link between prematurity and autism by comparing symptoms, physiological abnormalities, and behavior. It focuses on the bidirectional signaling between the microbiota and the brain, here defined as the microbiota-gut-vagus-heart-brain (MGVHB) axis and its systemic disruption accompanying altered neurodevelopment. Data derived from clinical and animal studies document increased prevalence of gastrointestinal, cardiovascular, cognitive, and behavioral symptoms in both premature and autistic children and suggest an incomplete maturation of the gut-blood barrier resulting in a “leaky gut,” dysbiosis, abnormalities in vagal regulation of the heart, altered development of specific brain regions, and behavior. Furthermore, this review posits the hypothesis that common genetic variants link the abnormalities in the MGVHB axis in premature and autistic pathologies. This hypothesis is based on the recently identified common genetic variants: early B cell factor 1 (EBF1), selenocysteine tRNA-specific eukaryotic elongation factor (EEFSEC), and angiotensin II receptor type 2 (AGTR2), in the maternal and infant DNA samples, associated with risk of preterm birth and independently implicated in a risk of autism. We predict that the AGTR2 variants involved in the brain maturation and oxytocin-arginine-vasopressin (OXT-AVP) pathways, related to social behavior, will contribute to our understanding of the link between prematurity and autism paving a way to new therapies.

Noninvasive assessment of autonomic function in human neonates born at the extremes of fetal growth spectrum

Birth weight is associated with adult cardiovascular disease, such that those at both ends of the spectrum are at increased risk. This may be driven in part by modification to autonomic control, a mechanistic contributor to hypertension. However, birth weight is a relatively crude surrogate of fetal growth; and newborn body composition may more accurately identify the "at risk" infant. Accordingly, we sought to determine whether newborns with high or low body fat have altered autonomic control of vasomotor function and cardiac contractility. Body fat was assessed by air-displacement plethysmography <24 h postnatal. Measures of spontaneous baroreflex sensitivity (sBRS), blood pressure variability (BPV), and dP/dt_max variability were compared between newborns categorized according to established body fat percentiles: high body fat (HBF, >90th percentile, n = 7), low body fat (LBF, ≤10th percentile, n = 12), and normal body fat (control, >25th to ≤75th percentile, n = 23). BPV was similar across body fat percentiles; similarly, low frequency dP/dt_max variability was similar across body fat percentiles. sBRS was reduced in HBF compared to controls (11.0 ± 6.0 vs. 20.1 ± 9.4 msec/mmHg, P = 0.03), but LBF did not differ (18.4 ± 6.0 msec/mmHg, P = 0.80). Across the entire body fat spectrum (n = 62), there was a nonlinear association between newborn body fat and sBRS (P = 0.03) that was independent of birth weight (P = 0.04). Autonomic modulation of vasomotor function and cardiac contractility in the newborn did not differ by body fat, but newborns born with high body fat show depressed baroreflex sensitivity.

Is prone sleeping dangerous for neonates? Polysomnographic characteristics and NDN gene analysis

Objective:

Prone sleep is an identified risk factor for sudden infant death syndrome, possibly due to reduced blood pressure, cerebral oxygenation, and impaired cerebral vascular control. Cardiac and respiratory responses in neonates during supine and prone sleep have not been reported.

Materials and Methods:

In this study, daytime polysomnography (PSG) data from 17 neonates aged 2–3 days during supine and prone sleep were reported and the NDN gene, an important gene for neonatal respiratory control, was sequenced for correlation with neonatal respiratory parameters. Heart rate (HR), oxygen saturation, carbon dioxide concentration, sleep stages, central apnea index (CAI), obstructive apnea/hypopnea index (OAHI), and oxygen nadir were compared between supine and prone sleep and between participants with different single-nucleotide polymorphisms (SNPs) in the NDN gene.

Results:

During prone sleep, neonates had a faster HR, decreased oxygen saturation, and a longer duration of oxygen saturation <90% than during supine sleep, suggesting that cardiopulmonary responsiveness was impaired. Sleep efficiency, sleep stages, oxygen nadir, and carbon dioxide tension were not different during supine and prone sleep. Central apnea occurred more significantly than obstructive apnea. During supine and prone sleep, the CAI was 3.3 ± 2.9/h and 2.3 ± 2.6/h and the OAHI was 0.6 ± 0.7/h and 0.6 ± 0.8/h, respectively. We found one SNP rs3743340 in the NDN gene that had no effect on the sleep and respiratory parameters of PSG.

Conclusion:

Tachycardia and respiratory instability were recorded in neonates during prone sleep, suggesting that neonates are vulnerable to cardiopulmonary events during prone sleep. Therefore, young neonates should be kept in the supine sleep position unless there are contraindications.

Autonomic Function and QT Interval During Night-Time Sleep in Infant Long QT Syndrome

BACKGROUND

Sudden infant death syndrome mainly occurs during night-time sleep. Approximately 10% of cases are thought to involve infants with long QT syndrome (LQTS). Autonomic function and QT interval in night-time sleep in early infancy in LQTS infants, however, remain controversial.Methods and Results:Holter electrocardiography was performed in 11 LQTS infants before medication in early infancy, and in 11 age-matched control infants. Control infants were re-evaluated in late infancy. The power spectral density was calculated and parasympathetic activity and sympathovagal balance were obtained. Electrocardiograms of a representative hour during night-time sleep, daytime sleep, and daytime activity, were chosen and QT/RR intervals were manually measured. LQTS infants had significantly lower parasympathetic activity and higher sympathovagal balance during night-time sleep than control infants in early infancy. These autonomic conditions in early infancy were significantly depressed compared with late infancy. Corrected QT interval (QTc) during night-time sleep (490±20 ms) was significantly longer than that in daytime sleep (477±21 ms, P=0.04) or daytime activity (458±18 ms, P=0.003) in LQTS infants, and significantly longer than that during night-time sleep in controls.

CONCLUSIONS

A combination of the longest QTc and autonomic imbalance during night-time sleep in early infancy may be responsible for development of life-threatening arrhythmia in LQTS infants. Critical cases should be included in future studies.

Quantity and Quality of Carbohydrate Intake during Pregnancy, Newborn Body Fatness and Cardiac Autonomic Control: Conferred Cardiovascular Risk?

The fetal environment has an important influence on health and disease over the life course. Maternal nutritional status during pregnancy is potentially a powerful contributor to the intrauterine environment, and may alter offspring physiology and later life cardio-metabolic risk. Putative early life markers of cardio-metabolic risk include newborn body fatness and cardiac autonomic control. We sought to determine whether maternal dietary carbohydrate quantity and/or quality during pregnancy are associated with newborn body composition and cardiac autonomic function. Maternal diet during pregnancy was assessed in 142 mother-infant pairs using a validated food frequency questionnaire. Infant adiposity and body composition were assessed at birth using air-displacement plethysmography. Cardiac autonomic function was assessed as heart rate variability. The quantity of carbohydrates consumed during pregnancy, as a percentage of total energy intake, was not associated with meaningful differences in offspring birth weight, adiposity or heart rate variability (p > 0.05). There was some evidence that maternal carbohydrate quality, specifically higher fibre and lower glycemic index, is associated with higher heart rate variability in the newborn offspring (p = 0.06). This suggests that poor maternal carbohydrate quality may be an important population-level inter-generational risk factor for later cardiac and hemodynamic risk of their offspring.

Sudden infant death syndrome and inherited cardiac conditions

Sudden infant death syndrome (SIDS) is the leading cause of post-neonatal infant mortality in developed countries, characterized by the death of infants for no obvious reason and without prior warning. The complex interaction of multiple factors in the pathogenesis of SIDS is illustrated by the 'triple risk hypothesis', which proposed that SIDS results from a convergence of three overlapping risk factors: a critical developmental period, an exogenous stressor, and underlying genetic and/or nongenetic vulnerability in the infant. Rare variants in genes associated with inherited arrhythmia syndromes and cardiomyopathies have been proposed as the substrate for an infant's critical vulnerability in a small subset of SIDS cases. Given the potential risk of inherited cardiac disease, current guidelines recommend post-mortem genetic testing (molecular autopsy) and cardiological investigation of the surviving family, complemented by targeted genetic testing if appropriate. In this Review, we highlight the latest developments in understanding the spectrum and prevalence of cardiac-mediated SIDS, and discuss the clinical implications of SIDS in the surviving family and the general population.

Heart Rate Variability in Newborns

Heart rate (HR) and heart rate variability (HRV) in newborns is influenced by genetic determinants, gestational and postnatal age, and other variables. Premature infants have a reduced HRV. In neonatal HRV evaluated by spectral analysis, a dominant activity can be found in low frequency (LF) band (combined parasympathetic and sympathetic component). During the first postnatal days the activity in the high frequency (HF) band (parasympathetic component) rises, together with an increase in LF band and total HRV. Hypotrophy in newborn can cause less mature autonomic cardiac control with a higher contribution of sympathetic activity to HRV as demonstrated by sequence plot analysis. During quiet sleep (QS) in newborns HF oscillations increase – a phenomenon less expressed or missing in premature infants. In active sleep (AS), HRV is enhanced in contrast to reduced activity in HF band due to the rise of spectral activity in LF band. Comparison of the HR and HRV in newborns born by physiological vaginal delivery, without (VD) and with epidural anesthesia (EDA) and via sectio cesarea (SC) showed no significant differences in HR and in HRV time domain parameters. Analysis in the frequency domain revealed, that the lowest sympathetic activity in chronotropic cardiac chronotropic regulation is in the VD group. Different neonatal pathological states can be associated with a reduction of HRV and an improvement in the health conditions is followed by changes in HRV what can be use as a possible prognostic marker. Examination of heart rate variability in neonatology can provide information on the maturity of the cardiac chronotropic regulation in early postnatal life, on postnatal adaptation and in pathological conditions about the potential dysregulation of cardiac function in newborns, especially in preterm infants.

Test-Retest Reliability of Pediatric Heart Rate Variability: A Meta-Analysis

Heart rate variability (HRV), an established index of autonomic cardiovascular modulation, is associated with health outcomes (e.g., obesity, diabetes) and mortality risk. Time- and frequency-domain HRV measures are commonly reported in longitudinal adult and pediatric studies of health. While test-retest reliability has been established among adults, less is known about the psychometric properties of HRV among infants, children, and adolescents. The objective was to conduct a meta-analysis of the test-retest reliability of time- and frequency-domain HRV measures from infancy to adolescence. Electronic searches (PubMed, PsycINFO; January 1970-December 2014) identified studies with nonclinical samples aged ≤ 18 years; ≥ 2 baseline HRV recordings separated by ≥ 1 day; and sufficient data for effect size computation. Forty-nine studies (N = 5,170) met inclusion criteria. Methodological variables coded included factors relevant to study protocol, sample characteristics, electrocardiogram (ECG) signal acquisition and preprocessing, and HRV analytical decisions. Fisher's Z was derived as the common effect size. Analyses were age-stratified (infant/toddler < 5 years, n = 3,329; child/adolescent 5-18 years, n = 1,841) due to marked methodological differences across the pediatric literature. Meta-analytic results revealed HRV demonstrated moderate reliability; child/adolescent studies (Z = 0.62, r = 0.55) had significantly higher reliability than infant/toddler studies (Z = 0.42, r = 0.40). Relative to other reported measures, HF exhibited the highest reliability among infant/toddler studies (Z = 0.42, r = 0.40), while rMSSD exhibited the highest reliability among child/adolescent studies (Z = 1.00, r = 0.76). Moderator analyses indicated greater reliability with shorter test-retest interval length, reported exclusion criteria based on medical illness/condition, lower proportion of males, prerecording acclimatization period, and longer recording duration; differences were noted across age groups. HRV is reliable among pediatric samples. Reliability is sensitive to pertinent methodological decisions that require careful consideration by the researcher. Limited methodological reporting precluded several a priori moderator analyses. Suggestions for future research, including standards specified by Task Force Guidelines, are discussed.

Sudden Unexpected Death in Fetal Life Through Early Childhood

In March 2015, the Eunice Kennedy Shriver National Institute of Child Health and Human Development held a workshop entitled "Sudden Unexpected Death in Fetal Life Through Early Childhood: New Opportunities." Its objective was to advance efforts to understand and ultimately prevent sudden deaths in early life, by considering their pathogenesis as a potential continuum with some commonalities in biological origins or pathways. A second objective of this meeting was to highlight current issues surrounding the classification of sudden infant death syndrome (SIDS), and the implications of variations in the use of the term "SIDS" in forensic practice, and pediatric care and research. The proceedings reflected the most current knowledge and understanding of the origins and biology of vulnerability to sudden unexpected death, and its environmental triggers. Participants were encouraged to consider the application of new technologies and "omics" approaches to accelerate research. The major advances in delineating the intrinsic vulnerabilities to sudden death in early life have come from epidemiologic, neural, cardiac, metabolic, genetic, and physiologic research, with some commonalities among cases of unexplained stillbirth, SIDS, and sudden unexplained death in childhood observed. It was emphasized that investigations of sudden unexpected death are inconsistent, varying by jurisdiction, as are the education, certification practices, and experience of death certifiers. In addition, there is no practical consensus on the use of "SIDS" as a determination in cause of death. Major clinical, forensic, and scientific areas are identified for future research.

Dummy/pacifier use in preterm infants increases blood pressure and improves heart rate control

BACKGROUND

Preterm infants are at increased risk of sudden infant death syndrome (SIDS). Use of a dummy/pacifier is thought to be protective against SIDS; accordingly, we assessed the effects of dummy/pacifier use on blood pressure, cerebral oxygenation, and heart rate control over the first 6 mo of life after term corrected age (CA) when SIDS risk is greatest.

METHODS

Thirty-five preterm infants were studied longitudinally at 2-4 wk, 2-3 mo, and 5-6 mo CA. Cardiac control was assessed from spectral indices of heart rate variability (HRV) in the low frequency (LF) and the high frequency (HF) range, and the ratio of HF/LF indicating sympathovagal balance was calculated.

RESULTS

Overall, at 2-3 mo, mean arterial pressure was significantly higher in the supine position in dummy/pacifier users in both quiet sleep (70 ± 2 vs. 60 ± 2 mm Hg; P < 0.05) and active sleep (74 ± 3 vs. 69 ± 2 mm Hg; P < 0.05). Dummy/pacifier users had higher LF HRV and LF/HF ratio and lower HF HRV.

CONCLUSION

Dummy/pacifier use increased blood pressure during sleep, at the age of greatest SIDS risk. Overall, LF HRV was elevated and HF HRV reduced in dummy/pacifier users, suggesting that dummy use alters cardiac control in preterm infants.

The normal electrocardiograms in the conscious newborn lambs in neonatal period and its progression

BACKGROUND

Veterinary cardiology, especially electrocardiography, has shown major advancements for all animal species. Consequently, the number of ovine species used as experimental animals has increased to date. Few studies have been published on ovine systematic electrocardiography, particularly with respect to lamb physiology and neonatology. This study aimed to standardize the values of normal waves, complexes, and intervals of the electrocardiogram (ECG) in clinically Bergamasca healthy neonatal lambs, used as experimental animals. Serial computerized electrocardiography was performed in 10 male and 12 female neonates on the 1st, 7th, 14th, 21st, 28th, and 35th days of age. The following parameters were analyzed: heart rate and rhythm, duration and amplitude of waves, duration of intervals, and heart electrical axis.

RESULTS

During the first 35 days of life, (1) the sinusal heart rhythm was predominant, (2) there was a progressive decrease in the heart rate and R and T wave amplitude, and (3) a progressive increase in the PR, QT, and RR intervals. Finally, we confirmed that various components of neonatal evolution were more discernible in the augmented unipolar leads (aVF), which we recommend should be preferentially used in future studies. No significant statistical alterations were observed between males and females in relation to the analyzed parameters.

CONCLUSIONS

The information assimilated in this study is anticipated to enhance the diagnosis of multiple congenital heart defects in Bergamasca lambs and could be implemented in studies that use ovine species as experimental models.

The Effect of Gestational Age at Birth on Post-Term Maturation of Heart Rate Variability

STUDY OBJECTIVE

Preterm birth delays maturation of autonomic cardiovascular control, reflected in reduced heart rate variability (HRV) in preterm compared to term infants at term-equivalent age. It has been suggested that immature cardiovascular control contributes to the increased risk for the sudden infant death syndrome (SIDS) in preterm infants. However, the effects of prone sleeping, the major SIDS risk factor, and of gestational age (GA) at birth on HRV have not been assessed in preterm infants beyond term-equivalent age.

SUBJECTS AND METHODS

Very preterm (n = 21; mean GA 29.4 ± 0.3 weeks), preterm (n = 14; mean GA 33.5 ± 0.3 weeks), and term (n = 17; mean GA 40.1 ± 0.3 weeks) infants were recruited and underwent daytime polysomnography at 2-4 weeks, 2-3 months, and 5-6 months post-term corrected age (CA). Infants slept both supine and prone. HRV was assessed in the low frequency (LF) and high frequency (HF) ranges.

RESULTS

There was no effect of prone sleeping on HRV parameters in either preterm group. In term infants LF/HF was significantly elevated in the prone position in AS at 2-4 weeks (P < 0.05). HF HRV was significantly reduced (P < 0.05) and LF/HF increased (P < 0.05) in very preterm compared to both preterm and term infants at 2-3 months CA.

CONCLUSION

Prone sleeping did not significantly impact on heart rate variability (HRV) in preterm infants. However, reduced maturation of high frequency HRV in very preterm infants resulted in significantly altered sympathovagal balance at 2-3 months corrected age, the age of peak sudden infant death syndrome (SIDS) risk. This may contribute to the increased risk of SIDS in infants born at earlier gestational age.

Strengths and limitations of current pediatric blood pressure nomograms: a global overview with a special emphasis on regional differences in neonates and infants

The availability of robust nomograms is essential for the correct evaluation of blood pressure (BP) values in children. A literature search was conducted by accessing the National Library of Medicine by using the keywords BP, pediatric and reference values/nomograms. A total of 43 studies that evaluated pediatric BP nomograms were included in this review. Despite the accuracy of the latest studies, many numerical and methodological limitations still remain. The numerical limitations include the paucity of data for neonates/infants and for some geographic areas (Africa/South America/East Europe/Asia) and ethnicities. Furthermore, the data on ambulatory BP and response to exercise are extremely limited, and the criteria for stress-test interruption are lacking. There was heterogeneity in the methodologies employed to perform the measurements, in the inclusion/exclusion criteria (often not reported), in the data normalization and the data expression (Z-scores/percentiles/mean values). Although most studies adjusted the measurements for age and/or height, the classification by specific age/height subgroups varied. Gender differences were generally considered, whereas other confounders (that is, ethnicity/geographic area/environment) were seldom evaluated. As a result, nomograms were heterogeneous, and when comparable, at times showed widely different confidence intervals. These differences are most likely because of both methodological limitations and differences among the populations studied. Some robust nomograms exist (particularly those from the USA); however, it has been demonstrated that if adopted in other countries/continents, they may generate an unpredictable bias in the evaluation of BP values in children. Actual pediatric BP nomograms present consistent limitations that affect the evaluation of BP in children. Comprehensive nomograms, which are based on a large population of healthy children (including neonates/infants) and use standardized methodology, are warranted for every country/region.

Heart rate variability during caregiving and sleep after massage therapy in preterm infants

BACKGROUND

Preterm birth impairs the infant's stress response due to interruption of autonomic nervous system (ANS) development. Preterm infants demonstrate a prolonged and aberrant sympathetic response to stressors. ANS development may be promoted by massage therapy (MT), which has been shown to improve stress response in preterm infants.

AIMS

The aim of this study was to compare preterm infant ANS function and stress response during sleep and caregiving epochs, as measured by heart rate variability (HRV), after two weeks of twice-daily MT.

STUDY DESIGN

A subset of participants from a larger randomized, masked, controlled trial was used.

SUBJECTS

Twenty-one infants (8 males and 13 females) from a larger study of 37 medically stable preterm infants were studied. The infants were receiving full volume enteral feedings with a mean post-menstrual age of 31.4 (MT) and 30.9 (control) weeks.

OUTCOME MEASURES

Low to high frequency (LF:HF) ratio of HRV was the outcome of interest.

RESULTS

There was a significant group×time×sex interaction effect (p<.05). Male control infants demonstrated a significant decline in LF:HF ratio from baseline to the second caregiving epoch, suggesting decreased mobilization of sympathetic nervous system response when exposed to stressors. Male MT infants demonstrated increased LF:HF ratio during caregiving and decreased LF:HF ratio during sleep epochs, suggesting improved ANS function, although this was not statistically significant. LF:HF ratio was similar in female MT and female control infants during caregiving and sleep.

CONCLUSIONS

Control males had decreased HRV compared to MT males. There was no difference in HRV between MT and control females.

Autonomic cardiac innervation: development and adult plasticity

Autonomic cardiac neurons have a common origin in the neural crest but undergo distinct developmental differentiation as they mature toward their adult phenotype. Progenitor cells respond to repulsive cues during migration, followed by differentiation cues from paracrine sources that promote neurochemistry and differentiation. When autonomic axons start to innervate cardiac tissue, neurotrophic factors from vascular tissue are essential for maintenance of neurons before they reach their targets, upon which target-derived trophic factors take over final maturation, synaptic strength and postnatal survival. Although target-derived neurotrophins have a central role to play in development, alternative sources of neurotrophins may also modulate innervation. Both developing and adult sympathetic neurons express proNGF, and adult parasympathetic cardiac ganglion neurons also synthesize and release NGF. The physiological function of these “non-classical” cardiac sources of neurotrophins remains to be determined, especially in relation to autocrine/paracrine sustenance during development.

 

Cardiac autonomic nerves are closely spatially associated in cardiac plexuses, ganglia and pacemaker regions and so are sensitive to release of neurotransmitter, neuropeptides and trophic factors from adjacent nerves. As such, in many cardiac pathologies, it is an imbalance within the two arms of the autonomic system that is critical for disease progression. Although this crosstalk between sympathetic and parasympathetic nerves has been well established for adult nerves, it is unclear whether a degree of paracrine regulation occurs across the autonomic limbs during development. Aberrant nerve remodeling is a common occurrence in many adult cardiovascular pathologies, and the mechanisms regulating outgrowth or denervation are disparate. However, autonomic neurons display considerable plasticity in this regard with neurotrophins and inflammatory cytokines having a central regulatory function, including in possible neurotransmitter changes. Certainly, neurotrophins and cytokines regulate transcriptional factors in adult autonomic neurons that have vital differentiation roles in development. Particularly for parasympathetic cardiac ganglion neurons, additional examinations of developmental regulatory mechanisms will potentially aid in understanding attenuated parasympathetic function in a number of conditions, including heart failure.

Developmental changes in GABAergic neurotransmission to presympathetic and cardiac parasympathetic neurons in the brainstem

Cardiovascular function is regulated by a dynamic balance composed of sympathetic and parasympathetic activity. Sympathoexcitatory presympathetic neurons (PSNs) in the rostral ventrolateral medulla project directly to cardiac and vasomotor sympathetic preganglionic neurons in the spinal cord. In proximity to the PSNs in the medulla, there are preganglionic cardiac vagal neurons (CVNs) within the nucleus ambiguus, which are critical for parasympathetic control of heart rate. Both CVNs and PSNs receive GABAergic synaptic inputs that change with challenges such as hypoxia and hypercapnia (H/H). Autonomic control of cardiovascular function undergoes significant changes during early postnatal development; however, little is known regarding postnatal maturation of GABAergic neurotransmission to these neurons. In this study, we compared changes in GABAergic inhibitory postsynaptic currents (IPSCs) in CVNs and PSNs under control conditions and during H/H in postnatal day 2-5 (P5), 16-20 (P20), and 27-30 (P30) rats using an in vitro brainstem slice preparation. There was a significant enhancement in GABAergic neurotransmission to both CVNs and PSNs at age P20 compared with P5 and P30, with a more pronounced increase in PSNs. H/H did not significantly alter this enhanced GABAergic neurotransmission to PSNs in P20 animals. However, the frequency of GABAergic IPSCs in PSNs was reduced by H/H in P5 and P30 animals. In CVNs, H/H elicited an inhibition of GABAergic neurotransmission in all ages studied, with the most pronounced inhibition occurring at P20. In conclusion, there are critical development periods at which significant rearrangement occurs in the central regulation of cardiovascular function.

Chemoreceptors, baroreceptors, and autonomic deregulation in children with obstructive sleep apnea

Obstructive sleep apnea (OSA) is highly prevalent sleep disorder of breathing in both adults and children that is fraught with substantial cardiovascular morbidities, the latter being attributable to a complex interplay between intermittent hypoxia (IH), episodic hypercapnia, recurrent large intra-thoracic pressure swings, and sleep disruption. Alterations in autonomic nervous system function could underlie the perturbations in cardiovascular, neurocognitive, immune, endocrine and metabolic functions that affect many of the patients suffering from OSA. Although these issues have received substantial attention in adults, the same has thus far failed to occur in children, creating a quasi misperception that children are protected. Here, we provide a critical overview of the evidence supporting the presence of autonomic nervous system (ANS) perturbations in children with OSA, draw some parallel assessments to known mechanisms in rodents and adult humans, particularly, peripheral and central chemoreceptor and baroreceptor pathways, and suggest future research directions.