Altered cardiovascular rhythmicity in children born small for gestational age

A longitudinal study of blood pressure circadian rhythm from childhood to early adulthood

Altered blood pressure (BP) circadian rhythmicity has been increasingly linked with cardiovascular risk. However, little is known about BP circadian rhythm change with age and its possible sociodemographic, anthropometric, and genetic moderators. Twenty-four-hour ambulatory BP was measured up to 16 times over a 23-year period in 339 European Americans (EAs) and 293 African Americans (AAs), with an average age of 15 years at the initial visit. BP circadian rhythms were indexed by amplitude and percent rhythm (a measure of rhythm integrity) and calculated using Fourier analysis. BP amplitude and percent rhythm increased with age and average BP (BP mesor). AAs were more likely to have lower BP amplitude and percent rhythm than their EA counterparts. BP amplitude and percent rhythm also decreased with adiposity (BMI and waist circumference). The summer season was associated with lower BP amplitude in AAs and lower percent rhythm in both AAs and EAs. Sex, height, socioeconomic status, physical activity, and family history of essential hypertension did not have an independent impact on BP amplitude or percent rhythm. The results of the present study suggest that BP circadian rhythm increases with age and BP mesor from childhood to young adulthood, decreases with adiposity, and that AAs are more likely to have lower circadian rhythm than EAs. Furthermore, we demonstrated that the summer season is associated with lower BP rhythmicity.

Cardiovascular rhythmicity in overweight and obese children

INTRODUCTION

Obesity is thought to play a role in the disruption of cardiac rhythmicity in obese children, but this is mostly an unexplored field of investigation. We aimed to evaluate the impact of overweight and obesity on circadian and ultradian cardiovascular rhythmicity of prepubertal children, in comparison with normal weight counterparts.

METHODS

We performed a cross sectional study of 316 children, followed in the birth cohort Generation XXI (Portugal). Anthropometrics and 24-hour ambulatory blood pressure were measured and profiles were examined with Fourier analysis for circadian and ultradian blood pressure (BP) and heart rate (HR) rhythms.

RESULTS

Overweight/obese children presented more frequently a non-dipping BP pattern than normal weight counterparts (31.5% vs. 21.6%, p = 0.047). The prevalence of 24-hour mean arterial pressure (MAP) and 8-hour HR rhythmicity was significantly lower in obese children (79.3% vs. 88.0%, p = 0.038 and 33.3% vs. 45.2%, p = 0.031, respectively). The prevalence of the remaining MAP and HR rhythmicity was similar in both groups. No differences were found in the median values of amplitudes and acrophases of MAP and HR rhythms.

DISCUSSION

The alterations found in rhythmicity suggest that circadian and ultradian rhythmicity analysis might be sensitive in detecting early cardiovascular dysregulations, but future studies are needed to reinforce our findings and to better understand their long-term implications.

Arterial stiffness and nocturnal hypertension in preterm children and adolescents

BACKGROUND AND OBJECTIVES

Preterm birth has been associated with increased risk for developing hypertension and other chronic diseases during childhood and adulthood. The aim of the current prospective case-control study was to investigate the associations of preterm birth with ambulatory blood pressure (BP) levels and arterial stiffness during childhood and adolescence.

METHODS

The study population included 52 children and adolescents born preterm and 26 healthy children born full term with similar age. The participants underwent ambulatory BP monitoring (ABPM) and assessment of carotid-femoral pulse wave velocity (PWV).

RESULTS

Preterm children presented higher night SBP z score values compared to controls, but did not differ in other ABPM parameters, office peripheral and central SBPs. Nocturnal hypertension was found in 78% (7/9) of ex-preterm children with ambulatory BP hypertension. Preterm birth was an independent predictor of PWV z score adjusted for heart rate. Estimated marginal means for PWV z score adjusted for age, sex, presence of kidney disease at birth, office BPs, night BPs, central SBP, and BMI z scores were significantly higher in preterm individuals compared to controls (0.703, 95% confidence interval [CI] 0.431-0.975 versus -0.19, 95% CI -0.574-0.536, respectively, P  = 0.027). Preterm children who were overweight presented the highest values of night SBP and PWV z score.

CONCLUSION

Preterm birth is associated with higher nocturnal BP and increased arterial stiffness in childhood and adolescence. Increased awareness for detection of hypertension and prevention of obesity in childhood could prevent future adverse cardiovascular outcomes in preterm individuals.

Neonatal hypertension: concerns within and beyond the neonatal intensive care unit

Neonatal hypertension occurs in 1%-2% of neonates in the neonatal intensive care unit (NICU) although may be underdiagnosed. Blood pressure values in premature neonates change rapidly in the first days and weeks of life which may make it more difficult to recognize abnormal blood pressure values. In addition, the proper blood pressure measurement technique must be used to ensure the accuracy of the measured values as most blood pressure devices are not manufactured specifically for this population. In premature neonates, the cause of the hypertension is most commonly related to prematurity-associated complications or management while in term neonates is more likely to be due to an underlying condition. Both oral and intravenous antihypertensive medications can be used in neonates to treat high blood pressure although none are approved for use in this population by regulatory agencies. The natural history of most neonatal hypertension is that it resolves over the first year or two of life. Of concern are the various neonatal risk factors for later cardiovascular and kidney disease that are present in most NICU graduates. Prematurity increases the risk of adulthood hypertension while intrauterine growth restriction may even lead to hypertension during childhood. From neonates through to adulthood NICU graduates, this review will cover each of these topics in more detail and highlight the aspects of blood pressure management that are established while also highlighting where knowledge gaps exist.

Ethnic differences and heritability of blood pressure circadian rhythm in African and European American youth and young adults

BACKGROUND

The aim of this study was to investigate whether blood pressure (BP) circadian rhythm in African Americans differed from that in European Americans. We further examined the genetic and/or environmental sources of variances of the BP circadian rhythm parameters and the extent to which they depend on ethnicity or sex.

METHOD

Quantification of BP circadian rhythm was obtained using Fourier transformation from the ambulatory BP monitoring data of 760 individuals (mean age, 17.2 ± 3.3; 322 twin pairs and 116 singletons; 351 African Americans).

RESULTS

BP circadian rhythm showed a clear difference by ethnic group with African Americans having a lower amplitude (P = 1.5e-08), a lower percentage rhythm (P = 2.8e-11), a higher MESOR (P = 2.5e-05) and being more likely not to display circadian rhythm (P = 0.002) or not in phase (P = 0.003). Familial aggregation was identified for amplitude, percentage rhythm and acrophase with genetic factors and common environmental factors together accounting for 23 to 33% of the total variance of these BP circadian rhythm parameters. Unique environmental factors were the largest contributor explaining up to 67--77% of the total variance of these parameters. No sex or ethnicity difference in the variance components of BP circadian rhythm was observed.

CONCLUSION

This study suggests that ethnic differences in BP circadian rhythm already exist in youth with African Americans having a dampened circadian rhythm and better BP circadian rhythm may be achieved by changes in environmental factors.

Circadian disruption and human health

Circadian disruption is pervasive and can occur at multiple organizational levels, contributing to poor health outcomes at individual and population levels. Evidence points to a bidirectional relationship, in that circadian disruption increases disease severity and many diseases can disrupt circadian rhythms. Importantly, circadian disruption can increase the risk for the expression and development of neurologic, psychiatric, cardiometabolic, and immune disorders. Thus, harnessing the rich findings from preclinical and translational research in circadian biology to enhance health via circadian-based approaches represents a unique opportunity for personalized/precision medicine and overall societal well-being. In this Review, we discuss the implications of circadian disruption for human health using a bench-to-bedside approach. Evidence from preclinical and translational science is applied to a clinical and population-based approach. Given the broad implications of circadian regulation for human health, this Review focuses its discussion on selected examples in neurologic, psychiatric, metabolic, cardiovascular, allergic, and immunologic disorders that highlight the interrelatedness between circadian disruption and human disease and the potential of circadian-based interventions, such as bright light therapy and exogenous melatonin, as well as chronotherapy to improve and/or modify disease outcomes.

Isolated nocturnal and isolated daytime hypertension associate with altered cardiovascular morphology and function in children with chronic kidney disease: findings from the Cardiovascular Comorbidity in Children with Chronic Kidney Disease study

INTRODUCTION

Prevalence of isolated nocturnal hypertension (INH) and isolated daytime hypertension (IDH) is around 10% in adults. Data in children, especially in chronic kidney disease (CKD), are lacking. The aim of this cross-sectional multicenter cohort study was to define the prevalence of INH and IDH and its association with cardiovascular morphology and function, that is, pulse wave velocity (PWV), carotid intima-media thickness (cIMT), or left ventricular mass index (LVMI) in children with CKD.

METHODS

Ambulatory blood pressure (BP) monitoring profiles were analyzed in 456 children with CKD stages III-V participating in the Cardiovascular Comorbidity in Children with Chronic Kidney Disease Study (64.3% males, 71.3% congenital anomaly of the kidney and urinary tract, age 12.5 ± 3.2 years, estimated glomerular filtration rate 29 ± 12 ml/min per 1.73 m). Baseline PWV, cIMT, and LVMI were compared in normotension, INH, IDH, or sustained 24-h hypertension.

RESULTS

Prevalence of sustained hypertension was 18.4%, of INH 13.4%, and of IDH 3.7%. PWV SDS (SD score) and cIMT SDS were significantly higher in sustained hypertension and INH, and PWV SDS was significantly higher in IDH, compared with normotension. LVMI was significantly increased in sustained hypertension, but not in INH or IDH. Determinants of INH were smallness for gestational age, older age, higher height SDS and parathyroid hormone, and shorter duration of CKD. In logistic regression analysis, day/night-time hypertension or ambulatory BP monitoring pattern (normal, INH, IDH, sustained hypertension) were independently associated with cardiovascular outcome measures: elevated night-time BP was associated with increased cIMT, PWV, and left ventricular hypertrophy; INH was associated with cIMT.

CONCLUSION

INH is present in almost one out of seven children with predialysis CKD; INH and nocturnal hypertension in general are associated with alterations of arterial morphology and function.

The role of parathyroid hormone during pregnancy on the relationship between maternal vitamin D deficiency and fetal growth restriction: a prospective birth cohort study

Previous studies have shown conflicting findings regarding the relationship between maternal vitamin D deficiency (VDD) and fetal growth restriction (FGR). We hypothesised that parathyroid hormone (PTH) may be an underlying factor relevant to this potential association. In a prospective birth cohort study, descriptive statistics were evaluated for the demographic characteristics of 3407 pregnancies in the second trimester from three antenatal clinics in Hefei, China. The association of the combined status of vitamin D and PTH with birth weight and the risk of small for gestational age (SGA) was assessed by a multivariate linear and binary logistic regression. We found that declined status of 25-hydroxyvitamin D is associated with lower birth weight (for moderate VDD: adjusted β = -49·4 g, 95 % CI -91·1, -7·8, P < 0·05; for severe VDD: adjusted β = -79·8 g, 95 % CI -127·2, -32·5, P < 0·01), as well as ascended levels of PTH (for elevated PTH: adjusted β = -44·5 g, 95 % CI -82·6, -6·4, P < 0·05). Compared with the non-VDD group with non-elevated PTH, pregnancies with severe VDD and elevated PTH had the lowest neonatal birth weight (adjusted β = -124·7 g, 95 % CI -194·6, -54·8, P < 0·001) and the highest risk of SGA (adjusted risk ratio (RR) = 3·36, 95 % CI 1·41, 8·03, P < 0·01). Notably, the highest risk of less Ca supplementation was founded in severe VDD group with elevated PTH (adjusted RR = 4·67, 95 % CI 2·78, 7·85, P < 0·001). In conclusion, elevated PTH induced by less Ca supplementation would further aggravate the risk of FGR in pregnancies with severe VDD through impaired maternal Ca metabolism homoeostasis.

The Childhood Role in Development of Primary Hypertension

Primary hypertension is not just an adult disorder. Current US population data on children and adolescents demonstrate a prevalence of elevated blood pressure (BP) and hypertension combined of over 10%. Recent reports from prospective cohort studies describe an association of high BP in childhood with hypertension in young adulthood. Excess adiposity is strongly associated with higher BP in childhood and increases risk for hypertension in adulthood. In addition to overweight/obesity, other exposures that raise the risk for high BP include low birthweight, dietary sodium, and stress. Using intermediate markers of cardiovascular injury, studies on hypertensive children report findings of cardiac hypertrophy, vascular stiffness, and early atherosclerotic changes. Impaired cognitive function has also been demonstrated in hypertensive children. Recent advances in clinical and translational research support the concept that the evolution of primary hypertension begins in childhood.

Prevalence of Hypertension in Children with Early-Stage ADPKD

BACKGROUND AND OBJECTIVES

Autosomal dominant polycystic kidney disease is the most common inheritable kidney disease, frequently thought to become symptomatic in adulthood. However, patients with autosomal dominant polycystic kidney disease may develop signs or symptoms during childhood, in particular hypertension. Although ambulatory BP monitoring is the preferred method to diagnose hypertension in pediatrics, data in children with autosomal dominant polycystic kidney disease are limited.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our retrospective multicenter study was conducted to collect ambulatory BP monitoring recordings from patients with autosomal dominant polycystic kidney disease age <18 years old. Basic anthropometric parameters as well as data on kidney function, BP treatment, and kidney ultrasound were also collected.

RESULTS

Data from 310 children with autosomal dominant polycystic kidney disease with a mean age of 11.5±4.1 years old were collected at 22 European centers. At the time when ambulatory BP monitoring was performed, 95% of children had normal kidney function. Reference data for ambulatory BP monitoring were available for 292 patients. The prevalence rates of children with hypertension and/or those who were treated with antihypertensive drugs were 31%, 42%, and 35% during daytime, nighttime, or the entire 24-hour cycle, respectively. In addition, 52% of participants lacked a physiologic nocturnal BP dipping, and 18% had isolated nocturnal hypertension. Logistic regression analysis showed a significant association between a categorical cyst score that was calculated on the basis of the number of cysts >1 cm per kidney and daytime hypertension (odds ratio, 1.70; 95% confidence interval, 1.21 to 2.4; P=0.002), nighttime hypertension (odds ratio, 1.31; 95% confidence interval, 1.05 to 1.63; P=0.02), or 24-hour hypertension (odds ratio, 1.39; 95% confidence interval, 1.08 to 1.81; P=0.01). Kidney length, expressed as SD score, was also significantly associated with nighttime hypertension (odds ratio, 1.23; 95% confidence interval, 1.06 to 1.42; P=0.10).

CONCLUSIONS

These data indicate high prevalence of hypertension in children with autosomal dominant polycystic kidney disease starting at young ages.

Fetal-growth-restricted preterm infants display compromised autonomic cardiovascular control on the first postnatal day but not during infancy

BackgroundFetal growth restriction (FGR) is associated with increased perinatal mortality and long-term cardiovascular and neurodevelopmental sequelae. We hypothesized that FGR impacts on the development of autonomic heart rate and blood pressure control, contributing to unfavorable short- and long-term outcomes following FGR.MethodsWe studied 25 preterm FGR and 22 preterm and 19 term appropriate for gestational age (AGA) infants. Preterm neonates were studied on postnatal day 1, and all infants were studied at 1 and 6 months post-term age. To investigate autonomic cardiovascular control, we examined heart rate variability (HRV) and baroreflex sensitivity using spectral power and transfer-function analyses.ResultsPreterm FGR neonates exhibited higher heart rates and reduced HRV compared with preterm AGA controls on postnatal day 1. No significant differences were found between the three groups at 1 or 6 months post-term age.ConclusionPreterm FGR neonates display compromised HRV on postnatal day 1, which may suggest increased vulnerability to circulatory instability. This may predispose these neonates to systemic and cerebral hypoperfusion and increase the risk of long-term neurodevelopmental sequelae. Differences were no longer found at 1 and 6 months post-term age, suggesting that the maturation of autonomic cardiovascular control may be preserved following FGR.

Association between maternal vitamin D deficiency and small for gestational age: evidence from a meta-analysis of prospective cohort studies

OBJECTIVE

To determine whether maternal vitamin D deficiency during pregnancy is associated with small for gestational age (SGA).

METHODS

A comprehensive literature search of PubMed, the Cochrane Library, Embase, and the Elsevier ScienceDirect library was conducted to identify relevant articles reporting prospective cohort studies in English, with the last report included published in February 2017. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were used to evaluate the correlation in a random effects model.

RESULTS

A total of 13 cohort studies were included in this meta-analysis with a sample of 28 285 individuals from seven countries. The pooled overall OR for babies born SGA was 1.588 (95% CI 1.138 to 2.216; p<0.01) for women with vitamin D deficiency. The prevalence of vitamin D deficiency during pregnancy varied from 13.2% to 77.3%. Subgroup analyses identified no significant differences in the association between vitamin D deficiency and SGA based on study quality, gestational week during which blood sampling was performed, cut-off vitamin D levels, sample size, adjustment for critical confounders and method for measuring vitamin D.

CONCLUSION

This meta-analysis suggests that vitamin D deficiency is associated with an increased risk of SGA.

Circadian and ultradian cardiovascular rhythmicity in obese children

Altered circadian and ultradian blood pressure (BP) and heart rate (HR) rhythmicity have been described in diseases with increased cardiovascular risk. We analyzed cardiovascular rhythmicity in obese children. BP and HR rhythmicity was assessed with Fourier analysis from 24-h ambulatory BP measurements in 75 obese children and compared with an age- and gender-matched, lean healthy reference group of 150 subjects. Multivariate regression analysis was applied to identify significant independent factors explaining variability of rhythmicity. Prevalence of 24- and 6-h BP rhythmicity in the obese group was lower (p = 0.03 and p = 0.02), whereas the prevalence of HR rhythmicity was comparable in both groups. Excluding hypertensive participants, the results remained similar. Twenty-four-hour BP and HR acrophase were delayed in obese children (p = 0.004, p < 0.0001), 24-h BP amplitude did not differ (p = 0.07), and 24-h HR amplitude was blunted (p = < 0.0001). BP Mesor in the obese group was higher (p = 0.02); HR Mesor did not differ (p = 0.1). Multivariate regression analysis failed to identify a single anthropometric or blood pressure parameter explaining the variability of BP and HR rhythmicity.

CONCLUSION

Prevalence and parameters of circadian and ultradian BP and HR rhythmicity in obese children are altered compared to a healthy reference group, independent of preexisting hypertension.

WHAT IS KNOWN

• Altered cardiovascular rhythmicity has been described in children with different diseases such as primary hypertension or chronic renal failure. What is New: • This study reveals altered cardiovascular rhythmicity in obese children compared to an age and gender-matched healthy reference group independent from preexisting hypertension.

Blood pressure (BP) assessment-from BP level to BP variability

The assessment of blood pressure (BP) can be challenging in children, especially in very young individuals, due to their variable body size and lack of cooperation. In the absence of data relating BP with cardiovascular outcomes in children, there is a need to convert absolute BP values (in mmHg) into age-, gender- and height appropriate BP percentiles or Z-scores in order to compare a patient's BP with the BP of healthy children of the same age, but also of children of different ages. Traditionally, the interpretation of BP has been based mainly on the assessment of the BP level obtained by office, home or 24-h BP monitoring. Recent studies suggest that it is not only BP level (i.e. average BP) but also BP variability that is clinically important for the development of target organ damage, including the progression of chronic kidney disease. In this review we describe current methods to evaluate of BP level, outline available methods for BP variability assessment and discuss the clinical consequences of BP variability, including its potential role in the management of hypertension.

Birth weight and arterial hypertension

PURPOSE OF REVIEW

To provide an overview of available evidence of the relationship between birth weight and future hypertension development.

RECENT FINDINGS

Fetal programming plays a significant role in future hypertension. Both low and high birth weight are able to influence weight gain during childhood, adult weight and blood pressure values during childhood and adulthood. To date, an increasing amount of evidence is available especially for the relationship between low birth weight and hypertension, supported also by pathophysiological studies.

SUMMARY

In the era of personalized medicine, the possibility to reduce cardiovascular risk before or soon after birth and intervene on risk factors during childhood is appealing and promising for the future.

Familial aggregation and childhood blood pressure

There is growing concern about elevated blood pressure (BP) in children. The evidence for familial aggregation of childhood BP is substantial. Twin studies have shown that a large part of the familial aggregation of childhood BP is due to genes. The first part of this review provides the latest progress in gene finding for childhood BP, focusing on the combined effects of multiple loci identified from the genome-wide association studies on adult BP. We further review the evidence on the contribution of the genetic components of other family risk factors to the familial aggregation of childhood BP including obesity, birth weight, sleep quality, sodium intake, parental smoking, and socioeconomic status. At the end, we emphasize the promise of using genomic-relatedness-matrix restricted maximum likelihood (GREML) analysis, a method that uses genome-wide data from unrelated individuals, in answering a number of unsolved questions in the familial aggregation of childhood BP.

Recent clinical and translational advances in pediatric hypertension

Epidemiological reports describe a child population increase in BP level and an increase in prevalence of hypertension, that is largely, but not entirely, driven by a concurrent increase in childhood obesity. Given current estimates, ≈10% of adolescents have hypertension or prehypertension. In addition to obesity, dietary salt intake and waist circumference, a marker of visceral obesity, are found to be independently associated with the rise in BP among children and adolescents. Dietary salt intake in urban children is well above recommended levels largely because of consumption of processed and fast foods. Childhood exposures, such as stress,52 salt, and fructose, as well as lifestyles, including food sources, sleep patterns, and reductions in physical activity may have a role in obesity-high BP associations. In addition, clinical and translational evidence is mounting that intrauterine exposures alter can effect changes in fetal development that have an enduring effect on cardiovascular and metabolic function later in life. These effects can be detected even in children who are products of a term otherwise normal pregnancy. Hypertension in childhood has been defined statistically (BP ≥ 95th percentile) because of lack of outcome data that links a BP level with heightened risk for future cardiovascular events. Therefore, primary hypertension had been considered a risk factor for later hypertension in adulthood. Intermediate markers of TOD, including cardiac hypertrophy, vascular stiffness, and increases in cIMT, are detectable in adolescents with primary hypertension. Evidence that vascular injury is present in the early phase of hypertension and even in prehypertension warrants consideration on the current definition of pediatric hypertension. With further studies on TOD and other risk factors in addition to high BP, it may be possible to shift from a statistical definition to a definition of childhood hypertension that is evidence based. Preventing or reducing childhood obesity would have substantial benefit in countering the documented increase in BP levels and prevalence of high BP in childhood. Weight control in overweight and obese children, along with dietary changes 53 and increases in physical activity,54 has benefit on BP levels in childhood. Prevention of childhood obesity and BP risk will require multiple levels of intervention, including public health, health policy, and attention to food supply to foster the necessary lifestyle changes to prevent and reduce childhood obesity.

Autonomic nervous system dysregulation in pediatric hypertension

Historically, primary hypertension (HTN) has been prevalent typically in adults. Recent data however, suggests an increasing number of children diagnosed with primary HTN, mainly in the setting of obesity. One of the factors considered in the etiology of HTN is the autonomous nervous system, namely its dysregulation. In the past, the sympathetic nervous system (SNS) was regarded as a system engaged mostly in buffering major acute changes in blood pressure (BP), in response to physical and emotional stressors. Recent evidence suggests that the SNS plays a much broader role in the regulation of BP, including the development and maintenance of sustained HTN by a chronically elevated central sympathetic tone in adults and children with central/visceral obesity. Consequently, attempts have been made to reduce the SNS hyperactivity, in order to intervene early in the course of the disease and prevent HTN-related complications later in life.

Hypertension in children with obesity

The prevalence of obesity related hypertension has dramatically increased in children with the parallel increase in pediatric obesity. This pediatric health problem may adversely affect cardiovascular health in adult life. The pathogenesis of hypertension in obese children is not widely understood. We therefore undertake this review to raise public awareness. Early childhood parameters like birth weight and postnatal weight gain may play important roles in risk for obesity and obesity related hypertension later in childhood and adult life. Further information is required to confirm this origin of hypertension so that appropriate measures are taken in the peri-natal period. The role of sympathetic nervous system has now been well established as one of the principle mechanisms involved in obesity related hypertension. The Renin-Angiotensin system, insulin resistance due to obesity and as a part of metabolic syndrome along with imbalance in adipokines such as leptin and adiponectin, cause activation of the sympathetic system, vasoconstriction, endothelial dysfunction and sodium reabsorption among other perturbations. Multi-step interventions targeting these various mechanisms are required to break the cycle of obesity and metabolic syndrome. Vitamin D deficiency, sleep apnea due to airway obstruction and hyperuricemia may also play a significant role and should not be ignored in its early stages. Obesity is a risk factor for other co-morbid conditions like chronic kidney disease and fatty liver which further accentuate the risk of hypertension. Increased awareness is required to prevent, diagnose and treat obesity related hypertension among the pediatric population.

Primary hypertension in childhood

There is growing concern about elevated blood pressure in children and adolescents, because of its association with the obesity epidemic. Moreover, cardiovascular function and blood pressure level are determined in childhood and track into adulthood. Primary hypertension in childhood is defined by persistent blood pressure values ≥ the 95th percentile and without a secondary cause. Preventable risk factors for elevated blood pressure in childhood are overweight, dietary habits, salt intake, sedentary lifestyle, poor sleep quality and passive smoking, whereas non-preventable risk factors include race, gender, genetic background, low birth weight, prematurity, and socioeconomic inequalities. Several different pathways are implicated in the development of primary hypertension, including obesity, insulin resistance, activation of the sympathetic nervous system, alterations in sodium homeostasis, renin-angiotensin system and altered vascular function. Prevention of adult cardiovascular disease should begin in childhood by regularly screening for high blood pressure, counseling for healthy lifestyle and avoiding preventable risk factors.

Reduced respiratory sinus arrhythmia in adults born at extremely low birth weight: evidence of premature parasympathetic decline?

Individuals born at extremely low birth weight (ELBW; <1000 g) are exposed to early adversity in multiple forms. Given that substantial development of the autonomic nervous system (ANS) occurs during the third trimester of gestation, ANS functioning may be altered in adults who were born before reaching 28 weeks of gestational age. The aims of the study were to: (1) determine whether two indices of ANS functioning [resting heart period (HP) and respiratory sinus arrhythmia (RSA)], differed between adult ELBW survivors and normal birth weight (NBW) controls, and (2) ascertain whether ANS functioning was differentially vulnerable to age-related decline in the ELBW participants. Resting HP and RSA (reflecting cardiac efficiency and responsive cardiac control, respectively) were assessed in 30 non-impaired ELBW survivors and 47 NBW controls at ages 22-26 and again at 30-35 years. At each assessment, resting RSA was significantly lower in the ELBW group than in the NBW comparison group. In addition, individual differences in RSA within the ELBW group were poorly preserved over time. These findings are suggestive of a premature decline in parasympathetic functioning in some adult ELBW survivors.

Nocturnal blood pressure non-dipping is prevalent in severely obese, prepubertal and early pubertal children

AIM

To investigate the prevalence of nocturnal blood pressure dipping among obese prepubertal and early pubertal children and to analyse the relationship between dipping and measures of insulin-glucose metabolism or sleep-disordered breathing.

METHODS

We studied 76 obese children (41% girls) under clinical care, with an average age of 10.4 ± 1.7 and a body mass index Z-score (BMI Z-score) of 6.2 ± 1.6. We performed a 24-h ambulatory blood pressure measurement. Non-dipping was defined as a nocturnal blood pressure reduction of <10%. We calculated measures of insulin-glucose metabolism from the performed frequently sampled intravenous glucose-tolerance test and from fasting blood samples. Overnight sleep polygraph recordings were performed to assess sleep-disordered breathing.

RESULTS

Forty-two percent of the children were systolic non-dippers, and 17% were diastolic non-dippers. There were no associations between systolic or diastolic dipping and measures of insulin-glucose metabolism after adjustments for BMI Z-score, gender and pubertal status. There were no associations between dipping and measures of sleep-disordered breathing.

CONCLUSION

Nocturnal non-dipping was two times higher among severely obese, prepubertal and early pubertal children, compared to previous reports among children in general. There were no associations between nocturnal dipping and insulin-glucose metabolism or measures of sleep-disordered breathing in this group.

Blood pressure rhythmicity and visceral fat in children with hypertension

Primary hypertension is associated with disturbed activity of the sympathetic nervous system and altered blood pressure rhythmicity. We analyzed changes in cardiovascular rhythmicity and its relation with target organ damage during 12 months of antihypertensive treatment in 50 boys with hypertension (median, 15.0 years). The following parameters were obtained before and after 12 months of antihypertensive treatment: 24-hour ambulatory blood pressure, left ventricular mass, carotid intima-media thickness, and MRI for visceral and subcutaneous adipose tissue. Amplitudes and acrophases of mean arterial pressure and heart rate rhythms were obtained for 24-, 12-, and 8-hour periods. After 1 year of treatment, 68% of patients were normotensive, and left ventricular mass and carotid intima-media thickness decreased in 60% and 62% of patients, respectively. Blood pressure and heart rate rhythmicity patterns did not change. Changes in blood pressure amplitude correlated with the decrease of waist circumference (P=0.035). Moreover, the decrease of visceral fat correlated with the decrease of 24-hour mean arterial pressure and heart rate acrophases (both P<0.05). There were no differences in changes of blood pressure and heart rate rhythms between patients who achieved or did not achieve normotension and regression of left ventricular mass and carotid intima-media thickness. It was concluded that abnormal cardiovascular rhythmicity persists in children with primary hypertension despite effective antihypertensive treatment, which suggests that it may be the primary abnormality. The correlation between changes in cardiovascular rhythmicity and visceral obesity may indicate that the visceral fat plays an important role in the sympathetic activity of adolescents with hypertension.