Analysis of Heart Period and Arterial Pressure Variability in Childhood Hypertension

Pathophysiology of primary hypertension in children and adolescents

The progress in research on the physiology of the cardiovascular system made in the last 100 years allowed for the development of the pathogenesis not only of secondary forms of hypertension but also of primary hypertension. The main determinants of blood pressure are described by the relationship between stroke volume, heart rate, peripheral resistance, and arterial stiffness. The theories developed by Guyton and Folkow describe the importance of the volume factor and total peripheral resistance. However, none of them fully presents the pathogenesis of essential hypertension. The multifactorial model of primary hypertension pathogenesis developed by Irving Page in the 1940s, called Page's mosaic, covers most of the pathophysiological phenomena observed in essential hypertension. The most important pathophysiological phenomena included in Page's mosaic form a network of interconnected "nodes". New discoveries both from experimental and clinical studies made in recent decades have allowed the original Page mosaic to be modified and the addition of new pathophysiological nodes. Most of the clinical studies confirming the validity of the multifactorial pathogenesis of primary hypertension concern adults. However, hypertension develops in childhood and is even perinatally programmed. Therefore, the next nodes in Page's mosaic should be age and perinatal factors. This article presents data from pediatric clinical trials describing the most important pathophysiological processes associated with the development of essential hypertension in children and adolescents.

No Increase in Masked Hypertension Prevalence in Children With Sickle Cell Disease in France

BACKGROUND

An important prevalence (32%-45%) of masked hypertension has been reported in children with sickle cell disease (SCD). Stroke screening is well established using transcranial Doppler (TCD) ultrasound. The objectives of our proof-of-concept study in childhood SCD were to evaluate the prevalence of hypertension and its relationships with cerebral vasculopathy (TCD velocity) and to further evaluate in a subgroup of children the correlations of cardiovascular autonomic nervous system indices with TCD velocity.

METHODS

Ambulatory blood pressure measurement (ABPM) and TCD velocity were obtained in children with SCD and in a restricted sample, cardiac sympathovagal balance using heart rate variability analyses, baroreflex sensitivity, and pulse wave velocity were measured.

RESULTS

In 41 children with SCD (median age 14.0 years, 19 girls, SS/Sβ + thalassemia/SC: 33/2/6), ABPM results showed masked hypertension in 2/41 (5%, 95% confidence interval, 0-11) children, consistent with the prevalence in the general pediatric population, elevated blood pressure (BP) in 4/41 (10%) children, and a lack of a normal nocturnal dip in 19/41 children (46%). Children with increased TCD velocity had lower nocturnal dipping of systolic BP. In the 10 participants with extensive cardiovascular assessment, increased TCD velocity was associated with parasympathetic withdrawal and baroreflex failure. Exaggerated orthostatic pressor response or orthostatic hypertension was observed in 7/10 children that was linked to parasympathetic withdrawal.

CONCLUSIONS

Autonomic nervous system dysfunction, namely loss of parasympathetic modulation, of SCD contributes to increase TCD velocity but is not associated with an increased prevalence of masked hypertension.

CLINICAL TRIALS REGISTRATION

NCT04911049.

Vitamin D Deficiency in Children With Vasovagal Syncope Is Associated With Impaired Circadian Rhythm of Blood Pressure

BACKGROUND

Vitamin D deficiency is associated with the risk of cardiovascular diseases. We aimed to investigate the serum vitamin D levels in children with vasovagal syncope (VVS) and explore the correlation of vitamin D status and circadian rhythm of blood pressure in VVS pediatric patients.

METHODS

This was a retrospective study. 130 syncopal children diagnosed with VVS were included in the study. 110 age and gender matched healthy individuals were enrolled as control. According to serum 25(OH)D levels, VVS patients were divided into vitamin D sufficient group and vitamin D deficient group. Detailed information of VVS children with vitamin D deficiency and sufficiency on demographic data, baseline laboratory testing, echocardiogram, ambulatory blood pressure monitoring, and Holter ECG recording were extracted and analyzed.

RESULTS

VVS children had a higher prevalence of vitamin D deficiency compared with healthy individuals (33.8% vs. 20.0%, P = 0.017). VVS patients with vitamin D deficiency had a higher rate of non-dipper blood pressure (79.5% vs. 59.3%, P = 0.021) and a lower value of square root of mean squared differences of successive normal to normal intervals (rMSSD) (median 107.8 vs. 141.0 ms, P = 0.035) compared with those with vitamin D sufficiency. Logistic regression analysis showed that non-dipper blood pressure was associated with serum 25(OH)D level [OR = 0.979, 95% CI (0.960, 0.999), P = 0.036].

CONCLUSION

VVS pediatric patients had a higher prevalence of vitamin D deficiency. VVS children with vitamin D deficiency showed a higher rate of non-dipper blood pressure, suggesting that vitamin D deficiency is correlated with impaired circadian rhythm of blood pressure.

Salt and Sugar: Two Enemies of Healthy Blood Pressure in Children

The prevalence of essential arterial hypertension in children and adolescents has grown considerably in the last few decades, making this disease a major clinical problem in the pediatric age. The pathogenesis of arterial hypertension is multifactorial, with one of the components being represented by incorrect eating habits. In particular, excessive salt and sugar intake can contribute to the onset of hypertension in children, particularly in subjects with excess weight. Babies have an innate predisposition for sweet taste, while that for salty taste manifests after a few weeks. The recent modification of dietary styles and the current very wide availability of salt and sugar has led to an exponential increase in the consumption of these two nutrients. The dietary intake of salt and sugar in children is in fact much higher than that recommended by health agencies. The purpose of this review is to explore the mechanisms via which an excessive dietary intake of salt and sugar can contribute to the onset of arterial hypertension in children and to show the most important clinical studies that demonstrate the association between these two nutrients and arterial hypertension in pediatric age. Correct eating habits are essential for the prevention and nondrug treatment of essential hypertension in children and adolescents.

Exercise-associated prevention of adult cardiovascular disease in children and adolescents: monocytes, molecular mechanisms, and a call for discovery

Atherosclerosis originates in childhood and adolescence. The goal of this review is to highlight how exercise and physical activity during childhood and adolescence, critical periods of growth and development, can prevent adult cardiovascular disease (CVD), particularly through molecular mechanisms of monocytes, a key cell of the innate immune system. Monocytes are heterogeneous and pluripotential cells that can, paradoxically, play a role in both the instigation and prevention of atherosclerosis. Recent discoveries in young adults reveal that brief exercise affects monocyte gene pathways promoting a cell phenotype that patrols the vascular system and repairs injuries. Concurrently, exercise inhibits pro-inflammatory monocytes, cells that contribute to vascular damage and plaque formation. Because CVD is typically asymptomatic in youth, minimally invasive techniques must be honed to study the subtle anatomic and physiologic evidence of vascular dysfunction. Exercise gas exchange and heart rate measures can be combined with ultrasound assessments of vascular anatomy and reactivity, and near-infrared spectroscopy to quantify impaired O2 transport that is often hidden at rest. Combined with functional, transcriptomic, and epigenetic monocyte expression and measures of monocyte-endothelium interaction, molecular mechanisms of early CVD can be formulated, and then translated into effective physical activity-based strategies in youth to prevent adult-onset CVD.

The role of blood pressure, body weight and fat distribution on left ventricular mass, diastolic function and cardiac geometry in children

BACKGROUND

Hypertension and obesity in childhood are related to early cardiac damage, as left ventricular hypertrophy. Few studies have analyzed the independent effects of hypertension and weight excess on diastolic function and left ventricular geometry.

OBJECTIVE

We studied the effects of weight, waist circumference (as an index of fat distribution) and blood pressure on left ventricular mass index, the risk of left ventricular hypertrophy, diastolic function and left ventricular geometry in 526 children (237 girls, age range 6-15 years).

METHODS

Children were divided into normotensive, prehypertensive and hypertensive (US Nomograms) groups, and into normal-weight, overweight, and obese (International Obesity Task Force classification) groups. Left ventricular mass index, diastolic function and left ventricular geometry were assessed.

RESULTS

SBP z-scores and blood pressure categories significantly influenced cardiac mass (P < 0.001 and P = 0.02, respectively) and the prevalence of left ventricular hypertrophy (P < 0.001 and P < 0.05, respectively). Obesity, BMI, and waist circumference z-scores were significantly associated with an increment in E/Em ratio (P < 0.001, P < 0.01, and P < 0.01, respectively). Increasing blood pressure values and the presence of prehypertension (P < 0.05) and hypertension (P < 0.003), but not weight excess, were associated with concentric cardiac remodeling. In contrast, concentric hypertrophy was associated with hypertension (P < 0.01), obesity (P < 0.001), and increasing waist circumference (P < 001).

CONCLUSIONS

Blood pressure values and hypertension are independently associated with an increase of cardiac mass and the presence of cardiac hypertrophy. Obesity and waist circumference, but not hypertension, are associated with a worsening of diastolic function, whereas only hypertensive children show high prevalence of concentric remodeling. Blood pressure and body weight and fat distribution have an independent and different impact on left ventricular structure and function in children.

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.

Heart rate variability and cardiovascular risk factors in adolescent boys

OBJECTIVE

To establish reference values of heart rate variability (HRV) measures in a cohort of adolescent boys and to determine the relationship between HRV and the clustering of risk factors (RFs) for cardiovascular disease.

STUDY DESIGN

This cross-sectional study included 1152 adolescent boys (age: 16.6 ± 1.2 years old). Demographic data, health-related habits, obesity indicators, and blood pressure were evaluated. HRV measures of time (SD of all RR intervals, root mean square of the squared differences between adjacent normal RR intervals, and the percentage of adjacent intervals over 50 ms) and frequency domains were assessed (low [LF] and high [HF] frequency).

RESULTS

The components of HRV were RR interval (827 ± 128 ms), SD of all RR intervals (61.9 ± 23.5 ms), root mean square of the squared differences between adjacent normal RR intervals (54.5 ± 29.4 ms), percentage of adjacent intervals over 50 ms (29.4 ± 20.4%), LF (53 ± 16 nu), HF (47 ± 16), and LF/HF (1.44 ± 1.08). Greater sympathetic and lower parasympathetic modulation at rest were associated with higher adiposity, higher blood pressure and physical inactivity. Adolescents with 2 or more RFs also presented lower HRV than subjects with no RFs (P < .001).

CONCLUSIONS

The study has provided descriptive indicators that help the interpretation of HRV results in adolescents. Lower HRV measures are associated with the clustering of cardiovascular RFs.

Poincaré plot width, morning urine norepinephrine levels, and autonomic imbalance in children with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) in childhood is accompanied by sympathetic overflow unopposed by the parasympathetic tone. Complex methods like power spectral analysis of heart rate variability have been applied to study this imbalance. In this report, width of Poincaré scattergram of the R-R interval (parasympathetic tone) and morning urine norepinephrine concentration (sympathetic activity) were used to assess autonomic imbalance.

METHODS

Poincaré plot was obtained from the electrocardiographic channel of nocturnal polysomnography and its width was measured, and norepinephrine-to-creatinine concentration ratio was calculated in morning urine specimen.

RESULTS

Twenty children with obstructive sleep apnea and moderate-to-severe nocturnal hypoxemia (oxygen saturation of hemoglobin [SpO(2)] nadir <90%), 24 subjects with mild hypoxemia (SpO(2) nadir ≥90%), and 11 control subjects were recruited. Children with obstructive sleep apnea and moderate-to-severe hypoxemia had significantly narrower Poincaré plot width (318.7 ± 139.3 ms) and higher ln-transformed urine norepinephrine-to-creatinine ratio (4.5 ± 0.6) than control subjects (484.2 ± 104.4 ms and 3.8 ± 0.4, respectively; P < 0.05). Ln-transformed urine norepinephrine levels were inversely related to Poincaré plot width (P = 0.02).

CONCLUSIONS

Subjects with obstructive sleep apnea and moderate-to-severe nocturnal hypoxemia have enhanced sympathetic activity and reduced parasympathetic drive. Poincaré plot width and urine norepinephrine levels are simple measures of autonomic imbalance in pediatric obstructive sleep apnea.

Impaired blood pressure control in children with obstructive sleep apnea

BACKGROUND

Obstructive sleep apnea (OSA) in adults has been associated with hypertension, low baroreflex sensitivity (BRS), a delayed heart rate response to changing blood pressure (heart period delay [HPD]), and increased blood pressure variability (BPV). Poor BRS may contribute to hypertension by impairing the control of blood pressure (BP), with increased BPV and HPD. Although children with OSA have elevated BP, there are scant data on BRS, BPV, or HPD in this group.

METHODS

105 children ages 7-12 years referred for assessment of OSA and 36 nonsnoring controls were studied. Overnight polysomnography (PSG) was performed with continuous BP monitoring. Subjects were assigned to groups according to their obstructive apnea-hypopnea index (OAHI): primary snoring (PS) (OAHI ≤1event/h), mild OSA (OAHI>1- ≤5events/h) and moderate/severe (MS) OSA (OAHI>5events/h). BRS and HPD were calculated using cross spectral analysis and BPV using power spectral analysis.

RESULTS

Subjects with OSA had significantly lower BRS (p<.05 for both) and a longer HPD (PS and MS OSA, p<.01; mild OSA, p<.05) response to spontaneous BP changes compared with controls. In all frequencies of BPV, the MS group had higher power compared with the control and PS groups (low frequency [LF], p<.05; high frequency [HF], p<.001).

CONCLUSIONS

Our study demonstrates reduced BRS, longer HPD, and increased BPV in subjects with OSA compared to controls. This finding suggests that children with OSA have altered baroreflex function. Longitudinal studies are required to ascertain if this dampening of the normal baroreflex response can be reversed with treatment.

Exercise might improve cardiovascular autonomic regulation in adolescents with type 1 diabetes

Considering that changes in exercise routines might have relevance in treatment of adolescents with type 1 diabetes mellitus, we sought to assess whether spontaneous modifications to weekly exercise habits might occur in these patients and whether such variations would be accompanied by alterations in autonomic profile. In this observational study, we examined 77 patients (age 15.0 ± 0.6 years.) who in addition to a tailored optimal insulin treatment were invited to perform at least 1 h a day of moderate, aerobic exercise, as suggested by recent guidelines. Patients were studied at baseline (T0) and after 15.8 ± 0.7 months (T1). They were divided into three subgroups according to increased, unchanged and diminished total estimated weekly METs between T0 and T1. Autonomic profile was evaluated by assessing spontaneous baroreflex gain and low-frequency oscillation in arterial pressure, using spectral analysis of RR and systolic arterial pressure time series. Insulin therapy and biochemical data were similar among the 3 groups at T0 and T1, while body mass index standard deviation score was slightly reduced (p < 0.04) and markers of autonomic performance were improved (alpha index, from 17 ± 1 to 20 ± 2 ms/mmHg, p < 0.002) in the group who increased the amount of exercise (from 1627 ± 250 to 3582 ± 448 METs min wt(-1), p < 0.001). Furthermore, the change in total weekly METs significantly correlates with changes of key indices of autonomic regulation. The favourable autonomic effects of moderate increase in spontaneous exercise load suggest testing more formally this intervention in adolescents with type 1 diabetes.

Focus on prevention, diagnosis and treatment of hypertension in children and adolescents

The European Society of Hypertension has recently published its recommendations on prevention, diagnosis and treatment of high blood pressure in children and adolescents. Taking this contribution as a starting point the Study Group of Hypertension of the Italian Society of Pediatrics together with the Italian Society of Hypertension has conducted a reappraisal of the most recent literature on this subject. The present review does not claim to be an exhaustive description of hypertension in the pediatric population but intends to provide Pediatricians with practical and updated indications in order to guide them in this often unappreciated problem.

This document pays particular attention to the primary hypertension which represents a growing problem in children and adolescents. Subjects at elevated risk of hypertension are those overweight, with low birth weight and presenting a family history of hypertension. However, also children who do not present these risk factors may have elevated blood pressure levels. In pediatric age diagnosis of hypertension or high normal blood pressure is made with repeated office blood pressure measurements that show values exceeding the reference values. Blood pressure should be monitored at least once a year with adequate methods and instrumentation and the observed values have to be interpreted according to the most updated nomograms that are adjusted for children’s gender, age and height. Currently other available methods such as ambulatory blood pressure monitoring and home blood pressure measurement are not yet adequately validated for use as diagnostic instruments. To diagnose primary hypertension it is necessary to exclude secondary forms. The probability of facing a secondary form of hypertension is inversely proportional to the child’s age and directly proportional to blood pressure levels. Medical history, clinical data and blood tests may guide the differential diagnosis of primary versus secondary forms. The prevention of high blood pressure is based on correct lifestyle and nutrition, starting from childhood age. The treatment of primary hypertension in children is almost exclusively dietary/behavioral and includes: a) reduction of overweight whenever present b) reduction of dietary sodium intake c) increase in physical activity. Pharmacological therapy will be needed rarely and only in specific cases.

Gender-specific prevalence and associated risk factors of prehypertension among rural children and adolescents in Northeast China: a cross-sectional study

Little is known about the prevalence and risk profile of prehypertension among Chinese children and adolescents. The aim of the present study was to investigate the prehypertensive status and its associated risk factors among rural Chinese children and adolescents. We conducted a cross-sectional study including 5,245 children and adolescents (2,732 boys and 2,513 girls) aged 5-18 years in Northeast China. Main anthropometric data and related information were collected. The overall prevalence of prehypertension and hypertension was 15 % and 20.2 %, respectively. The prevalence of prehypertension among boys was 15.7 %, compared to that of 14.2 % among girls (P = 0.256). After adjusting for age, race, weight status, waist circumference, triceps skinfold, family income, smoking and drinking status, boys aged 12-14 and 15-18 years had a 2.86- and 5.97-fold risk of prehypertension, respectively, compared to those aged 5-8 years. Overweight and obese boys had an increased risk of prehypertension in comparison to those with normal weight (overweight: odds ratio [OR] = 1.837, 95 % confidence interval [CI] 1.321-2.556; obese: OR = 2.941, 95 % CI 1.783-4.851). A larger triceps skinfold (≥90th percentile) was significantly related to increased odds of prehypertension (OR = 2.32; 95 % CI, 1.516-3.55) among boys. For girls, only older age was found to be a risk factor for prehypertension.

CONCLUSION

Pediatric prehypertension is highly prevalent in rural Northeast China. The risk factors for prehypertension differed among boys and girls. A more comprehensive risk profile of prehypertension among children and adolescents needs to be established for early prevention.

Baroreflex sensitivity after adenotonsillectomy in children with obstructive sleep apnea during wakefulness and sleep

STUDY OBJECTIVES

Children with obstructive sleep apnea have blunted baroreflex sensitivity and increased blood pressure variability. The aim of the study was to test the hypothesis that treatment of sleep apnea by adenotonsillectomy results in significant improvement of baroreflex sensitivity, lowering of blood pressure and blood pressure variability and increase vagal heart rate modulation.

STUDY DESIGN

One hundred ninety-four children aged 9.6 ± 2.3 years were enrolled; 133 had obstructive sleep apnea and 61 were healthy controls. For children with sleep apnea, polysomnography with 3-lead electrocardiography and continuous blood pressure was performed before adenotonsillectomy, then 6 weeks and 6 months postoperatively. Controls underwent the same assessment at study entry and 6 months later. Spontaneous baroreflex sensitivity was measured in the time and frequency domains. Data analyses were performed for available and complete cases.

RESULTS

Children with sleep apnea experienced postoperatively an increase in baroreflex sensitivity and decrease in blood pressure variability during wakefulness and sleep. A decrease in blood pressure during sleep and in heart rate during wakefulness was also measured. The improvement in baroreflex sensitivity was predicted by the change in the apnea-hypopnea and arousal indices. A normal pattern of rising baroreflex sensitivity during the night was restored in children with severe apnea after surgery. However, baroreceptor sensitivity did not completely normalize after treatment.

CONCLUSION

Treatment of obstructive sleep apnea in children by adenotonsillectomy is associated with gradual improvement in known risk factors for cardiovascular disease. Complete normalization of baroreceptor sensitivity was not achieved 6 months postoperatively.

Baroreflex sensitivity is associated with sleep-related breathing problems in adolescents

OBJECTIVES

To examine the relationship between sleep-related breathing problems (SRBPs) and baroreflex sensitivity (BRS) among adolescents and assesses whether body mass influences this relationship.

STUDY DESIGN

SRBPs were assessed in 106 adolescents aged 11-14 years using the Pediatric Sleep Questionnaire. Body mass index (BMI) was calculated, and 5 minutes of continuous beat-to-beat blood pressure (Finapres) and R-R interval were recorded (standard electrocardiogram) after 15 minutes of supine rest. Spectral indices were computed using fast Fourier transform, and transfer function analysis was used to compute BRS.

RESULTS

Regression analyses indicate an interaction between BMI and SRBPs (b=-.151, P=.015) on BRS. Graphing the interaction showed that those with higher SRBP scores had lower BRS but that this effect was stronger for those with higher BMI.

CONCLUSIONS

Adolescents with elevated SRBP scores had lower BRS. In addition, higher BMI amplified the risk of higher SRBP scores on BRS.

The association between baroreflex sensitivity and blood pressure in children

Low baroreflex sensitivity (BRS) and heart rate variability (HRV) are associated with the pathogenesis of adult hypertension. However, limited information exists about the negative consequences of elevated childhood blood pressure (BP) and autonomic regulation. Additionally, there are developmental changes in autonomic regulation throughout puberty, yet studies have not appropriately accounted for this. The objective of this study was to investigate BRS and HRV in children with 2 different BP profiles, while controlling for the effects of maturation, age, sex, and body composition. A sample of 11- to 14-year-old participants were divided into 2 BP groups: high BP (HBP; ≥95th percentile; n = 21) and normal BP (NBP; <90th percentile; n = 85). Automated BP was measured at 2 time points. In lab-based testing, 5 min of beat-to-beat BP (Finapres) and R-R interval (RRI) were recorded (standard electrocardiogram) after 15 min of supine rest. Spectral indices were computed using fast Fourier transform, and transfer function analysis was used to compute BRS. High frequency (HF) and low frequency (LF) power spectral areas were set to 0.15-0.4 Hz and 0.04-0.15 Hz, respectively, and BRS was determined for the LF area. After adjustment for age, sex, maturation, and body composition, BRS (p = 0.04), LF (p = 0.008), and HF (p = 0.01) RRI variability, and RRI total power (p = 0.005) were lower in the HBP than in the NBP participants. As well, the LF/HF systolic BP variability ratio was higher in the HBP than in the NBP group (p = 0.03). Despite their young age, these children with high, yet not clinically hypertensive BP, display reduced autonomic regulation.

Prehypertension in children and adolescents: association with body weight and neck circumference

OBJECTIVE

The present study was undertaken to investigate the role of neck circumference (NC) in predicting prehypertension in children and adolescents.

METHODS

We conducted a cross-sectional study including 6,802 children and adolescents (3,631 boys and 3,171 girls) aged 5-18 years. Main anthropometric data and related information were collected.

RESULTS

The prevalence of prehypertension was 14.4%, 16.4% and 17.1% in normal weight, overweight and obese group respectively. Among the participants with normal body mass index (BMI), higher NC was significantly associated with increased odds of prehypertension (OR: 1.439; 95% CI: 1.118 to 1.853) after adjustment for age, gender, BMI and WC. Significant associations between NC and either systolic blood pressure (SBP) (β=0.581 mmHg) or diastolic blood pressure (DBP) (β=0.236 mmHg) were found in the linear regression. No significant ORs were observed either in overweight or in obese categories.

CONCLUSION

We concluded that additional measure of NC might expand the ability of BMI for the identification of prehypertension in normal weight children and adolescents.

Relationship of aortic pulse wave velocity and baroreceptor reflex sensitivity to blood pressure control in patients with repaired coarctation of the aorta

BACKGROUND

Increased aortic stiffness and reduced baroreceptor reflex sensitivity have been described independently after coarctation of the aorta (CoA) repair. This study sought to determine the relationship between these variables and blood pressure control in adolescents after early CoA repair.

METHODS

Spontaneous baroreceptor reflex sensitivity (sBRS) and aortic pulse wave velocity (PWV) were measured in 29 adolescents after CoA repair and compared with 20 age-matched controls. Patients treated for hypertension or having residual aortic narrowing were excluded. Ambulatory blood pressure (ABP), heart rate variability, and cardiac output were also recorded. After ABP measurement, CoA subjects were classified as normotensive or hypertensive.

RESULTS

Nine patients (31%) were hypertensive according to standard definitions, and this subgroup had higher aortic PWV than the normotensive subgroup (P = .004). There was a significant positive correlation between ABP and PWV seen in the whole CoA group (r(2) = 0.5, P < .01). The normotensive subgroup had increased sBRS compared with controls (P = .02). This difference was not seen between the hypertensive subgroup and controls. There was a significant inverse relationship between sBRS and aortic PWV in the whole CoA group (r(2) = 0.25, P = .01). The normotensive subgroup had a significant reduction in stroke index compared with controls (P = .02), which was not seen in the hypertensive subgroup (P = .96).

CONCLUSIONS

Adolescents with hypertension after CoA repair have increased aortic PWV and a relative reduction in sBRS compared with normotensive CoA patients. Thus, failure of the baroreceptor reflex to compensate for increasing arterial stiffness may herald the onset of hypertension in these patients.

Hypertension, prehypertension, and transient elevated blood pressure in children: association with weight excess and waist circumference

BACKGROUND

To assess the prevalence of hypertension (H), prehypertension (PH), and transient elevated blood pressure (TH) and their relationship with weight class and waist circumference (WC) in an unselected population of Northern Italian children.

METHODS

A cross-sectional study was conducted in 5,131 children (5-11 years). Weight class was defined according to the International Obesity Task Force references, H and PH according to the National High Blood Pressure Education Program. A child was classified as having PH or H when systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) at first screening were > or =90th percentile and the mean of three subsequent measures was between the 90th and 95th or > or =95th percentile, respectively. When BP values at the first screening were > or =90th percentile but the mean of three subsequent measures was <90th percentile the child was classified as having TH.

RESULTS

A proportion of 3.4% presented H, 2.7% PH, and 10.4% TH, 20% overweight, and 6% obesity. Weight class and WC were significantly associated to an increased risk of falling into any of the hypertensive categories. In children with TH BP z-scores of the mean of the three subsequent measurements following the first screening were significantly higher than BP z-scores observed in normotensive children (P value <0.001).

CONCLUSIONS

Weight class and WC are associated with BP. This is observed not only for H but also for PH, and for nonsustained forms of H. Prospective studies are needed to assess whether children with PH and TH will develop sustained H.

Prolonged head down bed rest-induced inactivity impairs tonic autonomic regulation while sparing oscillatory cardiovascular rhythms in healthy humans

BACKGROUND

Physical inactivity represents a major risk for cardiovascular disorders, such as hypertension, myocardial infarction or sudden death; however, underlying mechanisms are not clearly elucidated. Clinical and epidemiological investigations suggest, beyond molecular changes, the possibility of an induced impairment in autonomic cardiovascular regulation. However, this hypothesis has not been tested directly.

METHODS

Accordingly, we planned a study with noninvasive, minimally intrusive, techniques on healthy volunteers. Participants were maintained for 90 days strictly in bed, 24 h a day, in head-down (-6 degrees ) position (HDBR). Physical activity was thus virtually abolished for the entire period of HDBR. We examined efferent muscle sympathetic nerve activity, as a measure of vascular sympathetic control, baroreceptor reflex sensitivity, heart rate variability (assessing cardiovagal regulation), RR and systolic arterial pressure and low-frequency and high-frequency normalized components (as a window on central oscillatory regulation). Measures were obtained at rest and during simple maneuvers (moderate handgrip, lower body negative pressure and active standing) to assess potential changes in autonomic cardiovascular responsiveness to standard stimuli and the related oscillatory profiles.

RESULTS

HDBR transiently reduced muscle sympathetic nerve activity, RR, heart rate variability and baroreceptor reflex sensitivity late during HDBR or early during the recovery phase. Conversely, oscillatory profiles of RR and systolic arterial pressure variability were maintained throughout. Responsiveness to test stimuli was also largely maintained.

CONCLUSION

Prolonged inactivity as induced by HDBR in healthy volunteers reduces both cardiovagal and vascular sympathetic regulation, while largely maintaining peripheral responsiveness to standardized stimuli and sparing the functional structure of central oscillatory cardiovascular regulation.

Baroreflex gain in children with obstructive sleep apnea

RATIONALE

We previously demonstrated that children with obstructive sleep apnea have increased blood pressure associated with changes in left ventricular mass index. Others have shown in adults that blood pressure variability is an important predictor of changes in left ventricular mass. The baroreflex system buffers blood pressure changes by varying heart rate. We have thus hypothesized that (1) baroreflex system gain is increased during sleep, improving blood pressure buffering; (2) children with obstructive sleep apnea lack this baroreflex gain increase; and (3) reduced blood pressure buffering results in exaggerated blood pressure variability that is associated with end-organ damage.

OBJECTIVES

Compare measures of left ventricular mass index and nighttime baroreflex gain of healthy children to those of children with obstructive sleep apnea.

METHODS

A total of 169 children (50 control subjects, 63 with mild obstructive sleep apnea, and 56 with severe obstructive sleep apnea) with a mean age of 9.9 years (+/-2.2) underwent echocardiography followed by polysomnography with continuous blood pressure measurement. Baroreflex gain was calculated in time and frequency domains.

MEASUREMENTS AND MAIN RESULTS

Healthy children demonstrated a nighttime pattern of increasing baroreflex gain. Children with obstructive sleep apnea had decreased nighttime baroreflex gain compared with control subjects. Nighttime blood pressure and blood pressure variability were significantly correlated with left ventricular mass index.

CONCLUSIONS

Obstructive sleep apnea is associated with a decrease in nighttime baroreflex gain and an increase in blood pressure variability. This increase is correlated with changes in left ventricular mass index.