Correlates of the hemodynamic determinants of blood pressure

Fat-free mass may play a dominant role in the association between systolic blood pressure and body composition in children and adolescents

Systolic blood pressure (SBP) is significantly associated with body composition in children and adolescents. However, which one of the components of body composition is the dominant contributor to SBP in children and adolescents remains unclear. We, therefore, aimed to determine the dominant contributor to SBP among components of body composition in a large cohort of American children and adolescents derived from the National Health and Nutrition Examination Survey with cross-sectional analysis. In total, 13 618 children and adolescents (median age 13 years; 6107 girls) with available data on whole-body dual-emission X-ray absorptiometry measurements were included. Multiple linear regression showed that SBP was associated with higher total fat-free mass in boys (β = 0·49, P < 0·001) and girls (β = 0·47, P < 0·001) and with higher total fat mass only in boys (β = 0·12, P < 0·001) after adjustment for covariates. When taking fat distribution into consideration, SBP was associated with higher trunk fat mass (boys: β = 0·28, P < 0·001; girls: β = 0·15, P < 0·001) but negatively associated with leg fat mass (Boys: β = -0·14, P < 0·001; Girls: β = -0·11, P < 0·001), in both boys and girls. Dominance analysis showed that total fat-free mass was the dominant contributor to SBP (boys: 49 %; girls: 55·3 %), followed by trunk fat mass (boys: 32·1 %; girls: 26·9 %); leg fat mass contributed the least to SBP in boys (18·9 %) and girls (17·8 %). Our findings indicated that total fat-free mass was not only associated with SBP but also the most dominant contributor to SBP variation in American children and adolescents.

Role of muscle mass in the association between handgrip strength and blood pressure in children and adolescents

Studies have reported conflicting results on the association between handgrip strength (HGS) and blood pressure during childhood and adolescence. High multicollinearity involving somatic components that influence both HGS and blood pressure might be an important source of bias. This study sought to investigate the independent effects of HGS and muscle mass on blood pressure levels in children and adolescents. Muscle mass and fat mass (Multifrequency Electrical Bioimpedance) and systolic (SBP) and diastolic (DBP) blood pressure (Automatic oscillometric device) were assessed in 833 volunteers aged 6-18 years, of both sexes. Handgrip strength-for-age quartiles were calculated and participants were assigned to groups by HGS quartiles. Analysis of covariance was conducted to address the linear association between HGS and SBP adjusted for height, muscle mass, and fat mass. To test for linear trend, contrast analysis was conducted. Partial eta-squared was used to confirm or rule out a small significant effect of the independent variables on SBP. The effect size of HGS on SBP was not significant in both sexes. In girls, 1.7% of the between-groups variance in SBP was accounted for by muscle mass (P = 0.016). In boys, 2.3% and 1.8% of the between-groups variance in SBP was accounted for by muscle mass (P = 0.001) and height (P = 0.005), respectively. In conclusion, children with a more advanced physical maturity for their age, that is, who are taller, stronger, and have greater fat-free mass, may be nearly reaching the physiological parameters of adulthood, and consequently have higher systolic blood pressure.

Alterations to Kidney Physiology during Cardiopulmonary Bypass-A Narrative Review of the Literature and Practical Remarks

INTRODUCTION

According to different authors, cardiac surgery-associated acute kidney injury (CSA-AKI) incidence can be as high as 20-50%. This complication increases postoperative morbidity and mortality and impairs long-term kidney function in some patients. This review aims to summarize current knowledge regarding alterations to renal physiology during cardiopulmonary bypass (CPB) and to discuss possible nephroprotective strategies for cardiac surgeries. Relevant sections: Systemic and renal circulation, Vasoactive drugs, Fluid balance and Osmotic regulation and Inflammatory response.

CONCLUSIONS

Considering the available scientific evidence, it is concluded that adequate kidney perfusion and fluid balance are the most critical factors determining postoperative kidney function. By adequate perfusion, one should understand perfusion with proper oxygen delivery and sufficient perfusion pressure. Maintaining the fluid balance is imperative for a normal kidney filtration process, which is essential for preserving the intra- and postoperative kidney function.

FUTURE DIRECTIONS

The review of the available literature regarding kidney function during cardiac surgery revealed a need for a more holistic approach to this subject.

The impact of body composition and fat distribution on blood pressure in young and middle-aged adults

Background

The relative contributions of each component of body composition to blood pressure (BP) remain unclear.

Objective

We aimed to comprehensively investigate the impact of body composition and fat distribution on BP and quantify their relative contributions to BP in a large cohort with young and middle-aged adults.

Methods

14,412 participants with available data on whole-body DXA measurement from the National Health and Nutrition Examination Survey were included. Multiple stepwise linear regressions of BP on components of body composition and fat distribution were built. Then, relative importance analysis was performed to quantify the contributions of each component to BP.

Results

The median age of participants was 36 years and there were 50.7% women. Linear regression with mutual adjustment showed that total fat mass, total muscle mass, and trunk fat mass significantly and positively associated with BP; however, arm and leg fat mass significantly and negatively associated with BP. In men, after further adjusted for potential covariates, SBP were significantly determined by trunk fat mass (β = 0.33, P < 0.001), leg fat mass (β = − 0.12, P < 0.001), and total muscle mass (β = 0.10, P < 0.001); and DBP were significantly determined by trunk fat mass (β = 0.52, P < 0.001), leg fat mass (β = −0.15, P < 0.001), arm fat mass (β = −0.23, P < 0.001), and total muscle mass (β = 0.06, P < 0.001). Similar results were observed in women. Relative importance analysis showed that trunk fat mass was the major contributor (38–61%) to both SBP and DBP; meanwhile, total muscle mass also made relatively great contribution (35–43%) to SBP.

Conclusion

Both fat mass and muscle mass independently associated with and substantially contributed to SBP in both men and women. After full adjustment, trunk fat mass positively associated with both SBP and DBP, and was the most dominant contributor to BP; however, leg fat mass negatively associated with both SBP and DBP.

Haemodynamics of Hypertension in Children

PURPOSE OF REVIEW

To review the haemodynamic characteristics of paediatric hypertension.

RECENT FINDINGS

Pulsatile components of blood pressure are determined by left ventricular dynamics, aortic stiffness, systemic vascular resistance and wave propagation phenomena. Recent studies delineating these factors have identified haemodynamic mechanisms contributing to primary hypertension in children. Studies to date suggest a role of cardiac over activity, characterized by increased heart rate and left ventricular ejection, and increased aortic stiffness as the main haemodynamic determinants of primary hypertension in children.

Muscle mass is the main somatic growth indicator associated with increasing blood pressure with age in children and adolescents

Studies have shown that lean mass must be an important determinant of blood pressure value in children and adolescents. The absence of adjustment for the collinearity between lean and fat mass (FM), restricted age span, and lack of separate analysis by sex leave a gap in the literature. This study determined direct and indirect effects of the somatic growth indicators linked to the association between age and systolic blood pressure (SBP) in boys and girls. This is a cross-sectional study comprising 1,510 participants (6-18 years). Path analysis was used to test a model in which the association between age and SBP would have a direct and independent component, but also indirect mediating paths through muscle mass (MM), FM, and height. There was no significant association between age and SBP (unstandardized β ± SE) for both girls (0.072 ± 0.236, P = .761) and boys (0.238 ± 0.264, P = .368). Height was not a mediator for the association between age and SBP in both girls (-0.291 ± 0.156, P = .062) and boys (-0.015 ± 0.187, P = .935). Mediating effect of MM was significant for both girls (0.909 ± 0.137, P < .001) and boys (1.341 ± 0.161, P < .001), whereas mediating path through FM was significant only for boys (0.069 ± 0.023, P = .003). In conclusion, muscle mass was the strongest somatic growth indicator associated with the blood pressure value in children and adolescents. Further increase in body fat mass may affect systolic blood pressure more in boys than in girls.

Recommendations for exercise and screening for safe athletic participation in hypertensive youth

Physical activity is an important component of ideal cardiovascular health. Current guidelines recommend that youth with hypertension participate in competitive sports once hypertensive target organ effects and risks have been assessed and that children with hypertension receive treatment to lower BP below stage 2 thresholds (e.g., < 140/90 mmHg or < 95th percentile + 12 mmHg) before participating in competitive sports. Despite these recommendations, pediatricians and pediatric subspecialists continue to struggle with how best to counsel their patients regarding appropriate forms of physical activity, the impact of exercise on blood pressure, and how best to screen for cardiovascular conditions that place youth at risk for sudden cardiac death. This review provides a summary of our current knowledge regarding the safety and utility of exercise in the management of high blood pressure in youth. We review determinants of blood pressure during exercise, the impact of blood pressure on cardiovascular health and structure, mechanisms for assessing cardiometabolic fitness (e.g., exercise stress test), contraindications to athletic participation, and how best to plan for athletic participation among hypertensive youth. Greater knowledge in these areas may offer clarity to providers faced with the challenge of prescribing exercise recommendations for hypertensive youth.

Metabolic implications of low muscle mass in the pediatric population: a critical review

Skeletal muscle is recognized as a tissue with high metabolic capacity given its key roles in glucose and lipid metabolism. Although low muscle mass has been associated with metabolic disorders in adults, it is not clear if this body composition phenotype is related to metabolic health status earlier in life. In this review, we aim to clarify whether having low muscle mass is associated with increased risk of metabolic dysregulation in the pediatric population. Fifteen original articles investigating the relationship between body composition measures of muscle mass and single or clustered metabolic risk factors in children and adolescents were critically evaluated. Despite a growing body of evidence supporting low muscle mass as a risk factor for metabolic health in children and adolescents, conflicting associations were reported. Differences in body composition techniques, muscle mass indices, and clinical methods used to assess metabolic biomarkers may have contributed to a lack of a consistent conclusion. Moreover, most studies did not control for potential biological and lifestyle confounders. Future studies using precise, reproducible techniques to evaluate body composition and metabolic biomarkers are required to determine the implications of low muscle mass on metabolic health during childhood and adolescence.

Influence of Body Composition on Arterial Stiffness in Middle-Aged Adults: Healthy UAL Cross-Sectional Study

Background and objectives: Several anthropometric and body composition parameters have been linked to arterial stiffness (AS) as a biomarker of cardiovascular disease. However, little is known about which of these closely related factors is more strongly associated with AS. The aim of the present study was to analyze the relationship of different anthropometric and body composition parameters with AS in middle-aged adults. Materials and Methods: This cross-sectional study included 186 middle-aged participants (85 women, 101 men; age = 42.8 ± 12.6 years) evaluated as part of the Healthy UAL study, a population study conducted at the University of Almería with the main purpose of analyzing the etiology and risk factors associated with cardio-metabolic diseases. Anthropometric measures included neck, waist, and hip circumferences, as well as the waist-to-height ratio (WHtr). Bioimpedance-derived parameters included fat-free mass index (FFMI), fat mass index (FMI), and percent of body fat (%BF). AS was measured by pulse wave velocity (PWV). The relationships of interest were examined through stepwise regression analyses in which age and sex were also introduced as potential confounders. Results: Neck circumference (in the anthropometric model; R²: 0.889; β: age = 0.855, neck = 0.204) and FFMI (in the bio-impedance model; R²: 0.891; β: age = 0.906, FFMI = 0.199) emerged as significant cross-sectional predictors of AS. When all parameters were included together (both anthropometry and bio-impedance), both neck circumference and FFMI appeared again as being significantly associated with AS (R²: 0.894; β: age = 0.882, FFMI = 0.126, neck = 0.093). Conclusion: It was concluded that FFMI and neck circumference are correlated with AS regardless of potential confounders and other anthropometric and bioimpedance-derived parameters in middle-aged adults.

Changes in fat mass and fat-free-mass are associated with incident hypertension in four population-based studies from Germany

BACKGROUND

We estimated the association of changes in body weight, waist circumference (WC), fat mass (FM) and fat-free mass (FFM) with changes in blood pressure and incident hypertension using data from four German population-based studies.

METHODS

We analyzed data from 4467 participants, aged 21 to 82 years not taking antihypertensive medication and not having type 2 diabetes mellitus or a history of myocardial infarction at baseline and follow-up, from four population-based studies conducted in Germany. Body weight, WC, and blood pressure were measured at baseline and follow-up (median follow-up of the single studies 4 to 7 years). FM and FFM were calculated based on height-weight models derived from bioelectrical impedance studies. Hypertension was defined as systolic blood pressure ≥ 140 mmHg or diastolic blood pressure ≥ 90 mmHg. Confounder-adjusted linear and logistic regressions were used to associate changes in anthropometric markers with changes in blood pressure, incident hypertension, and incident normalization of blood pressure.

RESULTS

In a pooled dataset including all four studies, increments in body weight, WC, FM, and FFM were statistically significantly associated with incident hypertension and changes in systolic and diastolic blood pressure over time. Decreases in body weight, FM, and FFM were significantly associated with incident normalization of blood pressure.

CONCLUSIONS

Our data suggests that the well-established association between obesity and blood pressure levels might be more related to body composition rather than to total body weight per se. Our findings indicate that gaining or losing FFM has substantial impact on the development or reversion of hypertension.

Elevated blood pressure in adolescent girls: correlation to body size and composition

Background

To improve understanding of the pathophysiology of hypertension in adolescents and pave the way for risk stratification, studies have sought to determine the correlates of blood pressure (BP). Inconsistencies in dependent and independent variables have resulted in an elusive consensus. The aim of this report is to examine an inclusive array of correlates of BP, as a continuous (systolic and diastolic BP) and a dichotomous variable.

Methods

Subjects were a school-based sample of 730 urban, mostly African American, non-referred 6th and 7th grade girls. To find independent correlates of SBP/DBP, we used a stepwise model selection method based on the Schwarz Bayesian Information Criterion, enabling selection of a parsimonious model among highly correlated covariates. Candidate variables were: age, stature, heart rate, pubertal development, BMI, BMI z-score, waist circumference, waist-to-height ratio (WHtR), body surface area, fat mass (by bioelectrical impedance analysis), fat-free mass (FFM), percentage of body fat, and presence of overweight/obesity.

Results

The best-fitting models for DBP and SBP (considered separately) included fat-free mass, heart rate and, in the case of SBP, stature. The best-fitting model for high-normal/elevated blood pressure (H-N/EBP) included WHtR with no independent relation of any other variable. The prevalence of H-N/EBP tripled between a WHtR of 0.5 and 0.7.

Conclusions

The easily obtained and calculated WHtR is the strongest correlate of elevated blood pressure among available variables and is a prime candidate for longitudinal studies of predictors of the development of hypertension.

Trial registration

ClinicalTrials.gov Identifier, NCT00746083

Influence of obesity on blood pressure and arterial stiffness in the early teens

PROBLEM

We studied the influence of adiposis on the progression of blood pressure and arteriosclerosis in the early teens.

METHODS

The subjects of this study were 147 boys and girls (72 boys and 75 girls) in junior high school. Height, weight, percentage body fat, blood pressure, brachial-ankle pulse wave velocity (baPWV) and exercise time were measured. All subjects were measured at two points--at 5th grade in elementary school (ages between 10 and 11 years) and 2nd grade in junior high school (8th grade, ages between 13 and 14 years). The relationship between the change values of adiposis over 3 years (from 5th grade to 8th grade) and blood pressure/baPWV at the age of 13-14 were analyzed with multiple regression analysis.

RESULTS

For boys, the change values in BMI and percentage body fat were correlated positively with systolic blood pressure. For girls, the change values in BMI and percentage body fat were correlated positively with systolic and diastolic blood pressures and baPWV.

CONCLUSIONS

In conclusion, raised blood pressure was already observed in obese early teens as a result of arteriosclerosis progression regardless exercise habit, and it was more apparent in girls.

The relationships of body mass index, waist-to-height ratio, and body fat percentage with blood pressure and its hemodynamic determinants in Korean adolescents: a school-based study

Purpose

Obesity is an important risk factor for hypertension in adolescents. We investigated the relationship of obesity-related indices (body mass index [BMI], waist-to-height ratio [WHR], and body fat percentage [%BF]) with blood pressure and the hemodynamic determinants of blood pressure in Korean adolescents.

Methods

In 2008, 565 adolescents, aged 12-16 years, were examined. The %BF of the participants was measured by bioelectrical impedance analysis. Echocardiography and brachial artery pulse tracing were used to estimate the stroke volume (SV), cardiac output (CO), total vascular resistance (TVR), and total arterial compliance (TAC).

Results

We noted that BMI, WHR, and %BF were positively correlated with systolic blood pressure (SBP) and diastolic blood pressure (DBP). The positive correlation between BMI and blood pressure (SBP and DBP) persisted after adjustment for WHR and %BF. However, after adjustment for BMI, the positive associations between blood pressure (SBP and DBP) and WHR as well as %BF, were not noted. With regard to the hemodynamic factors, BMI, but not WHR and %BF, was an independent positive factor correlated with SV and CO. TVR had an independent negative association with BMI; however, it was not associated with WHR or %BF. Moreover, we noted that BMI, WHR, and %BF did not affect TAC.

Conclusion

In Korean adolescents, BMI had an independent positive correlation with SBP and DBP, possibly because of its effects on SV, CO, and TVR. WHR and %BF are believed to indirectly affect SBP and DBP through changes in BMI.

Clustering of the metabolic syndrome components in adolescence: role of visceral fat

Visceral fat (VF) promotes the development of metabolic syndrome (MetS), which emerges as early as in adolescence. The clustering of MetS components suggests shared etiologies, but these are largely unknown and may vary between males and females. Here, we investigated the latent structure of pre-clinical MetS in a community-based sample of 286 male and 312 female adolescents, assessing their abdominal adiposity (VF) directly with magnetic resonance imaging. Principal component analysis of the five MetS-defining variables (VF, blood pressure [BP], fasting serum triglycerides, HDL-cholesterol and glucose) identified two independent components in both males and females. The first component was sex-similar; it explained >30% of variance and was loaded by all but BP variables. The second component explained >20% of variance; it was loaded by BP similarly in both sexes but additional loading by metabolic variables was sex-specific. This sex-specificity was not detected in analyses that used waist circumference instead of VF. In adolescence, MetS-defining variables cluster into at least two sub-syndromes: (1) sex-similar metabolic abnormalities of obesity-induced insulin resistance and (2) sex-specific metabolic abnormalities associated with BP elevation. These results suggest that the etiology of MetS may involve more than one pathway and that some of the pathways may differ between males and females. Further, the sex-specific metabolic abnormalities associated with BP elevation suggest the need for sex-specific prevention and treatment strategies of MetS.

Hemodynamic effect of atrioventricular and interventricular dyssynchrony in patients with biventricular pacing: Implications for the pacemaker syndrome

Background/Objectives:

Pacemaker syndrome was mainly described as the sequel of atrioventricular (AV) dyssynchrony. The role of interventricular (VV) dyssynchrony has not been studied yet. The aims of this study were to noninvasively assess the hemodynamic effects of different ventricular pacing sites with and without AV and VV dyssynchrony and to observe the patients for clinical symptoms of the pacemaker syndrome during the AV sequential and ventricular-only pacing modes.

Materials and Methods:

Between March 2009 and February 2010, 40 patients (28 men; mean age, 61 ± 15 years) with biventricular (BiV) device were enrolled. Mean systolic and diastolic blood pressures (BP) of 5 beats were measured 5 minutes after each mode change using fingertip plethysmography. The patients were also observed for the occurrence of symptoms suggestive of the pacemaker syndrome, including dyspnea, palpitations, dizziness, presyncope, and syncope.

Results:

There was no difference in mean systolic BP among different ventricular-only pacing modes (all P = NS). However, mean systolic BP was significantly higher in AV sequential biventricular pacing (DDD-BiV) compared with ventricular-only pacing modes (all P<0.05). In addition, there was no difference in terms of pacemaker syndrome-related symptoms following mode change from DDD-BiV to DDD-RV or DDD-LV (all P>0.05).

Conclusions:

The present study showed that the non-AV sequential BiV and LV pacing may have no significant benefit compared with RV pacing in terms of systolic blood pressure. However, there was marked hemodynamic improvement following mode change to AV sequential BiV pacing. This study may have important implications for pathogenesis of pacemaker syndrome.

Relationship between obesity and pulse pressure in children: results of the National Health and Nutrition Survey (NHANES) 1988-1994

BACKGROUND

Obesity is a known cardiometabolic risk factor in children. In adults, pulse pressure (PP) is a known predictor and a risk factor of cardiovascular (CV) diseases. In this study, we examined the association between measures of obesity and PP in children.

METHODS

A retrospective analysis of 4667 children ages 6-17 years from the National Health and Nutrition Survey (1988-1994) was performed. We defined wide PP as 4th quartile PP and high waist circumference (WC) as >75th percentile based on age and gender.

RESULTS

There were 51% boys, 74% whites, 16% blacks, 10% Hispanics, 12% obese, 26% with high WC, 26% with wide PP, and 9% with high blood pressure (BP). Prevalence of wide PP was high among obese children. A significantly higher mean PP was observed in boys, Blacks, obese, those with high WC and high BP. The adjusted odds ratio (OR) for wide PP was higher in boys, Blacks, and those with high WC.

CONCLUSION

There was a statistically significant independent association observed between wide PP and high WC, but not with obesity based on BMI. Further exploration of wide PP as a CV risk factor in childhood and its relationship to CV outcomes appears warranted.

Sex differences in the contributions of visceral and total body fat to blood pressure in adolescence

Excess body fat deposited viscerally rather than elsewhere in the body is associated with higher risk for hypertension; this relationship is stronger in men than in women. Here we investigated whether similar sex dimorphism exists already in adolescence. A population-based sample of adolescent boys (n=237) and girls (n=262), age 12 to 18 years, was studied. Total body fat (TBF) was assessed with multifrequency bioelectrical impedance, and visceral fat (VF) was quantified with MRI. Blood pressure (BP) was measured beat by beat during an hour-long protocol, including supine, standing, sitting, mental stress, and poststress sections. Multivariate mixed-model analysis was used to assess the relative contributions of TBF and VF to BP during these sections. In boys, BP was strongly positively associated with VF (P<0.0001), whereas it was less strongly and negatively associated with TBF (P=0.004); these relationships did not substantially vary during the protocol. In contrast, in girls, BP was strongly positively associated with TBF (P=0.0006), whereas it was not associated with VF (P=0.08); the relationship with TBF varied during the protocol and was most apparent during mental stress (TBF*section interaction: P=0.002). Furthermore, when waist circumference was included in multivariate models instead of VF, it was not associated with BP in either sex; this indicates that waist circumference may not be an appropriate surrogate for VF. Thus, in adolescence, adiposity-related BP elevation is driven mainly by visceral fat in males and by fat deposited elsewhere in females. This dimorphism suggests sex-specific mechanisms of obesity-induced hypertension and the need for sex-specific criteria of its prevention.

Body fat and blood pressure: comparison of blood pressure measurements in Chinese children with different body fat levels

Children in China are experiencing a rapid increase in the prevalence of obesity, which is associated with hypertension. To compare the effect of body fat on blood pressure (BP) with that of the normal physical growth, we compared BP levels in Chinese children with different body fat levels. In the present population-based study, 13 972 children in the highest-skinfold-thickness-quartile group were individually matched to 13 972 children in the lowest-skinfold-thickness-quartile group by height and weight. Similarly, 5103 children in the highest-waist-circumference-quartile group were matched to the same number of children in the lowest-waist-circumference-quartile group. The high- and low-fat groups had similar height and weight but the high-fat group had significantly higher skinfold and waist circumference measurements. The differences in systolic BP (SBP) between the high- and low-skinfold-thickness groups were small: 0·01 (95 % CI − 0·41, 0·44) mmHg in boys and 0·20 (95 % CI − 0·15, 0·54) mmHg in girls. The differences in diastolic BP (DBP) were also small (0·39 and 0·38 mmHg for boys and girls, respectively) but were statistically significant. The differences in both SBP and DBP between the high- and low-waist-circumference groups were small but not statistically significant. For a given body size as measured by height and weight, relative body fat had little impact on BP levels in these children. Fat mass and lean mass may have a similar quantitative impact on BP in healthy-weight children.

The role of obesity, salt and exercise on blood pressure in children and adolescents

The increasing trends of blood pressure (BP) in children and adolescents pose great concern for the burden of hypertension-related cardiovascular disease. Although primary hypertension in childhood is commonly associated with obesity, it seems that other factors, such as dietary sodium and exercise, also influence BP levels in children and adolescents. Several studies support that sympathetic nervous system imbalance, impairment of the physiological mechanism of pressure natriuresis, hyperinsulinemia and early vascular changes are involved in the mechanisms causing elevated BP in obese children and adolescents. Under the current evidence on the association of salt intake and BP, dietary sodium restriction appears to be a rational step in the prevention of hypertension in genetically predisposed children and adolescents. Finally, interventional studies show that regular aerobic exercise can significantly reduce BP and restore vascular changes in obese with hypertensive pediatric patients. This article aims to summarize previous studies on the role of obesity, salt intake and exercise on BP in children and adolescents.

Gender differences in artery wall biomechanical properties throughout life

Elevated large artery stiffness and pulse pressure have emerged as important risk factors for cardiovascular disease. The genders differ in large artery biomechanical properties throughout the lifespan with females displaying higher stiffness than males during the prepubertal years and a dramatic increase after menopause. Males on the other hand experience an increase in arterial stiffness postpuberty and a linear increase thereafter, suggesting that females have intrinsically stiffer large arteries than males, but that such effects are mitigated by sex steroids during the reproductive years. This review discusses anthropometric and sex steroid influences on gender differences in large artery stiffness and pressure dynamics from childhood to senescence. In particular, the sex-specific effects of estrogen, progesterone and testosterone on vascular structure and function and how these influence arterial stiffness are explored. These factors may contribute in part to the observed gender differences in the pathophysiology and clinical manifestations of cardiovascular disease.

Relationships between serial childhood adiposity measures and adult blood pressure: The Fels longitudinal study

OBJECTIVES

Several studies have shown that causes of adult hypertension arise in childhood, and obesity may be a potential cause or at least a mitigating factor in this development. Body mass index is a well studied obesity metric, yet other potential adiposity measures such as percent body fat and waist circumference have been somewhat less considered. The purpose of this study is to determine associations between these alternative serial childhood adiposity measures and adulthood blood pressure.

METHODS

Measurements from participants in the Fels Longitudinal Study were used to summarize childhood adiposity, represented by childhood measurements of percent body fat and height-adjusted waist circumference. These subjects also provided systolic and diastolic blood pressure as adults. Childhood adiposity levels were categorized as high or low as compared to the respective upper quartile, and associations with adult blood pressure were measured using Poisson regression to estimate the number of expected occurrences of elevated adiposity during childhood. Adult lifestyle covariates and adiposity were accounted for using multiple linear regression.

RESULTS

Summary indices of the childhood adiposity measures were significantly associated with both adult blood pressure metrics in men and women, though some of these associations were altered or reduced in the presence of adult lifestyle characteristics and adult adiposity measures.

CONCLUSIONS

Childhood measures of percent body fat and height-adjusted waist circumference have an effect on adult blood pressure, though the effect can be mitigated by adult lifestyles.

Left ventricular structure and function in children with and without developmental coordination disorder

Children with developmental coordination disorder (DCD) are more likely to develop cardiovascular disease risk factors such as obesity and reduced cardio-respiratory fitness. However, there is limited data using laboratory measures for assessing the risk of cardiovascular disease associated with DCD. The purpose of this study was to examine differences in left ventricular structure and function between children with DCD and healthy controls. The study involved 126 children (aged 12-13 years) with significant motor impairment (n = 63) and healthy controls (n = 63) matched for age, sex, and school. The Movement ABC test (M-ABC2) was used to classify children as probable DCD (p-DCD). Cardiac dimensions were measured using ultrasound echocardiography. Left ventricular mass (LVM) was elevated in children with p-DCD (89 ± 17 g) compared to controls (87 ± 21 g), however, this difference was not significant. When LVM was normalized to height(2.7), no difference was evident between groups (26 g and 26 g for the p-DCD and controls, respectively). However, the p-DCD group demonstrated significantly elevated stroke volume (p = 0.02), cardiac output (p<0.001), end-diastolic volume (p = 0.03), and left ventricle diameter in diastole (p = 0.02). Also, peak VO(2) normalized for fat free mass (FFM) was significantly lower (p = 0.001) and systolic blood pressure (p = 0.01), body mass index (p = 0.001), heart rate (p = 0.005) and percent body fat (p<0.001) were significantly higher in p-DCD. In regression analyses, p-DCD was a significant predictor of stroke volume and cardiac output even after accounting for height, FFM, VO(2FFM), and sex. Children with p-DCD do not demonstrate significantly elevated LVM or depressed systolic function compared to healthy controls. However, cases with p-DCD demonstrate significantly elevated end-diastolic volume, diastolic chamber size, stroke volume, and cardiac output. These differences indicate obesity related changes in the left ventricle and may represent the early stages of developing left ventricle hypertrophy.

Low vs. higher-dose dark chocolate and blood pressure in cardiovascular high-risk patients

BACKGROUND

Dark chocolate may have blood pressure-lowering properties. We conducted a prospective randomized open-label blinded end-point design trial to study a potential dose dependency of the presumed antihypertensive effect of dark chocolate by directly comparing low vs. higher doses of dark chocolate over the course of 3 months.

METHODS

We enrolled a total of 102 patients with prehypertension/stage 1 hypertension and established cardiovascular end-organ damage or diabetes mellitus. Patients were randomly assigned to receive either 6 or 25 g/day of flavanol-rich dark chocolate for 3 months. The difference in 24-h mean blood pressure between groups was defined as the primary outcome measure.

RESULTS

Significant reductions in mean ambulatory 24-h blood pressure were observed between baseline and follow-up in both groups (6 g/day: -2.3 mm Hg, 95% confidence interval -4.1 to -0.4; 25 g/day: -1.9 mm Hg, 95% confidence interval -3.6 to -0.2). There were no significant differences in blood pressure changes between groups. In the higher-dose group, a slight increase in body weight was noted (0.8 kg, 95% confidence interval 0.06 to 1.6).

CONCLUSIONS

The findings are consistent with the hypothesis that dark chocolate may be associated with a reduction in blood pressure (BP). However, due to the lack of a control group, confounding may be possible and the results should be interpreted with caution.

Hypertension after pediatric cardiac transplantation: detection, etiology, implications and management

While it may rescue children with end-stage heart failure from impending catastrophe, cardiac transplantation leaves 50-70% of pediatric recipients with new-onset hypertension. Given the unique vulnerability of the heart and kidneys in these children, we can expect long-term uncontrolled hypertension to shorten both graft and patient survival. In this review we discuss the multi-factorial etiology of post-transplant hypertension, highlighting current uncertainties and emphasizing mechanisms specific to cardiac recipients. We consider the optimal means of monitoring BP and in particular, the advantages of 24 h-ABP over intermittent clinic measurements. We also review BP treatment after cardiac transplantation, drawing attention to specific cautions appropriate when prescribing antihypertensive agents in these circumstances.

Differences in left ventricular mass between overweight and normal-weight preadolescent children

This study examined cardiac and arterial differences between overweight and normal-weight preadolescent children. Twenty children (10.2 +/- 0.4 years of age) classified as overweight, on the basis of age-appropriate body mass index (BMI) cutoffs, were compared with 43 normal-weight controls. Height, mass, and body surface area were measured. Relative body fat and lean body mass were estimated from skinfold thickness. Each child's weekly physical activity metabolic equivalent (PAME) was calculated using a standardized questionnaire, and his or her sexual maturation was self-assessed using the Tanner scale. Peak aerobic power was assessed using a cycle ergometer and normalized to lean body mass. Mean arterial pressure was calculated from systolic and diastolic blood pressure (DBP) measurements taken with a Finapres. Cardiac dimensions were measured, using Mu-mode 2-dimensional echocardiography, and normalized to body surface area and height2.7. Left carotid artery pulse pressure (CaPP) was assessed with applanation tomometry. Overweight boys and girls had a higher left ventricular mass (LVM) and LVMHT2.7 than normal-weight boys and girls. CaPP was signficantly lower in the overweight than in the normal-weight groups, whereas PAME and relative peak aerobic power were significantly higher in the boys than the girls. Although overweight children had significantly higher stroke volumes and cardiac outputs than normal-weight children, ejection fraction was similar in the weight groups. Adjusted LVMHT2.7 was associated with cardiac volume measurements, BMI, and DBP in normal-weight children, whereas in the overweight children LVMHT2.7 did not significantly correlate with any variable. In conclusion, we found that cardiovascular adaptations can be seen in prepubescent overweight children as young as 10 years of age.

Associations among obesity, blood pressure, and left ventricular mass

OBJECTIVES

To measure resting and ambulatory systemic blood pressure (BP) and left ventricular mass (LVM) in prepubertal obese and lean children and to determine their relationships.

STUDY DESIGN

Cross-sectional study including 44 obese and 22 lean prepubertal children (mean age 8.8 +/- 1.5 years). We measured casual and 24-hour ambulatory BP, LVM and LVM index (LVMI) by echocardiography, and whole body lean tissue and fat mass by dual-energy X-ray absorptiometry.

RESULTS

Mean 24-hour systolic BP (124.8 +/- 14.2 vs 105.5 +/- 8.8 mm Hg), diastolic BP (72.8 +/- 7.3 vs 62.7 +/- 3.8 mm Hg), and LVMI (36.1 +/- 5.8 vs 30.9 +/- 5.7, g x m(-2.7)) were significantly higher in obese than in lean subjects. Systolic ambulatory hypertension was present in 47.6% of obese children, and casual BP was normal in 55% of those cases. Body fatness, lean tissue mass, and 24-hour BP correlated positively with LVMI. When adjusted for body fatness, LVMI was only associated with 24-hour systolic BP (adjusted R(2) = 15.9%; P = .001).

CONCLUSIONS

Ambulatory systemic hypertension and increased LVM are found in obese children. Left ventricular mass is partially determined by systemic BP. We conclude that prevention and treatment of childhood obesity should be initiated as early as possible to prevent the premature development of hypertension and end-stage organ damage.

Association between body composition and blood pressure in a contemporary cohort of 9-year-old children

Elevated blood pressure (BP) in children is an early risk factor for cardiovascular disease and is positively associated with body mass index (BMI). However, BMI does not distinguish between fat and lean masses, and the relationship of BP in children to different elements of body composition is not well established. BP, BMI and body composition were measured in 6863 children enrolled in the Avon Longitudinal Study of Parents and Children. Fat mass, lean mass and trunk fat were assessed using dual-energy X-ray absorptiometry. After full adjustment for confounders, total body fat and BMI were positively associated with systolic blood pressure (SBP) (beta=3.29, 95% confidence interval CI 3.02, 3.57 mm Hg/standard deviation (s.d.) and beta=3.97, 95% CI 3.73, 4.21 mm Hg/s.d., respectively) and diastolic blood pressure (DBP) (beta=1.26, 95% CI 1.05, 1.46 mm Hg/s.d. and beta=1.37, 95% CI 1.19, 1.54 mm Hg/s.d., respectively). SBP was also positively associated with lean mass (beta=3.38, 95% CI 2.95, 3.81 mm Hg/s.d.), and weakly associated with trunk fat (beta=1.42, 95% CI -0.06, 2.90 mm Hg/s.d., independent of total fat mass), which was robust in girls only. The association between lean mass and SBP remained even after accounting for fat mass. SBP in 9-year-old children is independently associated with fat mass and lean mass and, to a lesser extent, trunk fat in girls. In this analysis, because both fat and lean masses are associated with BP, BMI predicts BP at least as well as these components of body composition.

Non-invasive Monitoring of Hemodynamic Changes During Hemodialysis by the Use of a Newly Developed Admittance Cardiograph

Only a little information is available for the evaluation of the complex hemodynamic changes that occur during hemodialysis. Recently, we developed the transthoracic electrical admittance cardiograph for repeated measurements of cardiac output, and monitored hemodynamic changes during hemodialysis by the use of this device. We measured cardiovascular hemodynamic and autonomic parameters non-invasively during 210 min of hemodialysis in 19 chronic hemodialysis patients who for more than 2 months had no history of cardiovascular collapses during hemodialysis. Blood pressure was monitored every 10 min using a cuff-oscillometric device (TM-2425; A & D, Tokyo, Japan). Cardiac output was monitored on a beat-by-beat basis by a newly developed electrical admittance cardiograph (NICOVIEW PA1100; NEC, Tokyo, Japan). Electrocardiogram R-R intervals were also monitored by the TM-2425. Power spectral analysis of R-R intervals was performed to obtain the low-frequency (LF; 0.05-0.15 Hz) and the high-frequency (HF; 0.15-0.40 Hz) components based on an autoregressive model. Change in circulatory blood volume was also monitored by a CRIT-LINE (In-Line Diagnostics, Riverdale, UT, USA). Although blood volume declined significantly by 16.3 +/- 1.4% (mean +/- SE) during hemodialysis (P < 0.0001), mean blood pressure did not change significantly. Heart rate increased significantly from the initial values of 76.3 +/- 3.4-86.4 +/- 4.9 beats/min (P = 0.03). Cardiac output and stroke volume decreased significantly from 4.47 +/- 0.30 to 2.91 +/- 0.32 L/min (P < 0.0001), and from 57.0 +/- 3.7 to 33.9 +/- 3.1 mL (P < 0.0001), respectively. Total peripheral vascular resistance increased significantly from 1940 +/- 146 to 3117 +/- 280 dyne x s x cm(5) (P < 0.0001). The LF component did not show significant change, while the HF component decreased significantly (P = 0.007), and the LF/HF ratio increased significantly (P = 0.03). These results suggest that a reduction in parasympathetic nerve activity and sympathetic nerve activation and a marked increase in total peripheral vascular resistance are responsible for the maintenance of blood pressure during hemodialysis in chronic hemodialysis patients. The admittance cardiograph seems to be one of the best options for serial measurements of cardiac output.

Hypertension: a review for clinicians

Despite the existence of a variety of consistent hypertension guidelines,the issue of inadequate management of the condition persists. The challenge for health care professionals is not only to understand and adopt the guidelines but also to take a holistic approach to patient care. In addition, clinicians need to encourage adherence to medication protocols, which will hopefully lead to an overall reduction in morbidity and mortality associated with hypertension. It is the clinician's professional responsibility to be cognizant of the emerging research on vasoactive substances as new drugs are being developed that will effect endothelial receptors. It is important that clinicians are trained appropriately in blood pressure measurement and risk factor identification and intervention.

Hostility differentially predicts cardiovascular risk factors in African American and White young adults

OBJECTIVE

Hostility may influence racial disparities in cardiovascular disease through differential associations with cardiovascular risk factors. This study explored racial variations in relations between hostility and selected cardiovascular risk factors.

METHODS

Cook-Medley Hostility (Ho) scores and 11 risk factors were examined among 66 healthy, White and African American young adults.

RESULTS

Controlling for age, gender, and body mass index, the interaction of hostility and race yielded significant (or marginal) associations with resting systolic and diastolic blood pressure (SBP, DBP), cardiac index (CI; i.e. cardiac output adjusted for body size), total peripheral resistance (TPR), insulin (INS), triglycerides (TG) and percent body fat (PBF). Contributing substantial variance, hostility was positively associated with SBP, DBP, TPR, TG and INS, and negatively associated with CI among African Americans. Conversely, hostility was negatively associated with TPR and PBF among Whites.

CONCLUSION

Hostility may confer greater cardiovascular risk among young African Americans than Whites.

Gender differences in the timing of arterial wave reflection beyond differences in body height

OBJECTIVES

The timing of arterial wave reflection affects the shape of the arterial waveform and thus is a major determinant of pulse pressure. This study assessed differences in wave reflection between genders beyond the effect of body height.

METHODS

From 1123 elderly (aged 71 +/- 5 years) currently untreated hypertensives, we selected 104 pairs of men and women with identical body height (average 164 +/- 4 cm). All subjects underwent echocardiography, including measurement of aortic arch expansion, automated blood pressure measurements, measurement of ascending aortic blood flow and simultaneous carotid artery tonometry.

RESULTS

Women had higher pulse (80 +/- 17 versus 74 +/- 17 mmHg, P < 0.05) and lower diastolic pressure (79 +/- 11 versus 82 +/- 10 mmHg, P < 0.05). Whilst heart rate was similar, women had a longer time to the systolic peak (210 +/- 28 versus 199 +/- 34 ms, P < 0.01) and a longer ejection time (304 +/- 21 versus 299 +/- 25 ms, P < 0.001). Wave reflection occurred earlier in women (time between maxima 116 +/- 55 versus 132 +/- 47 ms, P < 0.05) and augmentation index was higher (36 +/- 11 versus 28 +/- 12%, P < 0.001). Aortic diameter was smaller in women and the aortic arch was stiffer (median Ep 386 versus 302 kN/m2, P < 0.05). Hence, systemic arterial compliance was less in women (0.8 +/- 0.2 versus 1.0 +/- 0.3 ml/mmHg).

CONCLUSIONS

We conclude that elderly hypertensive men and women have a different timing of both left ventricular ejection and arterial wave reflection when both genders are matched for body height. Women have smaller and stiffer blood vessels resulting in an earlier return of the reflected wave, which is likely due to an increased pulse wave velocity in women.

Obesity and cardiovascular hemodynamic function

Marked abnormalities in cardiovascular structure and hemodynamic function are present both in normotensive and hypertensive obese individuals. Cardiac abnormalities include excentric left ventricular hypertrophy and left atrial dilatation, a finding compatible with the presence of cardiac volume overload. In contrast, hypertension, often associated with abdominal obesity, is characterized by increased peripheral resistance and concentric hypertrophy. Weight reduction can result in marked improvement of ventricular dimensions and cardiac function in patients undergoing massive weight reduction following bariatric surgery. In this paper we review recent findings that have broadened our understanding of cardiovascular hemodynamic function in obesity.