Limitations of expressing left ventricular mass relative to height and to body surface area in children

Relationship of Left Ventricular Mass to Lean Body Mass in the Obese Pediatric Population

Our primary aim was to investigate the relationship between LVM and anthropometric measures including lean body mass (LBM) in obese pediatric subjects compared to normal weight controls. A retrospective chart review identified subjects 2-18 years old who were normotensive and had normal echocardiograms between 1995 and 2020 at Boston Children's Hospital. LVM was calculated with the 5/6 area length rule from 2D echocardiograms. LBM was calculated with equations derived from dual-energy X-ray absorptiometry. Of the 2217 subjects who met inclusion criteria, 203 were obese and 2014 had normal weight. The median age was 11.9 (2.0-18.9); 46% were female. The median LVM was 94.5 g (59.3-134.3) in obese subjects vs. 78.0 g (51.5-107.7) in controls. The median LBM was 37.2 kg (18.9-50.6) in obese subjects vs. 30.5 kg (17.6-40.8) in controls. In control and obese subjects, LBM had the strongest correlation to LVM (R2 0.86, P < 0.001) and (R2 0.87, P < 0.001), respectively. There was at most a modest correlation between tissue Doppler velocity z-scores and LV mass, and the largest was Septal E' z-score in obese subjects (r = - 0.31, P = 0.006). In this cohort, LBM was found to have the strongest relationship to LVM in obese subjects. The largest correlation between tissue Doppler velocity z-scores and LV mass was Septal E' z-score. Future studies will evaluate which measurements are more closely aligned with clinical outcomes in obese children.

Is Height2.7 Appropriate for Indexation of Left Ventricular Mass in Healthy Adolescents? The Importance of Sex Differences

BACKGROUND

Left ventricular mass (LVM) is an important predictor of cardiovascular risk. In adolescence, LVM is commonly indexed to height2.7, although some evidence suggests that this may not fully account for sex differences.

METHODS

We investigated appropriate allometric scaling of LVM to height, total lean mass, and body surface area, in a UK birth cohort of 2039 healthy adolescents (17±1 years). Allometric relationships were determined by linear regression stratified by sex, following log transformation of x and y variables [log(y)=a+b×log(x)], b is the allometric exponent.

RESULTS

Log (LVM) showed linear relationships with log(height) and log(lean mass). Biased estimates of slope resulted when the sexes were pooled. The exponents were lower than the conventional estimate of 2.7 for males (mean [95% CI]=1.66 [1.30-2.03]) and females (1.58 [1.27-1.90]). When LVM was indexed to lean mass, the exponent was 1.16 (1.05-1.26) for males and 1.07 (0.97-1.16) for females. When LVM was indexed to estimated body surface area, the exponent was 1.53 (1.40-1.66) for males and 1.34 (1.24-1.45) for females.

CONCLUSIONS

Allometric exponents derived from pooled data, including men and women without adjustment for sex were biased, possibly due to sex differences in body composition. We suggest that when assessing LVM, clinicians should consider body size, body composition, sex, and age. Our observations may also have implications for the identification of young individuals with cardiac hypertrophy.

Alterations in diastolic function and cardiac geometry in children: a longitudinal study across the spectrum of dialysis and transplant

BACKGROUND

Children with kidney failure have increased risk for cardiovascular morbidities before and after transplantation. Ejection fraction is often preserved, masking cardiac dysfunction until severe. Data on longitudinal changes in diastolic function and cardiac geometry are limited.

METHODS

A prospective study was conducted to investigate longitudinal changes in diastolic function and structure pre- and post-kidney transplant compared with healthy peers. Transplant recipients (n = 41) had echocardiograms pre-transplant, 1, 18, 30, and 42 months post-transplant. The controls (n = 26) underwent one echocardiogram. Diastolic function and cardiac geometry were assessed by E/e' lateral, E/A, interventricular septal end diastole diameter, left ventricular internal end diastole diameter, left ventricular posterior wall end diastole diameter, and left atrial dimension.

RESULTS

E/e' of patients remained worse than controls until 30 months post-transplant, and E/A was impaired at all time points compared to the controls. Left ventricular geometry was abnormal in 46% pre-transplant and remained altered in 44.7%, 32.3%, 30.7%, and 27.2% at 1, 18, 30, and 42 months post-transplant. Determinants of diastolic dysfunction included hemodialysis, uncontrolled hypertension, steroid exposure, and metabolic syndrome; abnormal geometry was associated with glomerular diagnosis, dialysis duration, obesity, steroids, and metabolic syndrome. Abnormal diastolic function and structure were associated with left ventricular hypertrophy.

CONCLUSION

Diastolic dysfunction and geometry partially improve after transplant but remain abnormal in a subset of patients compared to healthy peers. Traditional indicators of systolic function are preserved. Modifiable risk factors include dialysis modality and duration, uncontrolled hypertension, corticosteroids, obesity, and metabolic syndrome. Attention to diastolic changes provides opportunity for early intervention. A higher resolution version of the Graphical abstract is available as Supplementary information.

Effects of blood pressure percentile, body mass index, and race on left ventricular mass in children

OBJECTIVE

To evaluate the association of systolic blood pressure percentile, race, and body mass index with left ventricular hypertrophy on electrocardiogram and echocardiogram to define populations at risk.

STUDY DESIGN

This is a retrospective cross-sectional study design utilising a data analytics tool (Tableau) combining electrocardiogram and echocardiogram databases from 2003 to 2020. Customized queries identified patients aged 2-18 years who had an outpatient electrocardiogram and echocardiogram on the same date with available systolic blood pressure and body measurements. Cases with CHD, cardiomyopathy, or arrhythmia diagnoses were excluded. Echocardiograms with left ventricle mass (indexed to height^2.7) were included. The main outcome was left ventricular hypertrophy on echocardiogram defined as Left ventricle mass index greater than the 95th percentile for age.

RESULTS

In a cohort of 13,539 patients, 6.7% of studies had left ventricular hypertrophy on echocardiogram. Systolic blood pressure percentile >90% has a sensitivity of 35% and specificity of 82% for left ventricular hypertrophy on echocardiogram. Left ventricular hypertrophy on electrocardiogram was a poor predictor of left ventricular hypertrophy on echocardiogram (9% sensitivity and 92% specificity). African American race (OR 1.31, 95% CI = 1.10, 1.56, p = 0.002), systolic blood pressure percentile >95% (OR = 1.60, 95% CI = 1.34, 1.93, p < 0.001), and higher body mass index (OR = 7.22, 95% CI = 6.23, 8.36, p < 0.001) were independently associated with left ventricular hypertrophy on echocardiogram.

CONCLUSIONS

African American race, obesity, and hypertension on outpatient blood pressure measurements are independent risk factors for left ventricular hypertrophy in children. Electrocardiogram has little utility in the screening for left ventricular hypertrophy.

Pericardial adipose tissue, cardiac structures, and cardiovascular risk factors in school-age children

Aims 

We examined the associations of pericardial adipose tissue with cardiac structures and cardiovascular risk factors in children.

Methods and results 

We performed a cross-sectional analysis in a population-based cohort study among 2892 children aged 10 years (2404 normal weight and 488 overweight/obese). Pericardial adipose tissue mass was estimated by magnetic resonance imaging (MRI) and indexed on height³. Left ventricular mass (LVM) and left ventricular mass-to-volume ratio (LMVR) were estimated by cardiac MRI. Cardiovascular risk factors included android adipose tissue percentage obtained by Dual-energy X-ray absorptiometry, blood pressure and glucose, insulin, cholesterol, and triglycerides concentrations. Adverse outcomes were defined as values above the 75 percentile. Median pericardial adipose tissue index was 3.6 (95% range 1.6–7.1) among normal weight and 4.7 (95% range 2.0–8.9) among overweight children. A one standard deviation (1 SD) higher pericardial adipose tissue index was associated with higher LMVR [0.06 standard deviation scores, 95% confidence interval (CI) 0.02–0.09], increased odds of high android adipose tissue [odd ratio (OR) 2.08, 95% CI 1.89–2.29], high insulin concentrations (OR 1.17, 95% CI 1.06–1.30), an atherogenic lipid profile (OR 1.22, 95% CI 1.11–1.33), and clustering of cardiovascular risk factors (OR 1.56, 95% CI 1.36–1.79). Pericardial adipose tissue index was not associated with LVM, blood pressure, and glucose concentrations. The associations showed largely the same directions but tended to be weaker among normal weight than among overweight children.

Conclusion 

Pericardial adipose tissue is associated with cardiac adaptations and cardiovascular risk factors already in childhood in both normal weight and overweight children.

Height Versus Body Surface Area to Normalize Cardiovascular Measurements in Children Using the Pediatric Heart Network Echocardiographic Z-Score Database

Normalizing cardiovascular measurements for body size allows for comparison among children of different ages and for distinguishing pathologic changes from normal physiologic growth. Because of growing interest to use height for normalization, the aim of this study was to develop height-based normalization models and compare them to body surface area (BSA)-based normalization for aortic and left ventricular (LV) measurements. The study population consisted of healthy, non-obese children between 2 and 18 years of age enrolled in the Pediatric Heart Network Echo Z-Score Project. The echocardiographic study parameters included proximal aortic diameters at 3 locations, LV end-diastolic volume, and LV mass. Using the statistical methodology described in the original project, Z-scores based on height and BSA were determined for the study parameters and tested for any clinically significant relationships with age, sex, race, ethnicity, and body mass index (BMI). Normalization models based on height versus BSA were compared among underweight, normal weight, and overweight (but not obese) children in the study population. Z-scores based on height and BSA were calculated for the 5 study parameters and revealed no clinically significant relationships with age, sex, race, and ethnicity. Normalization based on height resulted in lower Z-scores in the underweight group compared to the overweight group, whereas normalization based on BSA resulted in higher Z-scores in the underweight group compared to the overweight group. In other words, increasing BMI had an opposite effect on height-based Z-scores compared to BSA-based Z-scores. Allometric normalization based on height and BSA for aortic and LV sizes is feasible. However, height-based normalization results in higher cardiovascular Z-scores in heavier children, and BSA-based normalization results in higher cardiovascular Z-scores in lighter children. Further studies are needed to assess the performance of these approaches in obese children with or without cardiac disease.

Alternative to body surface area as a solution to correct systematic bias in pediatric echocardiography Z scores

BACKGROUND

Z scores are the method of choice to report dimensions in pediatric echocardiography. Z scores based on body surface area (BSA) have been shown to cause systematic biases in overweight and obese children. Using aortic valve (AoV) diameters as a paradigm, the aims of this study were to assess the magnitude of Z score underestimation in children with increased body mass index Z score (BMI-Z) and to determine if a predicting model with height and weight as independent predictors would minimize this bias.

METHODS

In this multicenter, retrospective, cross-sectional study, 15,006 normal echocardiograms in healthy children 1-18 years old were analyzed. Residual associations with body size were assessed for previously published Z score. BSA-based and alternative prediction models based on height and weight were developed and validated in separate training and validation samples.

RESULTS

Existing BSA-based Z scores incompletely adjusted for weight, BSA and BMI-Z and led to an underestimation of >0.8 Z score units in subjects with higher BMI-Z, compared to lean subjects. BSA-based models led to overestimation of predicted AoV diameters with increasing weight or BMI-Z. Models using height and weight as independent predictors improved adjustment with body size, including in children with higher BMI-Z.

CONCLUSIONS

BSA-based models result in underestimation of Z scores in patients with high BMI-Z. Prediction models using height and weight as independent predictors minimize residual associations with body size and generate well-fitted predicted values that could apply to all children, including those with low or high BMI-Z.

Dilatation of the Ascending Aorta in Turner Syndrome: Influence of Bicuspid Aortic Valve Morphology and Body Composition

BACKGROUND

Aortic dilatation and bicuspid aortic valve (BAV) are frequent in Turner syndrome (TS). Due to short stature, aortic size index (ASI)-ascending aortic diameter (AD)/body surface area (BSA)-is used to identify aortic dilatation in TS patients. We sought to: 1) describe echocardiographic findings in the largest cohort of Australian women with TS; 2) assess if ASI progresses differently with age in TS BAV compared to non-syndromic BAV; and 3) determine whether adjustment of AD for body composition may be superior to BSA indexation.

METHODS

Transthoracic echocardiography (TTE) data were retrospectively collected on 125 women with TS. Body composition was quantified by dual energy X-ray absorptiometry (DXA) in 60 women within 6 months of baseline TTE. Age-matched females with non-syndromic BAV (n=170) were used as controls for TS patients with BAV.

RESULTS

Mean age of TS women was 28±16 years, and mean height and BSA were 141.6±21.7 cm and 1.4±0.4 m², respectively. Mean AD was 2.5±0.8 cm, and ASI 2.0±0.6 cm/m². Aortic dilatation (ASI >2.0 cm/m²) was present in 42 (34%) patients. Turner syndrome women with BAV (n=34; 27%) had a larger ASI than those with tri-leaflet AV (2.2±0.4 cm/m² vs. 1.7±0.3 cm/m², p<0.001). In the pooled BAV cohort, TS patients had a higher baseline ASI (2.2±0.4 cm/m² vs. 2.1±0.3 cm/m², p=0.02) and greater increase in ASI with age (0.21 mm/m²/year vs. 0.10 mm/m²/year, p=0.01) compared to non-syndromic BAV patients. DXA fat-free mass (r=0.33, p=0.01) and lean mass (r=0.32, p=0.02) correlated with AD, as did BSA (r=0.62, p<0.001).

CONCLUSION

Turner syndrome women with BAV have a greater degree of baseline aortic dilatation and a twofold faster increase in aortic dimension with age when compared to matched women with non-syndromic BAV. Several DXA-derived body composition parameters correlate with aortic size in TS, however BSA appears to be the most robust method of indexation.

Left ventricular mass normalization in child and adolescent athletes must account for sex differences

Background

To assess left ventricular hypertrophy, actual left ventricular mass (LVM) normalized for body size has to be compared to the LVM normative data. However, only some published normative echocardiographic data have been produced separately for girls and boys; numerous normative data for the pediatric population are not sex-specific. Thus, this study aimed to assess whether the LVM normative data should be developed separately for girls and boys practicing sports.

Methods

Left ventricular mass was computed for 331 girls and 490 boys, 5–19 years old, based on echocardiography. The effect of sex on the relationship between LVM and body size was evaluated using a linear regression model. Seven sets of the LVM normative data were developed, using different methodologies, to test concordance between sex-specific and non-specific normative data. Every set consisted of normative data that was sex-specific and non-specific. Upon these normative data, for every study participant, seven pairs of LVM z-scores were calculated based on her/his actual LVM. Each pair consisted of z-scores computed based on sex-specific and non-specific normative data from the same set.

Results

The regression lines fitted to the data points corresponding to LVM of boys had a higher slope than of girls, indicating that sex affects the relationship between LVM and body size. The mean differences between the paired LVM z-scores differed significantly from 0. The percentage of discordant indications, depending on the normalization method, ranged from 66.7% to 100% in girls and from 35.4% to 50% in boys. Application of the LVM normative data that were not sex-specific made relative LVM underestimated in girls and overestimated in boys.

Conclusion

The LVM normative data should be developed separately for girls and boys practicing sports. Application of normative data that are not sex-specific results in an underestimation of relative LVM in girls and overestimation in boys.

Novel Z Scores to Correct Biases Due to Ventricular Volume Indexing to Body Surface Area in Adolescents and Young Adults

BACKGROUND

Reference values for cardiac magnetic resonance imaging (cMRI) in children and young adults are scarce. This leads to risk stratification of patients with congenital heart diseases being based on volumes indexed to body surface area (BSA). We aimed to produce cMRI Z score equations for ventricular volumes in children and young adults and to test whether indexing to BSA resulted in an incorrect assessment of ventricular dilation according to sex, body composition, and growth.

METHODS

We retrospectively included 372 subjects aged < 26 years with either normal hearts or conditions with no impact on ventricular volumes (reference group), and 205 subjects with repaired tetralogy of Fallot (TOF) aged < 26 years. We generated Z score equations by means of multivariable regression modelling. Right ventricular dilation was assessed with the use of Z scores and compared with indexing to BSA in TOF subjects.

RESULTS

Ventricular volume Z scores were independent from age, sex, and anthropometric measurements, although volumes indexed to BSA showed significant residual association with sex and body size. In TOF subjects, indexing overestimated dilation in growing children and underestimated dilation in female compared with male subjects, and in overweight compared with lean subjects.

CONCLUSIONS

Indexed ventricular volumes measured with cMRI did not completely adjust for body size and resulted in a differential error in the assessment of ventricular dilation according to sex and body size. Our proposed Z score equations solved this problem. Future studies should evaluate if ventricular volumes expressed as Z scores have a better prognostic value than volumes indexed to BSA.

Lean body mass is the strongest anthropometric predictor of left ventricular mass in the obese paediatric population

BACKGROUND

Indexing left ventricular mass to body surface area or height2.7 leads to inaccuracies in diagnosing left ventricular hypertrophy in obese children. Lean body mass predictive equations provide the opportunity to determine the utility of lean body mass in indexing left ventricular mass. Our objectives were to compare the diagnostic accuracy of predicted lean body mass, body surface area, and height in detecting abnormal left ventricle mass in obese children.

METHODS

Obese non-hypertensive patients aged 4-21 years were recruited prospectively. Dual-energy X-ray absorptiometry was used to measure lean body mass. Height, weight, sex, race, and body mass index z-score were used to calculate predicted lean body mass.

RESULTS

We enrolled 328 patients. Average age was 12.6 ± 3.8 years. Measured lean body mass had the strongest relationship with left ventricular mass (R2 = 0.84, p < 0.01) compared to predicted lean body mass (R2 = 0.82, p < 0.01), body surface area (R2 = 0.80, p < 0.01), and height2.7 (R2 = 0.65, p < 0.01). Of the clinically derived variables, predicted lean body mass was the only measure to have an independent association with left ventricular mass (β = 0.90, p < 0.01). Predicted lean body mass was the most accurate scaling variable in detecting left ventricular hypertrophy (positive predictive value = 88%, negative predictive value = 99%).

CONCLUSIONS

Lean body mass is the strongest predictor of left ventricular mass in obese children. Predicted lean body mass is the most accurate anthropometric scaling variable for left ventricular mass in left ventricular hypertrophy detection. Predicted lean body mass should be considered for clinical use as the body size correcting variable for left ventricular mass in obese children.

Echocardiographic Findings in a Cohort of Perinatally HIV-Infected Adolescents Compared with Uninfected Peers from the Cape Town Adolescent Antiretroviral Cohort

BACKGROUND

Little is known about the cardiac health of perinatally HIV-infected (PHIV+) adolescents on antiretroviral therapy (ART) in sub-Saharan Africa. The authors examined cardiac structure and function in PHIV+ adolescents on ART compared with HIV-uninfected (HIV-) adolescents.

METHODS

Echocardiography was performed on PHIV+ and age- and sex-frequency-matched HIV- adolescents enrolled in the Cape Town Adolescent Antiretroviral Cohort. Participants were eligible if they were 9 to 14 years of age and had been on ART for ≥6 months.

RESULTS

Overall, 474 PHIV+ adolescents (median age, 12 years; 51% boys; mean age at ART initiation, 5 years) and 109 HIV- adolescents (median age, 11.8 years; 45% boys) were included. The mean duration on ART was 7 years, with 37% starting treatment before 2 years of age. Compared with HIV- adolescents, PHIV+ adolescents had higher median Z scores for left ventricular (LV) internal end-diastolic dimension, LV end-systolic posterior wall thickness, and end-systolic interventricular septal thickness. PHIV+ adolescents had a lower median Z score for right ventricular internal end-diastolic dimension as compared with HIV- adolescents. There was no difference in ejection fraction or diastolic function between groups. Later initiation of ART (after 6 years) was associated with increased risk for LV hypertrophy (odds ratio, 2.9; 95% CI, 1.3-6.6; P = .01) compared with those who started ART earlier. PHIV+ adolescents with World Health Organization stage IV HIV infection were at increased risk (odds ratio, 2.2; 95% CI, 1.0-4.6; P = .05) of having LV diastolic dysfunction compared with those with less advanced clinical disease.

CONCLUSIONS

This study revealed subtle differences in echocardiographic parameters between PHIV+ and HIV- adolescents. Although these were not clinically significant, starting ART at an older age was a significant risk factor for LV hypertrophy, while more advanced clinical disease was associated with LV diastolic dysfunction.

Transgenerational effects of maternal obesity and gestational diabetes on offspring body composition and left ventricle mass: the Finnish Gestational Diabetes Prevention Study (RADIEL) 6-year follow-up

AIM

To investigate the influence of maternal adiposity and gestational diabetes on offspring body composition and left ventricle mass in early childhood.

METHODS

The observational follow-up study included 201 mother-child pairs, a sub-cohort from the Finnish Gestational Diabetes Prevention Study, who were recruited 6.1 ± 0.5 (mean ± SD) years postpartum, aiming for an equal number of mothers with and without gestational diabetes.

RESULTS

Maternal pre-pregnancy BMI (mean ± SD; 30.5 ± 5.6 kg/m² ) was associated with child body fat percentage [0.26 (95% CI; 0.08, 0.44)% increase in child body fat per 1 kg/m² increase in pre-pregnancy BMI of mothers with obesity] and was reflected in child BMI Z-score (mean ± SD; 0.45 ± 0.93). Left ventricle mass, left ventricle mass index and left ventricle mass Z-score were not associated with gestational diabetes, pre-pregnancy BMI or child body fat percentage. After adjusting for child sex, body fat percentage, systolic blood pressure, pre-pregnancy BMI and maternal lean body mass, left ventricle mass increased by 3.08 (95% CI; 2.25, 3.91) g for each 1 kg in child lean body mass.

CONCLUSIONS

Left ventricle mass at 6 years of age is determined predominantly by lean body mass. Maternal pre-gestational adiposity is reflected in child, but no direct association between left ventricle mass and child adiposity or evidence of left ventricle mass foetal programming related to gestational diabetes and maternal adiposity was observed in early childhood.

Left ventricular mass normalization for body size in children based on an allometrically adjusted ratio is as accurate as normalization based on the centile curves method

BACKGROUND

Normalization for body size is required for reliable left ventricular mass (LVM) evaluation, especially in children due to the large variability of body size. In clinical practice, the allometrically adjusted ratio of LVM to height raised to the power of 2.7 is often used. However, studies presenting normative LVM data for children recommend centile curves as optimal for the development of normative data. This study aimed to assess whether the allometrically adjusted LVM-to-height ratio can reliably reproduce the results of LVM normalization for height based on the centile curves method.

METHODS

Left ventricular mass was computed for 464 boys and 327 girls, 5-18 years old, based on echocardiographic examination. Normalized data representing LVM for height were developed using the centile curves construction method and two variants of the allometrically adjusted ratio method: one variant with the allometric exponents specific to the study groups, and one variant with the universal exponent of 2.7. The agreement between the allometric methods and the centile curves method was analyzed using the concordance correlation coefficient, sensitivity, and specificity.

RESULTS

For both the specific allometric variant and the universal variant, the analysis of concordance has indicated high reproducibility compared to the centile curves method. The respective coefficient values were 0.9917 and 0.9916 for girls, and 0.9886 and 0.9869 for boys. The sensitivity and specificity test has also shown high agreement. However, for girls, the sensitivity was higher for the specific variant (100% vs. 90.9%).

CONCLUSION

The results of the study show that allometric scaling of LVM for height can very reliably reproduce the results of LVM normalization for height based on the centile curves method. However, the analysis of sensitivity and specificity indicates greater agreement for the allometric normalization with the group-specific allometric exponents.

Left ventricular mass is underestimated in overweight children because of incorrect body size variable chosen for normalization

Background

Left ventricular mass normalization for body size is recommended, but a question remains: what is the best body size variable for this normalization—body surface area, height or lean body mass computed based on a predictive equation? Since body surface area and computed lean body mass are derivatives of body mass, normalizing for them may result in underestimation of left ventricular mass in overweight children. The aim of this study is to indicate which of the body size variables normalize left ventricular mass without underestimating it in overweight children.

Methods

Left ventricular mass assessed by echocardiography, height and body mass were collected for 464 healthy boys, 5–18 years old. Lean body mass and body surface area were calculated. Left ventricular mass z-scores computed based on reference data, developed for height, body surface area and lean body mass, were compared between overweight and non-overweight children. The next step was a comparison of paired samples of expected left ventricular mass, estimated for each normalizing variable based on two allometric equations—the first developed for overweight children, the second for children of normal body mass.

Results

The mean of left ventricular mass z-scores is higher in overweight children compared to non-overweight children for normative data based on height (0.36 vs. 0.00) and lower for normative data based on body surface area (-0.64 vs. 0.00). Left ventricular mass estimated normalizing for height, based on the equation for overweight children, is higher in overweight children (128.12 vs. 118.40); however, masses estimated normalizing for body surface area and lean body mass, based on equations for overweight children, are lower in overweight children (109.71 vs. 122.08 and 118.46 vs. 120.56, respectively).

Conclusion

Normalization for body surface area and for computed lean body mass, but not for height, underestimates left ventricular mass in overweight children.

Normal Values for Left Ventricular Mass in Relation to Lean Body Mass in Child and Adolescent Athletes

It has been demonstrated that regular sport activity in children leads to physiological changes in the heart including increased left ventricular (LV) myocardial thickness and mass (LVM). The aim of the study was to establish the first specific normal values of LVM for child and adolescent athletes. Parasternal long-axis, 2D-guided echocardiographic measurements were obtained from a group of 791 Caucasian child athletes (age 5-18 years, 58.7% boys). For the preparation of normative data, LVM-for-lean body mass (LBM) reference curves were constructed using the LMS method. Then, a simple correlation plot was constructed to analyse the concordant and discordant indications of left ventricular hypertrophy (LVH), defined as LVM-for-LBM above the 95th percentile, according to the newly created and previously published normative data on LVM-for-LBM in the general population of children. Reference scatter plots of LVM-for-LBM for boys and girls in the analysed group of children practicing sports were presented, showing mean values of LVM and z-scores. The application to the studied group of reference centiles established for the general population of children would lead to false positive misclassification of increased LVH in 5.8% of the girls and 17.0% of the boys. We present the first specific normative data for LV mass in relation to lean body mass in Caucasian children and adolescents engaged in regular sport activities. The application of specific normative data for LV mass results in fewer false positive findings of left ventricular hypertrophy in this group than that of reference values for general paediatric population.

Effects of obesity and metabolic syndrome on cardiovascular outcomes in pediatric kidney transplant recipients: a longitudinal study

BACKGROUND

Obesity and metabolic syndrome (MS) are common after kidney transplantation, but their contribution to adverse cardiovascular (CV) outcomes in children are not well known. A prospective, controlled, longitudinal cohort study was conducted to investigate the effects of obesity and MS on left ventricular hypertrophy (LVH) and myocardial strain in pediatric kidney transplant recipients.

METHODS

Transplant recipients (n = 42) had anthropometrics [body mass index (BMI), waist circumference, waist-to-height ratio], biochemical parameters (fasting glucose, lipid panel, HbA1c%), and echocardiogram with speckle tracking analysis for strain measured at 1, 18, and 30 months post-transplant. Additionally, 35 pre-transplant echocardiograms were analyzed retrospectively. Healthy children (n = 24) served as controls.

RESULTS

Waist-to-height ratio detected abdominal obesity in 46% of transplant patients, whereas only 8.1% were identified as obese by waist circumference. Ejection fraction and fractional shortening of the transplant group were normal. Prevalence of LVH was 35.2%, 17.1%, and 35.5% at 1, 18, and 30 months respectively. The longitudinal strain of transplant group was worse than controls at all time points (p < 0.001). Hemodialysis was independently associated with 21% worse longitudinal strain during the pre-transplant period (p = 0.04). After transplantation, obesity, MS, and systolic hypertension predicted increased odds of LVH (p < 0.04). Worse longitudinal strain was independently associated with obesity, MS, hypertension, and the combination of MS with elevated low density lipoprotein (LDL) cholesterol (p < 0.04), whereas higher estimated glomerular filtration rate (eGFR) conferred a protective effect (p < 0.001).

CONCLUSION

Obesity and MS adversely affect CV outcomes after transplantation. Further studies are needed to investigate speckle tracking echocardiography as a tool for early detection of subclinical myocardial dysfunction in this population.

No Obesity Paradox in Pediatric Patients With Dilated Cardiomyopathy

OBJECTIVES

This study aimed to examine the role of nutrition in pediatric dilated cardiomyopathy (DCM).

BACKGROUND

In adults with DCM, malnutrition is associated with mortality, whereas obesity is associated with survival.

METHODS

The National Heart, Lung, and Blood Institute-funded Pediatric Cardiomyopathy Registry was used to identify patients with DCM and categorized by anthropometric measurements: malnourished (MN) (body mass index [BMI] <5% for age ≥2 years or weight-for-length <5% for <2 years), obesity (BMI >95% for age ≥2 years or weight-for-length >95% for <2 years), or normal bodyweight (NB). Of 904 patients with DCM, 23.7% (n = 214) were MN, 13.3% (n=120) were obese, and 63.1% (n=570) were NB.

RESULTS

Obese patients were older (9.0 vs. 5.7 years for NB; p < 0.001) and more likely to have a family history of DCM (36.1% vs. 23.5% for NB; p = 0.023). MN patients were younger (2.7 years vs. 5.7 years for NB; p < 0.001) and more likely to have heart failure (79.9% vs. 69.7% for NB; p = 0.012), cardiac dimension z-scores >2, and higher ventricular mass compared with NB. In multivariable analysis, MN was associated with increased risk of death (hazard ratio [HR]: 2.06; 95% confidence interval [CI]: 1.66 to 3.65; p < 0.001); whereas obesity was not (HR: 1.49; 95% CI: 0.72 to 3.08). Competing outcomes analysis demonstrated increased risk of mortality for MN compared with NB (p = 0.03), but no difference in transplant rate (p = 0.159).

CONCLUSIONS

Malnutrition is associated with increased mortality and other unfavorable echocardiographic and clinical outcomes compared with those of NB. The same effect of obesity on survival was not observed. Further studies are needed investigating the long-term impact of abnormal anthropometric measurements on outcomes in pediatric DCM. (Pediatric Cardiomyopathy Registry; NCT00005391).

Relationship of Echocardiographic Z Scores Adjusted for Body Surface Area to Age, Sex, Race, and Ethnicity: The Pediatric Heart Network Normal Echocardiogram Database

BACKGROUND

Published nomograms of pediatric echocardiographic measurements are limited by insufficient sample size to assess the effects of age, sex, race, and ethnicity. Variable methodologies have resulted in a wide range of Z scores for a single measurement. This multicenter study sought to determine Z scores for common measurements adjusted for body surface area (BSA) and stratified by age, sex, race, and ethnicity.

METHODS AND RESULTS

Data collected from healthy nonobese children ≤18 years of age at 19 centers with a normal echocardiogram included age, sex, race, ethnicity, height, weight, echocardiographic images, and measurements performed at the Core Laboratory. Z score models involved indexed parameters (X/BSAα) that were normally distributed without residual dependence on BSA. The models were tested for the effects of age, sex, race, and ethnicity. Raw measurements from models with and without these effects were compared, and <5% difference was considered clinically insignificant because interobserver variability for echocardiographic measurements are reported as ≥5% difference. Of the 3566 subjects, 90% had measurable images. Appropriate BSA transformations (BSAα) were selected for each measurement. Multivariable regression revealed statistically significant effects by age, sex, race, and ethnicity for all outcomes, but all effects were clinically insignificant based on comparisons of models with and without the effects, resulting in Z scores independent of age, sex, race, and ethnicity for each measurement.

CONCLUSIONS

Echocardiographic Z scores based on BSA were derived from a large, diverse, and healthy North American population. Age, sex, race, and ethnicity have small effects on the Z scores that are statistically significant but not clinically important.

Cardiovascular effects of metabolic syndrome after transplantation: convergence of obesity and transplant-related factors

Children are at increased risk of developing metabolic syndrome (MS) after kidney transplantation, which contributes to long-term cardiovascular (CV) morbidities and decline in allograft function. While MS in the general population occurs due to excess caloric intake and physical inactivity, additional chronic kidney disease and transplant-related factors contribute to the development of MS in transplant recipients. Despite its significant health consequences, the interplay of the individual components in CV morbidity in pediatric transplant recipients is not well understood. Additionally, the optimal methods to detect early CV dysfunction are not well defined in this unique population. The quest to establish clear guidelines for diagnosis is further complicated by genetic differences among ethnic groups that necessitate the development of race-specific criteria, particularly with regard to individuals of African descent who carry the apolipoprotein L1 variant. In children, since major CV events are rare and traditional echocardiographic measures of systolic function, such as ejection fraction, are typically well preserved, the presence of CV disease often goes undetected in the early stages. Recently, new noninvasive imaging techniques have become available that offer the opportunity for early detection. Carotid intima-media thickness and impaired myocardial strain detected by speckle tracking echocardiography or cardiac magnetic resonance are emerging as early and sensitive markers of subclinical CV dysfunction. These highly sensitive tools may offer the opportunity to elucidate subtle CV effects of MS in children after transplantation. Current knowledge and future directions are explored in this review.

Velocity vector imaging shows normal cardiac systolic function in survivors of severe bronchopulmonary dysplasia at six to 16 years of age

AIM

This study evaluated global myocardial function and associations between cardiac function and lung function in very low birth weight (VLBW) children, with and without severe radiographic bronchopulmonary dysplasia (BPD), at six to 14 years of age.

METHODS

We studied 34 VLBW and 19 term-born controls, and the VLBW group was further divided into a BPD group with severe radiographic BPD and those without radiographic BPD in infancy. Detailed right and left ventricular myocardial functions were analysed by velocity vector imaging, and the left ventricular mass was calculated. The associations between cardiac function and lung function were assessed by impulse oscillometry.

RESULTS

The right and left ventricular myocardial systolic functions and the left ventricular mass were similar in the three groups. Lung function was not associated with cardiac systolic function. Neonatal exposure to dexamethasone treatment was negatively associated with right ventricular function, as measured by the automated fractional area change, with an odds ratio of 7.9 and 95% confidence interval of 1.9-33.5 (p = 0.005).

CONCLUSION

Lung function measurements were not associated with cardiac systolic function in preterm infants at six to 14 years of age. Neonatal exposure to dexamethasone, used for weaning from the ventilator, was negatively associated with right ventricular function.

Normative Left Ventricular M-Mode Echocardiographic Values in Preterm Infants up to 2 kg

BACKGROUND

There is a paucity of normative echocardiographic data in preterm infants. The objectives of this study were to (1) derive left ventricular (LV) M-mode reference values and (2) compare the performance of alternative methods of indexing LV dimensions and LV mass (LVM) in preterm infants. The authors propose that indexing LV measures to weight in preterm infants is a practical approach given the variability associated with tape-measure length measurement in infants.

METHODS

In this retrospective study, LV M-mode echocardiographic measurements of end-diastolic interventricular septal thickness, end-diastolic LV posterior wall thickness, LV end-diastolic and end-systolic dimensions, LVM, and relative wall thickness were remeasured in 503 hospitalized preterm infants ≤2 kg (372 from a retrospective sample and 131 prospectively enrolled). Measures for all variables did not differ between retrospective and prospective samples, so results were pooled. LV dimensions and LVM indexed for weight, length, and body surface area sex-specific centile curves and corresponding Z scores were generated using Cole's lambda-mu-sigma method. Threshold limits (10th and 80th percentiles) were used to generate the normative range for relative wall thickness.

RESULTS

Sex-specific centile curves using LVM, end-diastolic interventricular septal thickness, end-diastolic LV posterior wall thickness, LV end-diastolic dimension, and LV end-systolic dimension indexed to weight were similar to the curves generated using length and body surface area. The mean normal range for relative wall thickness was 0.33 (10th percentile, 0.26; 80th percentile, 0.38).

CONCLUSIONS

From this large cohort of preterm infants, LV M-mode dimension and LVM centile curves indexed to weight were developed as a practical method to assess LV morphology in preterm infants.

Cardiovascular Disease Risk Factors and Left Ventricular Hypertrophy in Girls and Boys With CKD

BACKGROUND AND OBJECTIVES

Prior studies suggested that women with CKD have higher risk for cardiovascular disease (CVD) and mortality than men, although putative mechanisms for this higher risk have not been identified. We assessed sex differences in (1) CVD risk factors and left ventricular hypertrophy (LVH), and (2) the relationship of left ventricular mass (LVM) with different measures of body size in children with CKD.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

The study population comprised 681 children with CKD from the Chronic Kidney Disease in Children cohort, contributing 1330 visits. CVD risk factors were compared cross-sectionally by sex. LVH was defined as LVM/height2.7 >95th percentile and LVM relative to estimated lean body mass (eLBM) >95th percentile for age and sex. Differences in LVM by sex were assessed by adjusting for age, weight, height, and eLBM using bivariate and multivariate regression models.

RESULTS

Girls were less likely to have uncontrolled hypertension (26% versus 38%, P=0.001), had lower diastolic BP z-scores (+0.3 versus +0.6, P=0.001), and had lower prevalence of high triglycerides (38% versus 47%, P=0.03) compared with boys. When LVH was defined by LVM indexed to height, girls had higher prevalence of LVH (16% versus 9%, P=0.01); when LVH was defined by LVM relative to eLBM, prevalence of LVH was similar between girls and boys (18% versus 17%, P=0.92). In regression models adjusting for eLBM, no sex differences in LVM were observed.

CONCLUSIONS

Despite lack of increased prevalence of CVD risk factors, indexing LVM to height showed a higher proportion of LVH among girls, while estimates of LVH based on eLBM showed no sex differences. Indexing LVM to eLBM may be an alternative to height indexing in children with CKD.

The Prevalence of Left Ventricular Hypertrophy in Obese Children Varies Depending on the Method Utilized to Determine Left Ventricular Mass

Obesity and left ventricular hypertrophy (LVH) have been identified as independent risk factors for cardiovascular events. The definition of LVH depends on the geometric algorithm used to calculate LV mass (LVM) by echocardiography and the method used to normalize LVM for body size. This study evaluates the effect of these methods on the prevalence of LVH in obese children. LVM for 109 obese and 109 age-matched non-obese children was calculated using M-mode or two-dimensional echocardiography (2DE). LVM was then normalized to height 2.7 as indexed LVM (LVMI), to body surface area (BSA), height, and lean body mass (LBM) as LVM Z-scores. LVH was defined as LVMI >95th ‰ using age-specific normal reference values or LVM Z-scores ≥2. The prevalence of LVH by LVMI and LVM Z-scores was compared. There was a correlation between LVM determined by M-mode and by 2DE (R (2) = 0.91), although M-mode LVM was greater than 2DE LVM. However, the difference between these values was greater in obese children than in non-obese children. Based on the method of normalization, the prevalence of LVH among obese children was 64 % using LVMI, 15 % using LVM Z-scores for height, 8 % using LVM Z-scores for BSA and 1 % using LVM Z-scores for LBM. Height-based normalization correlates with obesity and hypertension. The methods used to measure and normalize LVM have a profound influence on the diagnosis of LVH in obese children. Further study is needed to determine which method identifies children at risk for cardiovascular morbidity and mortality.

The Impact of Aortic Valve Replacement on Left Ventricular Remodeling in Children

There are scant data in pediatrics on the optimal timing for aortic valve repair (AVR). This study assesses the midterm response to AVR and possible predictors of poor outcome. From 2001 to 2006, 41 patients had greater than 3-month follow-up after AVR for aortic insufficiency, aortic stenosis, or both. Pre-, peri-, and post-operative data were collected, including demographics and clinical symptoms. Two reviewers measured echocardiographic parameters from the pre-operative and latest follow-up echocardiograms. Ventricular dimensions were indexed to body surface area (z-score). Median age at AVR was 13 years with 83 % having a Ross operation. The average left ventricular end-diastolic dimension pre-op, z-score of +1.3, significantly decreased at last follow-up to a mean z-score of -0.1 (p < 0.001). Similarly the indexed LV mass decreased from +3.9 to +0.5 (p < 0.001). There was no significant correlation between the presence of pre-op symptoms and the presence of post-op LV dilatation, hypertrophy, or dysfunction. In the subset of patients (7/41) with persistent LV dysfunction at last follow-up, there was a significant correlation with pre-op LV dilatation as assessed by both LVEDD (p = 0.02) and LVESD (p = 0.05). Children demonstrate significant reverse remodeling after AVR. Pre-op LV dilatation may predict patients with persistent LV dysfunction post-AVR. Symptoms are less useful in children, suggesting the need for more objective data for functional assessment.

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.

Left Ventricular Mass Indexing in Infants, Children, and Adolescents: A Simplified Approach for the Identification of Left Ventricular Hypertrophy in Clinical Practice

OBJECTIVE

To determine a simplified method to identify presence of left ventricular hypertrophy (LVH) in pediatric populations because the relationship between heart growth and body growth in children has made indexing difficult for younger ages.

STUDY DESIGN

Healthy children (n = 400; 52% boys, 0-18 years of age) from 2 different European hospitals were studied to derive a simplified formula. Left ventricular mass (LVM) was calculated according to the Devereux formula. The derived approach to index LVM was tested on a validation cohort of 130 healthy children from a different hospital center.

RESULTS

There was a strong nonlinear correlation between height and LVM. LVM was best related to height to a power of 2.16 with a correction factor of 0.09. Analysis of residuals for LVM/[(height(2.16)) + 0.09] showed an homoscedastic distribution in both sexes throughout the entire height range. A partition value of 45 g/m(2.16) was defined as the upper normal limit for LVM index. As opposed to formula suggested by current guidelines (ie, LVM/height(2.7)) when applying the proposed approach in the validation cohort of 130 healthy participants, no false positives for LVH were found (0% vs 8%; P < .01).

CONCLUSIONS

Our data support the possibility to have a single partition (ie, 45 g/m(2.16)) value across the whole pediatric age range to identify LVH, without the time-consuming need of computing specific percentiles for height and sex.

New Reference Centiles for Left Ventricular Mass Relative to Lean Body Mass in Children

BACKGROUND

Echocardiographic measurement of left ventricular (LV) mass is routinely performed in pediatric patients with elevated cardiovascular risk. The complex relationship between heart growth and body growth in children requires normalization of LV mass to determine its appropriateness relative to body size. LV mass is strongly determined by lean body mass (LBM). Using new LBM predictive equations, the investigators generated sex-specific LV mass-for-LBM centile curves for children 5 to 18 years of age.

METHODS

This retrospective study used M-mode echocardiographic data collected from 1995 through 2003 from 939 boys and 771 girls between 5 and 18 years of age (body mass index < 85th percentile for sex and age) to create smoothed sex-specific LV mass-for-LBM reference centile curves using the Lamda Mu Sigma method. The newly developed reference centiles were applied to children with essential hypertension and with chronic kidney disease, groups known to be at high risk for LV hypertrophy (LVH). The identification of LVH using two different normalization approaches was compared: LV mass-for-LBM and LV mass index-for-age percentiles.

RESULTS

Among 231 children at risk for LVH, on average, relative LV mass was higher using the LV mass index-for-age percentile method than the LV mass-for-LBM percentile method. LVH was more likely to be diagnosed among overweight children and less likely among thin children.

CONCLUSIONS

This study provides new LV mass reference centiles expressing LV mass relative to LBM, the strongest determinant of LV mass. These reference centiles may allow more accurate stratification of cardiovascular risk in children.

Cardiac structure and function in adolescent Sherpa; effect of habitual altitude and developmental stage

The purpose of this study was to examine ventricular structure and function in Sherpa adolescents to determine whether age-specific differences in oxygen saturation (SpO2 ) and pulmonary artery systolic pressure (PASP) influence cardiac adaptation to chronic hypoxia early in life. Two-dimensional, Doppler, and speckle-tracking echocardiography were performed on adolescent (9-16 yr) highland Sherpa (HLS; 3,840 m; n = 26) and compared with age-matched lowland Sherpa (LLS; 1,400 m; n = 10) and lowland Caucasian controls (LLC; sea level; n = 30). The HLS were subdivided into pre- and postadolescence; SpO2 was also recorded. Only HLS exhibited a smaller relative left ventricular (LV) end-diastolic volume; however, both HLS and LLS demonstrated a lower peak LV untwisting velocity compared with LLC (92 ± 26 and 100 ± 45 vs. 130 ± 43°/s, P < 0.05). Although SpO2 was similar between groups, PASP was higher in post- vs. preadolescent HLS (30 ± 5 vs. 25 ± 5 mmHg, P < 0.05), which negatively correlated with right ventricular strain rate (r = 0.50, P < 0.01). Much like their adult counterparts, HLS and LLS adolescents exhibit slower LV diastolic relaxation, despite residing at different altitudes. These findings suggest fundamental differences exist in the diastolic function of Sherpa that are present at an early age and may be retained after migration to lower altitudes. The higher PASP in postadolescent Sherpa is in contrast to previous reports of lowland children at high altitude and, unlike that in lowlanders, was not explained by differences in SpO2 ; thus different regulatory mechanisms seem to exist between these two distinct populations.

Echocardiographic Characteristic Of Left Ventricular Geometry Of 12-17 Years Athletes

Aim. To compare the type of left ventricular geometry associated with training among 12-17 years athletes currently competing in cycling, rowing and basketball playing and to determine the factors influencing left ventricular geometry. Methods. A total 167 male athletes 12-17 year-old, involved in basketball (n = 62), academic rowing (n =51) and cycling (n = 54) and 168 sedentary non-athletes, matched for age and sex were involved in this study. All participants underwent twodimensional, M-mode and Doppler echocardiography. To estimate left ventricular geometry relative wall thickness and left ventricular mass index were calculated. Left ventricular geometry was assessed as normal, eccentric ventricular hypertrophy, concentric left ventricular hypertrophy, concentric left ventricular remodeling. Results. Left ventricular hypertrophy was present in 48 % of all athletes, predominantly (34 %) eccentric hypertrophy. 16% of athletes had concentric hypertrophy. Only 7% of athletes manifested concentric remodeling. The prevalence of eccentric hypertrophy was more common in cyclists (54%), concentric hypertrophy was more frequent in rowers (38%), and normal left ventricular geometry was more common in basketball players (53%). Multivariate regression analysis showed that age was the important determinant of eccentric and concentric left ventricular hypertrophy. Eccentric left ventricular hypertrophy also was independently associated to training volume (hour per week) and cycling sporting discipline. Conclusion. Almost half of athletes (48%) had left ventricular hypertrophy, predominantly eccentric hypertrophy, and the age was the important determinant of left ventricular hypertrophy (eccentric and concentric). Training volume and cycling sporting discipline were significantly associated with eccentric left ventricular hypertrophy.

Sex-specific lean body mass predictive equations are accurate in the obese paediatric population

BACKGROUND

The clinical assessment of lean body mass (LBM) is challenging in obese children. A sex-specific predictive equation for LBM derived from anthropometric data was recently validated in children.

AIM

The purpose of this study was to independently validate these predictive equations in the obese paediatric population.

SUBJECTS AND METHODS

Obese subjects aged 4-21 were analysed retrospectively. Predicted LBM (LBMp) was calculated using equations previously developed in children. Measured LBM (LBMm) was derived from dual-energy x-ray absorptiometry. Agreement was expressed as [(LBMm-LBMp)/LBMm] with 95% limits of agreement.

RESULTS

Of 310 enrolled patients, 195 (63%) were females. The mean age was 11.8 ± 3.4 years and mean BMI Z-score was 2.3 ± 0.4. The average difference between LBMm and LBMp was -0.6% (-17.0%, 15.8%). Pearson's correlation revealed a strong linear relationship between LBMm and LBMp (r = 0.97, p < 0.01).

CONCLUSION

This study validates the use of these clinically-derived sex-specific LBM predictive equations in the obese paediatric population. Future studies should use these equations to improve the ability to accurately classify LBM in obese children.

The effects of sports participation on the development of left ventricular mass in adolescent boys

OBJECTIVES

To examine the contribution of body size, biological maturation, and nonelite sports participation to longitudinal changes of left ventricular mass (LVM) in healthy boys.

METHODS

One hundred and ten boys (11.0-14.5 years at baseline) were assessed biannually for 2 years. Stature, body mass, and four skinfolds were measured. Lean body mass (LBM) was estimated. Biological maturation was assessed as years from age at peak height velocity (APHV). Sports participation was assessed by questionnaire. LVM was obtained from M-mode echocardiograms using two-dimensional images. To account for the repeated measures within individual nature of longitudinal data, multilevel random effects regression analyses were used in the analysis.

RESULTS

LVM increased on average 42 ± 18 g from 11 to 15 years (P < 0.05) and 76 ± 14 g from 3.5 years pre-APHV to 1.5 years post-APHV (P < 0.05). The multilevel model with the best statistical fit (Model B) showed that changes of 1 cm in stature, 1 year post-APHV, and 1 kg of LBM predicts 4.7, 0.5, and 1 g of LVM (P < 0.05), respectively.

CONCLUSIONS

Among healthy, male adolescents aged 11-15 years individual differences in growth and biological maturation influence growth of LVM. Subcutaneous adiposity and sports participation were not associated with greater LVM.

Bias related to body mass index in pediatric echocardiographic Z scores

In pediatric echocardiography, cardiac dimensions are often normalized for weight, height, or body surface area (BSA). The combined influence of height and weight on cardiac size is complex and likely varies with age. We hypothesized that increasing weight for height, as represented by body mass index (BMI) adjusted for age, is poorly accounted for in Z scores normalized for weight, height, or BSA. We aimed to evaluate whether a bias related to BMI was introduced when proximal aorta diameter Z scores are derived from bivariate models (only one normalizing variable), and whether such a bias was reduced when multivariable models are used. We analyzed 1,422 echocardiograms read as normal in children ≤18 years. We computed Z scores of the proximal aorta using allometric, polynomial, and multivariable models with four body size variables. We then assessed the level of residual association of Z scores and BMI adjusted for age and sex. In children ≥6 years, we found a significant residual linear association with BMI-for-age and Z scores for most regression models. Only a multivariable model including weight and height as independent predictors produced a Z score free of linear association with BMI. We concluded that a bias related to BMI was present in Z scores of proximal aorta diameter when normalization was done using bivariate models, regardless of the regression model or the normalizing variable. The use of multivariable models with weight and height as independent predictors should be explored to reduce this potential pitfall when pediatric echocardiography reference values are evaluated.

Morfologia do ventrículo esquerdo em adolescentes: comparação entre atletas e não atletas

Introdução: A morfologia do ventrículo esquerdo altera-se com o crescimento e desenvolvimento, durante a infância e adolescência. Contudo, são escassos os estudos comparativos entre não atletas e jovens atletas de elite.Objetivo: Analisar possíveis diferenças na morfologia do ventrículo esquerdo entre jovens atletas de elite e não atletas, do sexo masculino.Métodos: Trinta atletas de elite (15,4±0,6 anos; 68,0±11,3 kg; 175,2±7,5 cm) e 28 adolescentes saudáveis sem experiência com a prática esportiva (15,2±1,3 anos; 62,9± 3,8 kg; 168,8±7,7 cm) foram submetidos a medidas antropométricas (estatura, massa corporal e espessura de dobras cutâneas) e avaliações ecocardiográficas.Resultados: Diferenças estatisticamente significantes foram encontradas nos diâmetros telediastólico e telesistólico do ventrículo esquerdo, na espessura do septo interventricular em diástole, na espessura da parede posterior do ventrículo esquerdo, no diâmetro do átrio esquerdo e na relação entre o diâmetro do átrio esquerdo e o diâmetro da raiz da aorta, com os jovens atletas de elite apresentando valores superiores aos não atletas (P<0,01), mesmo após ajuste pela estatura. Correlações positivas e de moderada magnitude entre a massa do ventrículo esquerdo e a estatura foram encontradas em atletas (r=0,57) e não atletas (r=0,40).Conclusão: Os resultados do presente estudo sugerem que os valores superiores nas medidas da cavidade e de espessura da parede ventricular esquerda, encontrados no coração de jovens atletas de elite não podem ser explicados pela maior estatura, destacando a importância da exploração de modelos alométricos simples e multiplicativos que integrem medidas de maturação biológica em futuras investigações.

Myocardial atrophy in children with mitochondrial disease and Duchenne muscular dystrophy

Purpose

Mitochondrial disease (MD) and Duchenne muscular dystrophy (DMD) are often associated with cardiomyopathy, but the myocardial variability has not been isolated to a specific characteristic. We evaluated the left ventricular (LV) mass by echocardiography to identify the general distribution and functional changes of the myocardium in patients with MD or DMD.

Methods

We retrospectively evaluated the echocardiographic data of 90 children with MD and 42 with DMD. Using two-dimensional echocardiography, including time-motion (M) mode and Doppler measurements, we estimated the LV mass, ratio of early to late mitral filling velocities (E/A), ratio of early mitral filling velocity to early diastolic mitral annular velocity (E/Ea), stroke volume, and cardiac output. A "z score" was generated using the lambda-mu-sigma method to standardize the LV mass with respect to body size.

Results

The LV mass-for-height z scores were significantly below normal in children with MD (-1.02±1.52, P<0.001) or DMD (-0.82±1.61, P=0.002), as were the LV mass-for-lean body-mass z scores. The body mass index (BMI)-for-age z scores were far below normal and were directly proportional to the LV mass-for-height z scores in both patients with MD (R=0.377, P<0.001) and those with DMD (R=0.330, P=0.033). The LV mass-for-height z score correlated positively with the stroke volume index (R=0.462, P<0.001) and cardiac index (R=0.358, P<0.001).

Conclusion

LV myocardial atrophy is present in patients with MD and those with DMD and may be closely associated with low BMI. The insufficient LV mass for body size might indicate deterioration of systolic function in these patients.

Lean body mass may explain apparent racial differences in carotid intima-media thickness in obese children

BACKGROUND

Racial differences in carotid intima-media thickness (cIMT) have been suggested to be associated with the disproportionally high prevalence of cardiovascular disease in black adults. The objective of this study was to evaluate the effects of cardiovascular risk factors on the racial differences seen in cIMT in obese children.

METHODS

Obese subjects aged 4 to 21 years were recruited prospectively. Height, weight, blood pressure, fasting insulin, glucose, lipid panel, high-sensitivity C-reactive protein, and body composition by dual-energy x-ray absorptiometry were obtained. B-mode carotid imaging was analyzed by a single blinded physician.

RESULTS

A total of 120 subjects (46 white, 74 black) were enrolled. Black subjects exhibited greater cIMT (0.45 ± 0.03 vs 0.43 ± 0.02 cm, P < .01) and higher lean body mass index (19.3 ± 3.4 vs 17.3 ± 3.2 kg/m², P = .02) than white subjects. Simple linear regression revealed modest associations between mean cIMT and race (R = 0.52, P < .01), systolic blood pressure (R = 0.47, P < .01), and lean body mass (R = 0.51, P < .01). On multivariate regression analysis, lean body mass remained the only measure to maintain a statistically significant relationship with mean cIMT (P < .01).

CONCLUSIONS

Black subjects demonstrated greater cIMT than white subjects. The relationship between race and cIMT disappeared when lean body mass was accounted for. Future studies assessing the association of cardiovascular disease risk factors to cIMT in obese children should include lean body mass in the analysis.

Left ventricular mass in children and adolescents with elevated body mass index and normal waist circumference

Children and adolescents with elevated body mass index (BMI) who have normal waist circumference (NWC) have a cardiometabolic risk profile similar to normal children. However, there is a lack of adequate information regarding their left ventricular mass (LVM). The present study was undertaken to evaluate LVM in children with elevated BMI with NWC. LVM was assessed by echocardiography in 247 children (age 2 to 19 years) without evidence of heart disease. Data on those who had elevated BMI with NWC (group 1, n = 80) were compared with matched normal controls with normal BMI who had NWC (group 2, n = 80) and children with elevated BMI with increased waist circumference (IWC; group 3, n = 87). Correlations, t tests, and linear regressions were used for statistical testing. LVM in children with elevated BMI with NWC was not significantly different from normal controls (97.6 ± 44.4 vs 100.7 ± 47.9 g, p = 0.6713, respectively); however, it was significantly less than that in subjects with elevated BMI who also had IWC (97.6 ± 44.4 vs 114.5 ± 47.8 g, p = 0.0193, respectively). Similar to normal controls, those subjects with elevated BMI with NWC had a stronger correlation between LVM and lean body mass (R(2) = 0.86 and 0.86, respectively) than subjects with elevated BMI with IWC (R(2) = 0.75). In conclusion, children with elevated BMI with NWC appear to have a similar LVM profile as children with normal BMI with NWC. The present study emphasizes the importance of measuring waist circumference in children with elevated BMI.

Scaling left ventricular mass in adolescent boys aged 11-15 years

BACKGROUND

Normalizing left ventricular mass (LVM) for inter-individual variation in body size is a central issue in human biology. During the adolescent growth spurt, variability in body size descriptors needs to be interpreted in combination with biological maturation.

AIM

To examine the contribution of biological maturation, stature, sitting height, body mass, fat-free mass (FFM) and fat mass (FM) to inter-individual variability in LVM in boys, using proportional allometric modelling.

SUBJECTS AND METHODS

The cross-sectional sample included 110 boys of 11-15 years (12.9-1.0 years). Stature, sitting height, body mass, cardiac chamber dimensions and LVM were measured. Age at peak height velocity (APHV) was predicted and used as an indicator of biological maturation. Percentage fat was estimated from triceps and subscapular skinfolds; FM and FFM were derived.

RESULTS

Exponents for body size descriptors were k = 2.33 for stature, k = 2.18 for sitting height, k = 0.68 for body mass, k = 0.17 for FM and k = 0.80 for FFM (adjusted R(2 )= 19-62%). The combination of body descriptors and APHV increased the explained variance in LVM (adjusted R(2)( )= 56-69%).

CONCLUSION

Stature, FM and FFM are the best combination for normalizing LVM in adolescent boys; when body composition is not available, an indicator of biological maturity should be included with stature.