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.
This investigation was undertaken to answer 3 basic questions in children and adolescents who have elevated body mass index (BMI), both overweight and obese with normal waist circumference (NWC; the study group): (1) Is the left ventricular mass (LVM) in the “study group” similar to the group with normal BMI of similar age, gender, and waist circumference (WC)? (2) Is the LVM in the study group similar to the group who have elevated BMI and increased waist circumference (IWC)? and (3) How does LVM correlate with BMI, WC, and lean body mass (LBM) in the study group compared with the groups who have normal BMI with NWC and who have elevated BMI with IWC?
Methods
The total study group comprised 247 subjects. The primary study group of 80 subjects had elevated BMI with NWC (group 1). Their LVM data were compared with an equal number of randomly selected subjects (n = 80) from a pool of 388 subjects with normal BMI who had NWC matched for WC, age, and gender with the help of a software (normal matched controls, group 2). LVM from subjects in group 1 were also compared with 87 subjects who had elevated BMI with IWC (group 3).
The aforementioned groups of 247 patients were selected from a total of 562 subjects, all of whom were evaluated by a pediatric cardiologist at a community hospital from August 2005 to March 2013. Primary referral diagnoses in the studied patients included heart murmur (n = 157), chest pain (n = 115), dizziness and syncope (n = 102), palpitations (n = 80), family history of heart disease (n = 28), abnormal electrocardiogram (n = 22), and miscellaneous other reasons (n = 58). After evaluation, all presenting symptoms were found to be noncardiac (noncardiac chest pain, nonparoxysmal caffeine-related palpitations, and neurocirculatory dizziness and syncope). Heart murmurs were innocent murmurs. Children who had suspected or documented cardiac pathology based on history, clinical evaluation, electrocardiography, and 2-dimensional and Doppler echocardiographies were excluded and were not part of the aforementioned total sample of 562 subjects. Every effort was made to include only subjects with no evidence of cardiac abnormality (n = 562).
Elevated BMI was defined as BMI greater than or equal to eighty-fifth percentile for age and gender or BMI ≥25 kg/m 2 . Conversely, BMI less than eighty-fifth percentile for age and gender was considered a normal BMI. Central obesity was defined as WC more than ninetieth percentile for age, gender, and race (IWC), whereas WC less than or equal to ninetieth percentile for age, gender, and race was considered NWC.
Of the 562 subjects without evidence of cardiac disease, 80 children were identified has having elevated BMI who had NWC (the study group). Three hundred eighty eight of 562 subjects had normal BMI with NWC: 218 of 388 were boys (mean age 10.5 ± 4.9 years, mean BMI = 17.9 ± 2.6 kg/m 2 , WC = 63.7 ± 12 cm), whereas 170 of 388 were girls (mean age 11.3 ± 5 years, mean BMI = 18.2 ± 2.9 kg/m 2 , WC = 67.2 ± 13 cm). The mean BMI and WC of these 388 subjects were consistent with reference values (from fiftieth to sixtieth percentile). Mean Z scores for LVM-for-height percentile curves were below the expected zero, and all the values were <1.87, with a normal Gaussian distribution (SD of 1.06). Seven children (7 of 562) who had normal BMI with IWC were not included in the final analysis because of small sample size. The remaining 87 of 562 children had elevated BMI with IWC.
To answer the 3 study questions listed in the first paragraph, 247 of 562 subjects were divided into following 3 groups: (1) group 1 (n = 80), subjects who had elevated BMI with NWC—the study group, (2) group 2 (n = 80 of 388), subjects who had normal BMI with NWC were randomly matched (for equal number) with the help of a software with the subjects in group 1 (n = 80) for WC, age, and gender (normal matched controls), and (3) group 3 (n = 87), subjects who had elevated BMI with IWC.
All subjects had body weight (kilogram), height (centimeter), heart rate, respiratory rate, and blood pressure (mm Hg) measured by a cardiac nurse. Blood pressures (BPs) at rest were taken with a sphygmomanometer in the right arm with the subject comfortably seated, their legs hanging, and their right arm at heart level with the appropriate size cuff. Patients were allowed 5 to 15 minutes to settle down before the BP was measured. An average of 3 BP measurements was taken only if the initial BP were more than ninetieth percentile for age, gender, and height. Diastolic BP was measured at phase V of the Korotkoff sound. The body surface area (BSA) was calculated using the method by Haycock et al, which has been shown to be the most appropriate method. Each subject underwent clinical evaluation by the investigator.
Based on the Center for Disease Control and Prevention guidelines, WC was measured to the nearest 0.1 cm with the subject in a standing position. The measurement was made with a standard measuring tape, just above the superolateral border of the right and left iliac crests. Measurements were obtained during subject exhalation, and the measuring tape remained parallel to the floor on all sides. The tape was then tightened slightly to make it snug without compressing the skin and underlying subcutaneous tissues. LBM was calculated based on the predictive equations validated for boys and girls that included natural logarithmic function of height and weight, Z scores of BMI, and age. Lean body mass index (LBMI) was calculated by correcting LBM for height similar to the weight correction done for BMI calculations. Non-LBMI was the difference between BMI and LBMI.
Two-dimensional, color flow Doppler, and spectral Doppler echocardiographies were performed with a commercially available ultrasound system (Sonos 5500 or IEE 33; Philips Medical System, Andover, Massachusetts) with the subjects in the supine and left lateral decubitus positions. All measurements were made according to the standard recommended laboratory protocol. In the present study, 2-dimensionally guided M-mode measurements were made by well-trained pediatric sonographers during end-diastole and end-systole for the interventricular septum, the left ventricular (LV) dimension, and for the LV posterior wall from a parasternal long-axis and parasternal short-axis views at the level of the tips of the papillary muscles using the leading-edge-to-leading-edge technique. No assessment was made for intra- or interobserver variability for any of the reported parameters.
LVM was indexed to BSA, height in meters raised to the 2.7 power, and height in meters raised to the 1.7 power. Z scores, based on LVM-for-height percentile curves, were calculated according to data published by Foster et al. Absolute LVM was calculated during diastole (LVM = 0.8× {1.04 [(LV internal diameter + posterior wall thickness + septal thickness) 3 − (LV internal diameter) 3 ]} + 0.6 g) based on the Guidelines by the Standards Committees. Z scores of LVM based on the LBM were calculated according to data published by Foster et al.
The primary independent variables were BMI, WC, and LBM. The dependent variables, calculated from echocardiographic measurements, in this study were LVM, LVM/height 2.7 , LVM/BSA, and LVM/height 1.7 . Age, systolic BP, diastolic BP, and BSA were considered as potential confounders. Simple linear regression was used to assess associations with BMI, WC, LBM, systolic and diastolic BPs, and LVM parameters. The variables of interest were compared among the 3 groups by an analysis of variance. Statistical significance was defined a priori as a p <0.05. The data are presented as mean and SD. The study was approved by the institutional review board.
Results
Patient demographics, LBM, and LVM parameters as measured by echocardiography among 3 groups (n = 247) are listed in Table 1 . LVM in children with elevated BMI with NWC was not significantly different from normal controls. It was significantly less than that in subjects with elevated BMI with IWC. Table 2 lists correlation data between LVM and BSA, BMI, WC, LBM, and systolic and diastolic BPs among 3 study groups of children and adolescents.
| Clinical and Echocardiographic Parameters | Elevated BMI With NWC (n = 80) | Normal BMI With NWC (n = 80) | Elevated BMI With IWC (n = 87) | p Value |
|---|---|---|---|---|
| Age (yrs) | 10.3 ± 4.6 | 11.2 ± 4.3 | 11 ± 4 | 0.3883 |
| Girl:boy | 31:49 | 31:49 | 44:43 | 0.2002 |
| Height (cm) | 139.1 ± 25 | 146.2 ± 27 | 146.4 ± 24 | 0.1118 |
| Weight (kg) | 43.8 ± 21 | 42.9 ± 19 | 58.1 ± 25 | <0.0001 ∗ † |
| BMI (kg/m 2 ) | 20.9 ± 3.2 | 18.7 ± 2.6 | 25.4 ± 4.5 | <0.0001 ∗ † ‡ |
| WC | 70.5 ± 13 | 69.3 ± 13 | 86.9 ± 17 | <0.0001 ∗ † |
| Systolic BP (mm Hg) | 106 ± 11 | 107 ± 12 | 111 ± 12 | 0.0074 ∗ † |
| Diastolic BP (mm Hg) | 61 ± 7 | 60 ± 8 | 63 ± 9 | 0.0342 † |
| LVM (g) | 97.6 ± 44.4 | 100.7 ± 47.9 | 114.5 ± 47.8 | 0.0456 ∗ |
| LVM/BSA (g/m 2 ) | 73.8 ± 13.4 | 74.4 ± 15.5 | 73.6 ± 14.2 | 0.9357 |
| LVM/height 2.7 (g/m 2.7 ) | 38.5 ± 7 | 34.4 ± 6.6 | 39.6 ± 7.9 | <0.0001 † ‡ |
| LVM/height 1.7 (g/m 1.7 ) | 52.8 ± 10.7 | 49.8 ± 11 | 57.3 ± 12.6 | <0.0002 ∗ † |
| LBM (kg) | 29.9 ± 15 | 31.5 ± 15 | 36.6 ± 16 | 0.0139 ∗ † |
| LVM/LBM | 3.4 ± 0.6 | 3.3 ± 0.6 | 3.3 ± 0.6 | 0.2287 |
| LBMI (kg/m 2 ) | 14.2 ± 2.4 | 13.6 ± 2.1 | 15.9 ± 2.9 | <0.0001 ∗ † |
| Non-LBMI (kg/m 2 ) | 6.8 ± 1.3 | 5.1 ± 1.1 | 9.5 ± 2.1 | <0.0001 ∗ † ‡ |
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
