ABSTRACT
BACKGROUND: Impaired subclinical ventricular function may contribute to the risk of cardiovascular disease in obesity. AIMS: The aim of this study was to determine the influence of obesity on left ventricular (LV) longitudinal myocardial function in normotensive obese children using two-dimensional (2D) speckle tracking echocardiography (STE). STUDY DESIGN: Case-control study. METHODS: Sixty normotensive obese children aged 10-16 years (mean age, 13.9±2.3 years) were compared with 50 normal-weight controls. Obese participants had a body mass index (BMI)≥95(th) percentile. Regional strain/strain rate (SR) values were compared with left ventricular (LV) parameters. The correlation was studied by linear regression analysis. RESULTS: Obese subjects exhibited a significantly higher LV end-diastolic diameter, left atrium/aortic diameter ratio, and LV mass/index when compared to controls (p<0.001). Left ventricular ejection fraction and regional systolic myocardial velocities were similar in the obese and control groups. By 2D STE, regional strain of both the septal wall (average strain: -16.0±3.9% vs -21.9±2.4%, p<0.001) and lateral wall (average strain: -15.6±2.3% vs -22.9±3.5%, p<0.001); regional SR of both the septal wall (average SRsys: -0.7±0.22 s(-1) vs -1.3±0.32 s(-1), p<0.001) and lateral wall (average SRsys: -0.67±0.19 s(-1) vs -1.33±0.31 s(-1), p<0.001); regional SRE/A of both the septal wall (average SRE/A: 1.8±0.83 vs. 2.2±0.91, p: 0.004) and lateral wall (average SRE/A: 1.4±0.43 vs. 2.4±1.21, p<0.001); and global strain (-14.6±7.34% vs -20.9±3.24%, p<0.001) were lower in the obese group compared with the controls. These strain imaging parameters appear to be related to the severity of obesity and can contribute to increased BMI. Left ventricular mass was found to be correlated with a decrease in global LV strain. CONCLUSION: Our study showed that childhood obesity is associated with an alteration in the longitudinal LV function. Segmental analysis of the LV can provide subtle markers for the emergence of future obesity-related cardiac disease.
ABSTRACT
A direct effect of obesity on myocardial function has not been not well established. Our aim was to investigate the effect of body mass index (BMI) and homeostatic model assessment of insulin resistance (HOMA-IR) on left-ventricular (LV) myocardial function in normotensive overweight and obese children by tissue Doppler imaging (TDI). We calculated the mitral annular displacement index (DI) and myocardial performance index (MPI) using TDI indices of systolic and diastolic LV function. In this hospital-based, prospective cross-sectional study, we studied 60 obese (mean age 13.2 ± 2.0 years) and 50 normal children. Subjects were divided into three groups: group 1 (BMI < 25, n = 50, control), group 2 (BMI 25-29.9 kg/m(2), n = 30, overweight), and group 3 (BMI ≥ 30 kg/m(2), n = 30, morbidly obese). Standard echocardiography showed increased LV diameters and LV mass/index and preserved ejection fraction in obese children. By TDI, LV systolic and diastolic function showed that peak late myocardial velocity (Em = 15.4 ± 2 cm/s), peak early myocardial velocity (Am = 8.7 ± 1.3 cm/s), Em/Am ratio (1.8 ± 0.3), isovolumetric relaxation time (IVRT = 59.2 ± 8.2 ms), MPI (0.39 ± 0.03), and DI (25.5 ± 3.2 %) of the lateral mitral annulus in the obese subgroups were significantly different from those of control subjects (18.2 ± 1.2 cm/sn, 6.9 ± 0.6 cm/sn, 2.6 ± 0.2, 51.2 ± 9.6 ms, 0.34 ± 0.03, and 33.13 ± 5.0 %, respectively; p < 0.001). These structural and functional abnormalities were significantly related to BMI. There were positive correlations between HOMA-IR, septal MPI, and LV mass. DI and MPI data indicated impaired subclinical LV function in all grades of isolated obesity at a preclinical stage. Insulin resistance and BMI correlated significantly with indices of LV function.
