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One third of adolescents are obese in the United States. Half of them have insulin resistance (IR). Animal and human adult studies suggest that IR is associated with alterations in myocardial substrate metabolism and efficiency that lead to cardiac dysfunction. We hypothesize that in obese adolescents (body mass index, BMI > 95th percentile for age and gender), IR is associated with cardiac dysfunction that is independent of conventional cardiovascular risk factors.
Forty-one obese adolescents (aged 14.7±1.9 years, BMI 33.7±7.9 kg/m2) were compared with 14 healthy age-, Tanner stage-, and gender matched (aged 15.3±1.4 years, BMI 19.9±1.6 kg/m2) subjects in a cross-sectional study for metabolic profiles and cardiovascular risk factors. Cardiac function and structure were evaluated by standard and speckle tracking echocardiography. Left ventricular global longitudinal strain (GLS) and strain rate (GSR) were measured. Groups were compared by t-tests, Wilcoxon test, linear and multivariate regression.
The obese subjects had significantly elevated insulin (U/L), IR by homeostasis model assessment (HOMA1) and LDL (mg/dl) in comparison with the controls (18.3 vs. 8.3, p=0.008; 3.9 vs.1.84, p=0.01; and 132 vs.69, p<0.0001). Blood pressure was similar. Peak GLS (−%), systolic and early diastolic GSR (−%/s) were significantly lower in the obese adolescents compared with the lean controls (−15.97 vs. −18.16, p=0.02; −0.93 vs. −1.03, p=0.03; and 1.58 vs. 1.34, p=0.02) and correlated with fasting insulin (r = −0.38,-0.34, −0.44), HOMA1 (r = −0.34, −0.31,-0.41) and BMI (−0.47, −0.40, −0.56). There was no correlation with lipids and blood pressure. By multivariate analysis, BMI was significantly associated with peak GLS and GSR. BMI was strongly correlated with insulin (r=0.63) and HOMA1(r=0.60).
Obese adolescents have abnormal myocardial deformation properties that are associated with the severity of obesity and IR, independently from conventional cardiovascular risk factors. This represents an early onset of impaired cardiac function in obese adolescents that may foreshadow a concerning trend towards pediatric onset of obesity cardiomyopathy.
Poster Sessions, Expo North
Monday, March 11, 2013, 9:45 a.m.-10:30 a.m.
Session Title: Imaging: Cardiac Abnormalities in Non-Cardiac Disorders, Hand Held Echocardiography, Cardiac Masses
Abstract Category: 18. Imaging: Echo
Presentation Number: 1311-326
- 2013 American College of Cardiology Foundation