Obesity in Kids Affects Heart Shape, Functional Impairments

October 08, 2014

LEIPZIG, GERMANY — Changes in cardiac geometry and function resulting from obesity are observed as early as childhood, according to the results of a new study. Investigators observed thicker left ventricular (LV) walls and an increased LV mass, as well as impaired measures of systolic function, among the obese kids when compared with nonobese children[1].

The researchers observed no difference in ejection fractions between the obese and nonobese children, but the average LV strain, strain rate, and displacement, which are markers of LV longitudinal function assessed by 2D speckle-tracking echocardiography (2D-STE), were significantly impaired among the obese children.

In the study, published October 8, 2014 in the Journal of the American College of Cardiology, the researchers, led by Dr Norman Mangner (University of Leipzig, Germany), write that the relationship between obesity and cardiovascular risk is difficult to assess because obesity is associated with glucose intolerance, diabetes, high blood pressure, and elevated cholesterol levels.

"For this reason, children are likely to be the ideal candidates for providing insight into the myocardial changes related to obesity because they are suggested to be free of other cardiovascular risk factors in different echocardiographic studies," they write.

Thicker Ventricle Walls, Larger LV Mass

In the present study, they included 61 obese and 41 nonobese children aged nine to 16 years (average age 14 years). The subjects were matched in terms of age, sex, and height, but the obese children had significantly higher body-mass index (BMI 31 vs 19 kg/m2), larger waist circumferences, higher systolic blood pressure, and worse lipid and glucose metabolism parameters.

Compared with the nonobese group, the obese children had thicker LV walls, a 29% larger LV end-diastolic volume, and a 40% larger LV mass. Left atrial (LA) volume, LA volume index, right atrial area, and right ventricular diameter were also significantly larger in the obese children. The differences remained after adjustment for physical development and growth, although the indexed LV systolic and diastolic diameters were similar between the two groups.

"It is proven that LV dilation and LV hypertrophy, as well as LA enlargement, are associated with adverse cardiac events and worse prognosis," write Mangner and colleagues. "Furthermore, increased LA size is also a feature of impaired diastolic function of the left ventricle."

As noted, the researchers observed significant differences in longitudinal function by 2D-STE. In addition, they observed reduced average circumferential strain among the obese adolescents but no significant difference in the average strain rate. In a multivariate regression analysis, left ventricular longitudinal strain was independently associated with BMI as well as with HDL cholesterol, whereas circumferential strain was associated with BMI only.

Regarding mechanisms, Mangner et al say that the differences in blood pressure, even though they were within the normal range in the obese group, might be responsible for the changes in cardiac geometry. Previous studies have also suggested that insulin resistance might act as a mediator between obesity and congestive heart failure. In the present study, the obese children were already characterized by peripheral insulin resistance, they note.

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