PURPOSE: Obesity is independently associated with the risk of heart failure, but only recent studies with sophisticated echocardiographic techniques have demonstrated subclinical systolic abnormalities in obese subjects without clinical heart failure or depressed left ventricular ejection fraction. Such techniques provide important early markers of subclinical disease but are difficult to implement in large-scale studies or clinical practice. Impedance cardiography (ICG) represents an easily applicable, operator-independent technique to assess cardiac function. The purpose of this study is to determine whether abnormalities of systolic function can be identified in obese subjects with the use of ICG.
METHODS: We studied 310 non-institutionalized adults who were unmedicated and free of diabetes or heart failure as part of a population-based study. ICG was performed with the Bio-Z device (Cardiodynamics; San Diego, CA). Simple and multiple linear regression was used to identify associations between body mass index (BMI) and the systolic acceleration index (ACI) and velocity index (VI). To allow direct comparisons, all reported regression coefficients are standardized.
RESULTS: Highly significant univariate negative correlations between BMI and VI (R=−0.56; p<0.0001) and between BMI and ACI (R=−0.51; p<0.0001) were found. After adjusting for age, gender, HDL and LDL cholesterol, triglycerides, heart rate, systolic and diastolic blood pressure and stroke volume, BMI remained an independent negative predictor of both VI (β=−0.48; R2 increase=0.18; p<0.0001) and ACI (β=−0.43; R2 increase=0.14; p<0.0001). The correlation was also independent of systemic arterial compliance and baseline impedance. In these multivariate models BMI was the strongest predictor of both parameters. The adjusted partial correlation coefficients with BMI were –0.47 for ACI and −0.56 for VI (both p<0.0001). Interestingly, lower HDL levels also predicted lower AI and VI (independently of BMI), indicating that metabolic components associated with insulin resistance may play a role in these systolic abnormalities.
CONCLUSION: ICG readily identifies subclinical systolic abnormalities associated with obesity.
CLINICAL IMPLICATIONS: ICG provides an easily applicable tool for early detection of subclinical cardiac functional changes associated with obesity.
DISCLOSURE: Julio Chirinos, None.