Racial differences in the association between heart rate variability and left ventricular mass.

What is the central question of this study? Decreased heart rate variability (HRV) is associated with increased cardiovascular disease (CVD) risk, including greater left ventricular mass (LVM). Despite their enhanced CVD risk profile, African Americans have been shown to exhibit higher HRV, relative to Whites; however, it is unclear whether this pattern extends to the association between HRV and LVM. What is the main finding and its importance? Using ECG and echocardiographic data, HRV was positively associated with LVM in a non-clinical sample of African Americans. These findings suggest that current assumptions regarding the meaning of higher HRV might not be universal, which might have implications for HRV as a risk marker among African Americans. Increased left ventricular mass (LVM) is an early precursor of target organ damage attributable to hypertension. Diminished parasympathetic cardiac control has been linked to both hypertension onset and left ventricular impairment; however, emerging evidence suggests that this pattern might be different in African Americans. The present study sought to determine whether race impacts the relationship between parasympathetic cardiac control and LVM. The LVM was assessed via echocardiography in a sample (n = 148) of African American and White adults (mean age 33.20 ± 5.71 years) with normal or mildly elevated blood pressure. Parasympathetic cardiac control was assessed by a measure of high-frequency heart rate variability (HF-HRV) determined from ECG recordings during 5 min of rest. In regression analysis, greater HF-HRV was associated with greater LVM among African Americans (P = 0.002) but was not related to LVM in Whites (P = 0.919). These are the first data to demonstrate that race moderates the relationship between HRV and LVM and further suggest that race might be an important factor in the association between parasympathetic cardiac control and other cardiovascular disease risk factors.