The Coefficient of Variation of RR Intervals (CV_RR) on Electrocardiogram in Patients with Essential Hypertension with Reference to Aging, Hemodynamics and Sympatho-Adrenomedullary Function

Abstract

To evaluate the significance of parasympathetic nerve activity in essential hypertension, we measured the coefficients of variation of RR intervals (CV_RR) on electrocardiogram and examined the relationships between CV_RR and aging, hemodynamics and sympathoadrenomedullary function in normotensive subjects (NT) and in patients with essential hypertension (EHT). Mean arterial pressure (MAP), heart rate (HR), plasma noradrenaline concentration (pNA), plasma adrenaline concentration (pAd) and CV_RR resting in a supine position were simultaneously measured in 37 NT (33.8±2.0 years) and 47 mild-to-moderate EHT (51.3±1.5 years). In both NT and EHT, significantly negative correlations between CV_RR and age (NT: r=-0.54, p<0.001, EHT: r=-0.41, p<0.005) were observed, however, CV_RR correlated with neither MAP, HR nor pAd. CV_RR tended to correlate negatively with pNA (r=-0.27, p<0.1) in NT, unlike in EHT. The mean value of CV_RR in EHT (n=10, age: 38.3±1.6 years, CV_RR: 3.61±0.37%) was significantly (p<0.005) lower than in age-matched NT (n=10, age: 38.3±2.5 years, CV_RR: 5.76±0.45%). These results indicate that the parasympathetic tone suggested by CV_RR may be related to aging and sympathetic nerve activity, and that parasympathetic function might be impaired in EHT.