[The coefficient of variation of RR intervals (CVRR) on electrocardiogram in patients with essential hypertension with reference to aging, hemodynamics and sympatho-adrenomedullary function].

To evaluate the significance of parasympathetic nerve activity in essential hypertension, we measured the coefficients of variation of RR intervals (CVRR) on electrocardiogram and examined the relationships between CVRR and aging, hemodynamics and sympatho-adrenomedullary 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 CVRR 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 CVRR and age (NT: r = -0.54, p less than 0.001, EHT: r = -0.41, p less than 0.005) were observed, however, CVRR correlated with neither MAP, HR nor pAd. CVRR tended to correlate negatively with pNA (r = -0.27, p less than 0.1) in NT, unlike in EHT. The mean value of CVRR in EHT (n = 10, age: 38.3 +/- 1.6 years, CVRR: 3.61 +/- 0.37%) was significantly (p less than 0.005) lower than in age-matched NT (n = 10, age: 38.3 +/- 2.5 years, CVRR: 5.76 +/- 0.45%). These results indicate that the parasympathetic tone suggested by CVRR may be related to aging and sympathetic nerve activity, and that parasympathetic function might be impaired in EHT.