RELATIONSHIP BETWEEN SYMPATHETIC TONE AND PARASYMPATHETIC NERVOUS ACTIVITY IN ESSENTIAL-HYPERTENSION PATIENTS

The relationship between changes in sympathetic and parasympathetic nervous activity induced by postural change was investigated in patients with essential hypertension using the coefficient of variation of RR intervals on ECG (CV) as the index of parasympathetic activity. Mean arterial pressure (MAP), heart rate (HR), plasma noradrenaline concentration (pNA) and CV were measured in a supine position at rest and 20 min after an upright tilt in 10 normotensive subjects (NT) and 7 essential hypertension patients (EHT). After altering the position, HR and pNA significantly increased without changes in MAP in both groups, whereas CV decreased significantly in NT but not in EHT. A significantly negative correlation between percent changes in CV (%Delta CV) and pNA (%Delta pNA) was observed in NT but not in EHT. However, there was no significant relationship between %Delta CV and %Delta MAP nor %Delta HR in either group. Parasympathetic nervous system appears to interact with sympathetic tone but to be impaired in EHT.