PARASYMPATHETIC WITHDRAWAL PRECEDES SPONTANEOUS BLOOD-PRESSURE ELEVATIONS IN WOMEN WITH PRIMARY HYPERTENSION

Exaggerated sympathetic activity is widely accepted as one of the fund amental mechanisms leading to primary hypertension and being responsib le for frequent episodes of blood pressure elevation in hypertensive p atients. Some data suggest also that basal parasympathetic tone in thi s entity is lowered. However, the effects of autonomic nervous activit y on heart rate variability during spontaneous blood pressure elevatio ns have not been yet evaluated. That is why we present the preliminary results of 24-hour electrocardiogram and blood pressure monitoring in 13 women with mild primary hypertension and with 25 episodes of blood pressure elevations. Time- and frequency-domain measurements of heart rate variability found during the 24- and 10-hour daily periods were compared with those obtained during four 5-min records: 25-20, 15-10 m in and immediately before, as well as immediately after the recording of blood pressure elevation. Significant decrease in parameters repres enting vagal tone was found during 5-min periods not only immediately preceding or following blood pressure elevations, but also 10 and 20 m in before these episodes. Moreover, low-frequency component of heart r ate variability was significantly lowered 10 min before and immediatel y after the recording of blood pressure elevation. These results sugge st that among various pathogenetic mechanisms of spontaneous blood pre ssure elevations in women with primary hypertension, sudden withdrawal of parasympathetic tone should be taken into account.