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Exaggerated sympathetic activity is widely accepted as one of the fundamental mechanisms leading to primary hypertension and being responsible for frequent episodes of blood pressure elevation in hypertensive patients. Some data suggest also that basal parasympathetic tone in this entity is lowered. However, the effects of autonomic nervous activity on heart rate variability during spontaneous blood pressure elevations 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 min and immediately before, as well as immediately after the recording of blood pressure elevation. Significant decrease in parameters representing vagal tone was found during 5-min periods not only immediately preceding or following blood pressure elevations, but also 10 and 20 min before these episodes. Moreover, low-frequency component of heart rate variability was significantly lowered 10 min before and immediately after the recording of blood pressure elevation. These results suggest that among various pathogenetic mechanisms of spontaneous blood pressure elevations in women with primary hypertension, sudden withdrawal of parasympathetic tone should be taken into account.

In phaeochromocytoma, sudden hypertensive or arrhythmic episodes are believed to be associated with excessive free catecholamine excretion. However, lack of correlation between blood pressure (BP) and plasma catecholamine levels has been reported. Therefore an attempt was made to assess the sympathovagal balance before and during episodes of BP elevation or complex cardiac arrhythmias in this disease. Ten patients with phaeochromocytoma and 10 matched controls with essential hypertension underwent simultaneous 24 h Holter ECG and BP monitoring. BP elevation was diagnosed when the BP exceeded the mean 24 h values by 40 mm Hg systolic or 30 mm Hg diastolic, respectively. Heart rate variability (HRV) was measured for 5 min periods 1 h before, 15 min before and during 13 episodes of BP elevation in phaeochromocytoma and 13 episodes in the control group, as well as at 1 h, 15 min and immediately before five arrhythmic events in phaeochromocytoma. In phaeochromocytoma, vagal activity measured 1 h before BP elevation was markedly higher than in control hypertensives. However, in both groups at 15 min before and during the hypertensive events, the vagal tone decreased significantly. In contrast, just before the arrhythmic events HRV remained unaltered with a slight insignificant increase in sympathetic activity. We conclude that in phaeochromocytoma, pronounced BP elevations during daily activities are preceded by a parasympathetic withdrawal, similar to the findings in essential hypertension. Such a sequence does not seem to precede sudden complex arrhythmic events in phaeochromocytoma.

We evaluated the effect of captopril treatment on left ventricular mass (LVM) and function in sustained mild-to-moderate primary hypertension. In 16 men aged 34.5 +/- 6.4 yrs. M-mode echo and pulsed wave Doppler recordings were obtained prior to and after 2 months captopril treatment (50-150 mg daily). No significant changes in heart rate, systolic blood pressure, ejection fraction, fractional shortening, cardiac output, LVM and Doppler-derived indices of mitral inflow were observed. Diastolic blood pressure measured during examination fell from 102.2 +/- 13.3 to 90.3 +/- 9 mmHg (p less than 0.026). No consistent correlations between catecholamines and indexes of left ventricular function were found. Two-month captopril therapy in mild-to-moderate hypertension results in diastolic blood pressure lowering with no effect on LVM or left ventricular function.