REDUCED PARASYMPATHETIC CARDIAC CONTROL IN PATIENTS WITH HYPERTENSIONAT REST AND UNDER MENTAL STRESS

The neurogenic component in the pathogenesis of essential hypertension has predominantly been analyzed with regard to the sympathetic part o f the autonomous nervous system; the parasympathetic branch has largel y been neglected. We investigated whether 54 normotensive (mean casual blood pressure [cBP]: 125 +/-: 6/82 +/- 4 mm Hg), 41 borderline hyper tensive (cBP: 134 +/- 8/90 +/- 5 mm Hg), and 34 hypertensive men (cBP: 152 +/- 13/101 +/- 5 mm Hg) without secondary target organ damage dif fered in parasympathetic cardiac control. Parasympathetic cardiac cont rol was assessed via the amount of fast fluctuations (0.15 to 0.40 Hz; vagus band) and by the amount of respiratory-linked fluctuations (mea n respiratory frequency +/- 0.03 Hz) in the power spectra of continuou sly registered interbeat intervals under the following conditions: mea n of three rest phases with 10, 5, and 5 minutes' duration (REST); mea n of two modes of a reaction time task with 10 and 5 minutes' duration (RTT); mean of 5 minutes' mental arithmetic plus noise (MA). Analysis of variance (ANOVA) shows that spectral energy in the so-called vagus band reveals the most prominent differences between blood pressure gr oups under all conditions: REST = normotensive, 2.70 +/- 0.31; borderl ine hypertensive, 2.55 +/- 0.33; and hypertensive, 2.43 +/- 0.43 (F[2. 126] = 6.19; p< 0.01). RTT = normotensive, 2.41 +/- 0.35; borderline h ypertensive, 2.19 +/- 0.33; and hypertensive, 2.17 +/- 0.46 (F[2.126] = 6.04; P < 0.01); MA = normotensive, 2.69 +/- 0.34; borderline hypert ensive, 2.52 +/-: 0.33; and hypertensive, 2.38 +/- 0.46 (F[2.126] = 7. 04; p< 0.01). The ratio between the midfrequency band around 0.10 Hz a nd the vagus band, tentatively representing sympathovagal balance, is increased in both nonnormotensive groups, indicating a relative prepon derance of sympathetic efferents. The results demonstrate that a reduc tion in parasympathetic cardiac control significantly contributes to a disturbance in Sympathetic and parasympathetic cardiovascular control in hypertension.