Evidence for Abnormalities in Parasympathetic Nerve-Mediated Reflexes in Borderline Hypertension.

This study was designed to elucidate the abnormalities in both the parasympathetic and sympathetic nervous systems in borderline hypertension. Utilizing the cold pressor test (CPT) for evaluation of the sympathetic nervous system and R-R interval variation for the assessment of the parasympathetic nervous system, fifteen male patients (37±4 y.o.) with borderline hypertension (mean arterial pressure=111±2mmHg) and age-matched normotensive controls participated in this study. The cold face test (CFT), which is able to evaluate the trigeminal-vagal-cardiac and trigeminal-sympathetic-peripheral vasculature pathways, was also employed to evaluate the balance between these two divisions of the autonomic nervous system. The coefficient of variation (CV) of R-R interval variation in the borderline hypertensives was significantly smaller than that in the controls (3.9±0.3vs. 6.3±0.4%, P<0.01). The CPT produced a significant elevation of blood pressure in both groups, but there were no significant differences between the two groups. The CFT induced bradycardia (P<0.01) in the controls, while hypertensive subjects were characterized by an increase in systolic blood pressure (P<0.01) without significant changes in heart rate. Epinephrine was significantly decreased by the CFT only in the controls. There was a positive correlation between CV of R-R interval and decrease in heart rate by the CFT (r=0.60, P<0.0005). These results suggest that even with a specifically vagal reflex, patients with borderline hypertension have decreased parasympathetic tone and that the CFT may be useful in the assessment of the balance between the sympathetic and parasympathetic nervous systems over the regulation of the effector organs. (Hypertens Res 1993; 16: 185- 190)