The potent role of increased sympathetic tone in pathogenesis of essentialhypertension with neurovascular compression

Objective: To study the role of increased sympathetic tone in pathogenesis of hypertension in patients with essential hypertension with neurovascular compression. Methods: Twenty-three patients with essential hypertension, 13 patients wit h secondary hypertension, and 46 normotensive subjects were investigated. N eurovascular compression was evaluated by MRT. The power spectral component s of heart rate variability as indices of autonomic nerve tone were determi ned to investigate the possibility that sympathetic tone mediates the neuro vascular compression-induced increase in blood pressure. Results: Neurovascular compression of the rostral ventrolateral medulla (RV LM) was observed in 70% of essential hypertension group, none of secondary hyperension group and 16% of normotensive group IP < 0.001). The age-adjust ed low-frequency power spectral density (A-PSD) (0.04 to 0.15 Hz), which is an index of sympathetic tone, was significantly higher in patients with es sential hypertension (139.5 +/- 6.7%) with neurovascular compression than i n essential hypertension patients without neurovascular compression (92.2 /- 6.8%), normotensive subjects with (102.8 +/- 13.0%) and without neurovas cular compression (100.1 +/- 4.1%), and patients with secondary hypertensio n (95.7 +/- 10.2%) (P < 0.001). There was no significant difference in the high-frequency A-PSD (0.15 to 0.40 Hz), which is an index of vagal tone, am ong groups. Conclusions: Neurovascular compression was not always associated with an in crease in sympathetic nerve tone. Hypertension was present in subjects with neurovascular compression, who had increased sympathetic tone but not in t hose with normal sympathetic tone. An increase in sympathetic tone may medi ate the neurovascular compression-induced increase in blood pressure.