|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1997 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1996 : ¥1,200,000 (Direct Cost : ¥1,200,000)
There are physiological and anatomical reasons to suspect that neurovascular compression of the rostral ventrolateral medulla (RVLM) may cause essential hypertension. Clinical studies using magnetic resonance tomography (MRT) have found that neurovascular compression of the RVLM is related to essential hypertension. However, the mechanism of a neurovascular compression-induced increase in blood pressure has not been investigated in a clinical study.
Methods We investigated the neurovascular compression-induced increase in 23 patients with essential hypertension (EHT), 13 patients with secondary hypertension (SHT), and 46 normotensive subjects (NT). Neurovascular compression was evaluated by MRT.We determined the power spectral components of heart rate variability as indices of autonomic nerve tone to investigate the possibility that sympathetic tone mediates the neurovascular compression-induced increase in blood pressure. The power spectral density was calculated by fast Fourier transf
orm in a series of 256 consecutive and stationary cardiac interval.
Findings Neurovascular compression of the RVLM was observed in 70% of EHT,none of SHT and 16% of NT (p<0.001). The age-adjusted low-frequency power spectral density (A-PSD), which is an index of sympathetic tone, was significantly higher in patients with EHT (139.5%) with neurovascular compression than in EHT without neurovascular compression (92.2%), NT with (102.8%) and without neurovascular compression (100.1%), and patients with SHT (95.7%) (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, among groups.
Interpretation Neurovascular compression, assessed by MRT,was not always associated with an increase in sympathetic nerve tone. Hypertension was present in subjects with neurovascular compression, who had increased sympathetic tone but not in those with normal sympathetic tone. The present findings confirm that essential hypertension is associated with neurovascular compression and suggest that an increase in sympathetic tone may mediate the neurovascular compression-induced increase in blood pressure. Less