Relationship between central sympathetic activity and stages of human hypertension

The magnitude of sympathetic hyperactivity in essential hypertension (EHT) varies with its severity and complications. There are no data on sympathetic nerve activity in borderline (BHT) or white-coat hypertension (WHT) relative to the various stages of EHT, despite suggestions that both lead to established EHT and organ damage through sympathetic mechanisms. We planned to determine the magnitude of sympathetic nerve activity in patients with BHT and WHT in relation to normality and various stages of sustained EHT. We examined 90 untreated subjects comprising matched groups with BHT ( n = 13), WHT ( n = 12), Sixth Report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure EHT stage 1 (EHT-1 n = 12), EHT stages 2 and 3 (EHT-2/3 n = 14), high–normal pressure (HN n = 14), and normal pressure (NT n = 13), as well as a group with EHT complicated by left ventricular hypertrophy (EHT+LVH n = 12). We quantified muscle sympathetic nerve activity as the mean frequency of multiunit discharge (MSNA) and that of single-units (s-MSNA). We found a greater (at least P < .01) mean central sympathetic frequency in BHT (75 ± 5.8 impulses/100 beats), EHT-1 (76 ± 4.0 impulses/100 beats), and EHT+LVH (79 ± 4.3 impulses/100 beats) than in EHT-2/3 (57 ± 3.1 impulses/100 beats), WHT (52 ± 3.6 impulses/100 beats), HN (42 ± 3.9 impulses/100 beats), and NT (33 ± 3.6 impulses/100 beats). BHT hyperactivity was closer to that of EHT, whereas WHT was closer to NT. Central sympathetic activity was greatest in BHT, early stage, and complicated EHT, and as such is likely to play an integral role in the development of hypertension and its complications. Sympathetic hyperactivity occurs in WHT, but to a lesser extent than in BHT.