Sympathetic predominance in hypertension is associated with deleterious effects on target organs and predicts the development of cardiovascular complications. The effects of antihypertensive agents on cardiovascular autonomic modulation remain controversial.Design and Method:
53 patients with essential hypertension and 39 healthy subjects were recruited into the study. Among the patients with hypertension, 22 patients were unmedicated, 19 patients were being treated with an angiotensin II receptor antagonist (ARB), and 12 patients were being treated with a calcium channel blocker (CCB). Participants underwent polysomnography and noninvasive continuous arterial blood pressure recording simultaneously during nap sleep. The results were used for heart rate variability (HRV), and spontaneous baroreflex sensitivity (BRS) analysis. Spectral analysis of the HRV was performed to assess the cardiac parasympathetic modulation (high-frequency power, HF) and cardiac sympathetic modulation (normalized low-frequency power, LF% and LF/HF ratio). Spontaneous BRS was estimated from (1) the magnitudes of arterial pressure and R-R interval transfer function across both the high frequency (BrrHF) and low frequency (BrrLF) ranges and (2) the slopes of the linear regression of the mean arterial pressure and R-R intervals pairs that both ascended (BrrA) and descended (BrrD) successively.Results:
While awake, the unmedicated hypertensive subjects showed lower parasympathetic activity (HF) and higher sympathetic activities (LF/HF and LF%) than the controls. In contrast, the ARB group showed only lower HF power than the controls, but had similar sympathetic (LF/HF or LF%) activities. There was no significant difference in HF, LF/HF or LF% between the CCB and control groups. All hypertensive patients, with or without antihypertensive agents, showed lower BRS indices, BrrLF, BrrHF, BrrA, and BrrD, based on the arterial pressure variability analysis, than the controls during waking.Conclusions:
Among hypertensive patients treated with either ARB or CCB, any increases in cardiac sympathetic activities were normalized; however the reduction in BRS associated with hypertension was not affected.