Cardiovascular autonomic modulation in essential hypertension. Effect of tilting.

Abstract

To better understand the role played by the autonomic nervous system in essential hypertension, we used autoregressive power spectrum analysis to study the noncasual oscillations in RR interval, blood pressure, and skin blood flow in 40 subjects with mild to moderate hypertension and in 25 age-matched control subjects at low frequency (index of sympathetic activity to the heart and the peripheral circulation) and high frequency, respiratory related (index of vagal tone to the heart). RR interval, respiration, noninvasive systolic blood pressure, and skin arteriolar blood flow were simultaneously and continuously recorded with subjects in the supine position and immediately after tilting. The low-frequency component was not significantly different in the two groups either at the cardiac level (control versus hypertensive subjects: 39

Does mental arithmetic before head up tilt have an effect on the orthostatic cardiovascular and hormonal responses?

“…Baroreceptor sensitivity decreased as well, suggesting an increased autonomic reactivity, which is in agreement with earlier reports [25].…”

“…Blood pressure changes reported here may not only reflect modulation of the autonomic system but vascular reactivity arising due to autonomic stimulation [25]. Moreover, spectral indices do not provide a real measure of nerve activities but only are markers of their overall interaction with target function [15].…”

Autonomic Blockade During Sinusoidal Baroreflex Activation Proves Sympathetic Modulation of Cerebral Blood Flow Velocity

“…Thus, our data confirmed that 0.2 Hz oscillations of BP are mechanically mediated oscillations, secondary to changes in respiration and cardiac output. 6,41,42 Moreover, our results showed that 0.2 Hz oscillations of CBFV also do not result from direct parasympathetic modulation, but are secondary to BP oscillations and their causation.…”

“…8,30 Instead, 0.2 Hz CBFV oscillations most likely arise from mechanical oscillations, secondary to BP oscillations and to respiration-induced changes in venous cardiac return and cardiac output. 6,41,42 As mentioned above, CA functions as a high-pass filter 26,27,43 that transfers BP oscillations at frequencies >0.1 Hz onto CBFV, 43 yielding secondary, mechanically induced CBFV oscillations at frequencies identical to the BP oscillations in the HF range. 6,41,42 As atropine had no effects on BP, CBFV, or on 0.2 Hz modulation of either signal, gain and phase shift between 0.2 Hz oscillations of BP and CBFV also remained unchanged.…”

Frequency domain analysis of heart rate variability in young obese adults with parental history of hypertension during isotonic exercise: A comparative study

“…[16,17] One study showed the evidence of poor vagal rebound after exercise in the group with H/O parental hypertension. [18] Probably, a similar mechanism of poor parasympathetic reactivation was operating in our study group too.…”