Autonomic control of the cerebral circulation during normal and impaired peripheral circulatory control.
OBJECTIVE
To determine whether oscillations in the cerebrovascular circulation undergo autonomic modulation in the same way as cardiovascular oscillations.


METHODS
Cardiovascular and cerebrovascular oscillations were monitored at rest and during sympathetic stimulation (head up tilt). The association with and transmission of the oscillations in the sympathetic (low frequency, LF) and respiratory (high frequency, HF) bands was assessed.


METHODS
13 healthy volunteers, 10 subjects with vasovagal syncope, and 12 patients with complicated non-insulin dependent diabetes mellitus.


METHODS
Power spectrum analysis of cerebral blood flow velocity, arterial blood pressure, and heart rate. Coherence analysis was used to study the association between each pair of oscillations. Phase analysis showed the delay of the oscillations in the cardiovascular signals with respect to the cerebrovascular signals.


RESULTS
The power in the sympathetic (LF) components in all the oscillations increased during head up tilt (p < 0.01) in the controls and in the subjects with vasovagal syncope, but not in patients with diabetes. Significant coherence (> 0.5) in the LF band was present between cerebrovascular and cardiovascular oscillations in most of the controls and in subjects with vasovagal syncope, but not in the diabetic patients (< 50% of the patients). In the LF band, cerebrovascular oscillations preceded the cardiovascular oscillations (p < 0.05) at rest in all groups: the phase shifts were reduced (p < 0.05) during head up tilt for all cardiovascular signals in healthy and syncopal subjects, but only for heart rate in diabetic patients.


CONCLUSIONS
The cerebrovascular resistance vessels are subject to autonomic modulation; low frequency oscillations in cerebral blood flow velocity precede the resulting fluctuations in other cardiovascular signals. Autonomic neuropathy and microvascular stiffness in diabetic patients reduces this modulation.
Cencetti
S
S
Medicina Interna 1, S Maria Nuova Hospital, Florence, Italy.
Lagi
A
A
Cipriani
M
M
Fattorini
L
L
Bandinelli
G
G
Bernardi
L
L
D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001683:Biological Clocks / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003929:Diabetic Neuropathies / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D011187:Posture / Q000502:physiology; D012815:Signal Processing, Computer-Assisted; D019462:Syncope, Vasovagal / Q000503:physiopathology*; D018667:Tilt-Table Test