Autonomic dysfunction affects dynamic cerebral autoregulation during Valsalva maneuver: comparison between healthy and autonomic dysfunction subjects

Abstract

The role of autonomic nervous system (ANS) in adapting cerebral blood flow (CBF) to arterial blood pressure (ABP) fluctuations [cerebral autoregulation (CA)] is still controversial. We aimed to study the repercussion of autonomic failure (AF) on dynamic CA during the Valsalva maneuver (VM). Eight AF subjects with familial amyloidotic polineuropahty (FAP) were compared with eight healthy controls. ABP and CBF velocity (CBFV) were measured continuously with Finapres and transcranial Doppler, respectively. Cerebrovascular response was evaluated by cerebrovascular resistance index (CVRi), critical closing pressure (CrCP), and resistance-area product (RAP) changes. Dynamic CA was derived from continuous estimates of autoregulatory index (ARI) [ARI(t)]. During phase II of VM, FAP subjects showed a more pronounced decrease in normalized CBFV (78 ± 19 and 111 ± 16%; P = 0.002), ABP (78 ± 19 and 124 ± 12%; P = 0.0003), and RAP (67 ± 17 and 89 ± 17%; P = 0.019) compared with controls. CrCP and CVRi increased similarly in both groups during strain. ARI(t) showed a biphasic variation in controls with initial increase followed by a decrease during phase II but in FAP this response was blunted (5.4 ± 3.0 and 2.0 ± 2.9; P = 0.033). Our data suggest that dynamic cerebral autoregulatory response is a time-varying phenomena during VM and that it is disturbed by autonomic dysfunction. This study also emphasizes the fact that RAP + CrCP model allowed additional insights into understanding of cerebral hemodynamics, showing a higher vasodilatory response expressed by RAP in AF and an equal CrCP response in both groups during the increased intracranial and intrathoracic pressure, while classical CVRi paradoxically suggests a cerebral vasoconstriction.

Hemorrhagic transformation and cerebral edema in acute ischemic stroke: Link to cerebral autoregulation

“…Dynamic cerebral autoregulation using transfer function analysis has been widely studied in cerebrovascular disease [9–11,15,16,23–30]. Lower phase shift, reflecting less effective autoregulation, has been demonstrated in poorly compensated carotid or MCA stenosis [27,29, 30] or vasospasm after subarachnoid hemorrhage [27,28] as well as in ischemic stroke [15,16].…”

“…Dynamic cerebral autoregulation (CA) can be rapidly and noninvasively assessed at the bedside by transfer function analysis (TFA) between spontaneous oscillations in blood pressure and cerebral blood flow velocity [9–14]. There is an overall agreement that dynamic CA is impaired in acute IS [15,16] but its relationship with HT or CE is not known.…”

The effect of an acute increase in central blood volume on the response of cerebral blood flow to acute hypotension

“…Previous investigations (3,6,(35)(36)(37) reported that dynamic CA is unlikely to be constant and is altered by a change in cerebral vascular condition. For example, hypercapnia-induced cerebral vasodilation attenuates dynamic CA, while hypocapnia-induced cerebral vasoconstriction enhances dynamic CA (1).…”

Comparison of cerebrovascular reactivity tests: a pilot human study

“…Frequently volunteers blinked their eyes, thereby causing artifacts in the REG signal. Inconsequential changes observed during Valsalva maneuver may have been caused by autonomic dysfunction, previously described by Castro [18].…”

“…During turning of the titling table, large artifacts in the signal occurred at the beginning and end of the tests. This multiphase reaction may reflect orthostatic intolerance, caused by complex interactions of central and peripheral cardiovascular control [18].…”