Background: Hypertension is known to increase the limits of static cerebral autoregulation (CA) but its effects on other aspects of CA such as efficiency and latency are unknown. In this study we test the hypothesis that dynamic cerebral autoregulation and the efficiency of static cerebral autoregulation are impaired by untreated hypertension.
Methods: Cerebral blood flow velocity was recorded using transcranial Doppler ultrasound, along with noninvasive beat-to-beat blood pressure (BP), electrocardiogram, and transcutaneous carbon dioxide levels, with subjects at rest and during isometric hand grip, thigh cuff, and the Valsalva maneuver. Static and dynamic CA indices were calculated.
Results: No significant difference was seen in static or dynamic CA indices between normotensive and hypertensive groups for any pressor or depressor stimulus. Spearman's rank correlation showed no relation between static or dynamic CA indices and systemic BP levels for all maneuvers, but a significant relationship between age and static CA index, determined using isometric handgrip (P =.002), was found.
Conclusions: In middle-aged and older people, sustained untreated hypertension does not alter dynamic CA or the efficiency of static CA within the BP limits studied.