title: Hemodynamic variability and cerebrovascular control after transient cerebral ischemia.
abstract: We investigated if hemodynamic variability, cerebral blood flow (CBF) regulation, and their interrelationships differ between patients with transient ischemic attack (TIA) and controls. We recorded blood pressure (BP) and bilateral middle cerebral artery flow velocity (MCAv) in a cohort of TIA patients (n = 17), and age-matched controls (n = 15). Spontaneous fluctuations in BP and MCAv were characterized by spectral power analysis, and CBF regulation was assessed by wavelet phase synchronization analysis in the very low- (0.02-0.07 Hz), low- (0.07-0.20 Hz), and high-frequency (0.20-0.40 Hz) ranges. Furthermore, cerebrovascular CO2 reactivity was assessed as a second metric of CBF regulation by inducing hypercapnia with 8% CO2 inhalation followed by hyperventilation driven hypocapnia. We found that TIA was associated with higher BP power (group effect, P < 0.05), but not MCAv power (P = 0.11). CBF regulation (assessed by wavelet phase synchronization and CO2 reactivity) was intact in patients (all P ≥ 0.075) across both hemispheres (all P ≥ 0.51). Pooled data (controls and affected hemisphere of patients) showed that BP and MCAv power were positively correlated at all frequency ranges (R(2) = 0.20-0.80, all P < 0.01). Furthermore, LF phase synchronization index was a significant determinant of MCAv power (P < 0.05), while VLF and HF phase synchronization index, and TIA were not (all P ≥ 0.50). These results indicate that CBF stability and control is maintained in TIA patients, but BPV is markedly elevated. BPV attenuation may be an important therapeutic strategy for enhancing secondary stroke prevention in patients who suffer a TIA.
authors.affiliation: Centre for Translational Physiology, University of Otago, Wellington, New Zealand Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.
authors.forename: Philip D
authors.initials: PD
authors.lastname: Allan
authors.affiliation: Department of Sport and Exercise, University of Winchester, Winchester, UK.
authors.forename: James
authors.initials: J
authors.lastname: Faulkner
authors.affiliation: Centre for Translational Physiology, University of Otago, Wellington, New Zealand Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand.
authors.forename: Terrence
authors.initials: T
authors.lastname: O'Donnell
authors.affiliation: Department of Neurology, Wellington Hospital, Wellington, New Zealand.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Lanford
authors.affiliation: Department of Neurology, Wellington Hospital, Wellington, New Zealand.
authors.forename: Lai-Kin
authors.initials: LK
authors.lastname: Wong
authors.affiliation: Centre for Translational Physiology, University of Otago, Wellington, New Zealand School of Engineering and Computer Science, Victoria University of Wellington, Wellington, New Zealand.
authors.forename: Saqib
authors.initials: S
authors.lastname: Saleem
authors.affiliation: School of Sport and Exercise, Massey University, Wellington, New Zealand.
authors.forename: Brandon
authors.initials: B
authors.lastname: Woolley
authors.affiliation: Faculty of Health Science, University of Southampton, Southampton, UK.
authors.forename: Danielle
authors.initials: D
authors.lastname: Lambrick
authors.affiliation: School of Sport and Exercise, Massey University, Wellington, New Zealand.
authors.forename: Lee
authors.initials: L
authors.lastname: Stoner
authors.affiliation: Centre for Translational Physiology, University of Otago, Wellington, New Zealand Department of Surgery and Anaesthesia, University of Otago, Wellington, New Zealand shieak.tzeng@otago.ac.nz.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Tzeng
keywords: Blood pressure; cerebral blood flow; cerebral hemodynamics; transient ischemic attack