title: Relationship between cerebral blood flow and blood pressure in long-term heart transplant recipients.
abstract: Heart transplant recipients are at an increased risk for cerebral hemorrhage and ischemic stroke; yet, the exact mechanism for this derangement remains unclear. We hypothesized that alterations in cerebrovascular regulation is principally involved. To test this hypothesis, we studied cerebral pressure-flow dynamics in 8 clinically stable male heart transplant recipients (62±8 years of age and 9±7 years post transplant, mean±SD), 9 male age-matched controls (63±8 years), and 10 male donor controls (27±5 years). To increase blood pressure variability and improve assessment of the pressure-flow dynamics, subjects performed squat-stand maneuvers at 0.05 and 0.10 Hz. Beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal carbon dioxide were continuously measured during 5 minutes of seated rest and throughout the squat-stand maneuvers. Cardiac baroreceptor sensitivity gain and cerebral pressure-flow responses were assessed with linear transfer function analysis. Heart transplant recipients had reductions in R-R interval power and baroreceptor sensitivity low frequency gain (P<0.01) compared with both control groups; however, these changes were unrelated to transfer function metrics. Thus, in contrast to our hypothesis, the increased risk of cerebrovascular complication after heart transplantation does not seem to be related to alterations in cerebral pressure-flow dynamics. Future research is, therefore, warranted.
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.). jonathan.smirl@ubc.ca.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Smirl
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Haykowsky
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Michael D
authors.initials: MD
authors.lastname: Nelson
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Tzeng
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Katelyn R
authors.initials: KR
authors.lastname: Marsden
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Helen
authors.initials: H
authors.lastname: Jones
authors.affiliation: From the Department of Health and Social Development, Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, British Columbia, Canada (J.D.S., K.R.M., P.N.A.); Department of Physical Therapy, Faculty of Rehabilitation Medicine, University of Alberta and Mazankowki Alberta Heart Institute, Edmonton, Canada (M.J.H.); Cedars-Sinai Heart Institute, Los Angeles, CA (M.D.N.); Department of Surgery and Anaesthesia, Cardiovascular Systems Laboratory, Centre for Translational Physiology, University of Otago, Wellington, New Zealand (Y.-C.T.); and Department of Sport and Exercise Science, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK (H.J.).
authors.forename: Philip N
authors.initials: PN
authors.lastname: Ainslie
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D001955:British Columbia / Q000453:epidemiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005080:Exercise Test; D005500:Follow-Up Studies; D016027:Heart Transplantation; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011183:Postoperative Complications; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology / Q000209:etiology / Q000503:physiopathology*; D013997:Time Factors; D066027:Transplant Recipients; D017585:Ultrasonography, Doppler, Transcranial
keywords: autoregulation; blood pressure; cardiac transplantation; cerebrovascular circulation; transcranial Doppler ultrasonography