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Updated: Apr 23, 2026
A Pre-Clinical Porcine Model of Orthotopic Heart Transplantation
Published on: April 27, 2019
Relationship between cerebral blood flow and blood pressure in long-term heart transplant recipients
Jonathan D Smirl1, Mark J Haykowsky2, Michael D Nelson2
1From 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.
Insights
Heart transplant recipients face higher stroke risks, but this study found no link to altered cerebral pressure-flow dynamics. Further research is needed to understand these cerebrovascular complications.
Area of Science:
- Cardiovascular Science
- Neurology
- Transplantation Medicine
Background:
- Heart transplant recipients have an elevated risk of cerebrovascular events like stroke.
- The underlying mechanisms contributing to this increased risk remain poorly understood.
Purpose of the Study:
- To investigate whether altered cerebrovascular regulation, specifically pressure-flow dynamics, contributes to the increased risk of stroke in heart transplant recipients.
- To assess cardiac baroreceptor sensitivity and cerebral pressure-flow responses during dynamic maneuvers.
Main Methods:
- Studied 8 male heart transplant recipients, 9 age-matched male controls, and 10 male donor controls.
- Measured beat-to-beat blood pressure, middle cerebral artery velocity, and end-tidal carbon dioxide during rest and squat-stand maneuvers (0.05 and 0.10 Hz).
- Utilized linear transfer function analysis to assess cardiac baroreceptor sensitivity and cerebral pressure-flow dynamics.
Main Results:
- Heart transplant recipients exhibited reduced R-R interval power and baroreceptor sensitivity low frequency gain compared to controls (P<0.01).
- These autonomic function changes were not correlated with cerebral pressure-flow transfer function metrics.
- The study did not find evidence of altered cerebral pressure-flow dynamics in heart transplant recipients.
Conclusions:
- The increased risk of cerebrovascular complications after heart transplantation does not appear to be primarily related to alterations in cerebral pressure-flow dynamics.
- Findings suggest that other mechanisms may be responsible for the heightened risk of stroke in this population.
- Further investigation is warranted to elucidate the exact causes of cerebrovascular derangements post-heart transplantation.
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.
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