Proceedings of The Physiological Society
University of Oxford (2011) Proc Physiol Soc 23, C21
Cerebral blood flow in heart transplant recipients: rest and during exercise
J. Smirl1, M. J. Haykowsky2, K. R. Marsden1, H. Jones3, M. D. Nelson2, P. N. Ainslie2, L. A. Altamirano-Diaz1
1. Department of Human Kinetics, UBC Okanagan, Kelowna, British Columbia, Canada. 2. Department of Physical Therapy, University of Alberta, Edmonton, British Columbia, Canada. 3. School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
Background and hypotheses: Pathological impairments in cardiac output may impact on cerebral blood flow velocity (CBFv). Prior studies that have measured CBF in heart transplant recipients (HTR) has reported increases 25-53% 1-6 months post-transplant1,2,3. It is unknown if CBF is altered over the longer-term (i.e. years) following transplant or during progressive exercise stress. The aim of this study was to examine the influence of long-term heart transplantation on the regulation of CBFv at rest and during progressive exercise. To address this aim, we used stable HTR who have a reported inability to acutely increase cardiac output during exercise4,5. Two hypotheses were tested: 1) CBFv would be similar in HTR when compared to age-matched controls (AM), but lower than young controls (YC); 2) that during exercise, the HTR would have reduced elevations in CBFv compared with AM and YC. Methods: 7 male clinically stable HTR (62 ± 9 yrs of age and 9 ± 7 yrs post-transplant), 7 male AM (62 ± 7 yrs), and 7 male YC (22 ± 3 yrs) were recruited for this study. Bilateral middle cerebral arteries were insonated transcranial Doppler ultrasound to obtain an index of CBFv. Data were obtained while seated (rest) and during a progressive cycling test to volitional exhaustion. A repeated measures ANOVA was applied to identify differences across exercise intensity. Comparisons between groups were performed with Fischer’s LSD post hoc test. Results: Table 1 provides an overview of the cerebrovascular, cardiovascular, and cardiorespiratory responses at rest and during the progressive exercise test. Conclusion: Following long-term HTR, CBFv are comparable to AM counterparts; therefore, at rest it is the age of the brain and its cerebral vasculature that affects CBF more so than the younger donor heart. Moreover, during progressive exercise, CBFv is well maintained in HTR.
Where applicable, experiments conform with Society ethical requirements