Sympathovagal imbalance in early ischemic stroke is linked to impaired cerebral autoregulation and increased infarct volumes

  • Pedro Castro
    Corresponding author at: Centro Hospitalar Universitário São João, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal.
    Cardiovascular Research and Development Center, Faculty of Medicine of University of Porto, Porto, Portugal

    Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
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  • Jorge Serrador
    The MARCS Institute for Brain, Behaviour and Development, Western Sydney University, Sydney, Australia

    Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, NJ, USA

    National University of Ireland Galway, Galway, Ireland
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  • Farzaneh Sorond
    Department of Neurology, Division of Stroke and Neurocritical, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
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  • Elsa Azevedo
    Cardiovascular Research and Development Center, Faculty of Medicine of University of Porto, Porto, Portugal

    Department of Neurology, Centro Hospitalar Universitário de São João, Porto, Portugal
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  • Isabel Rocha
    Cardiovascular Autonomic Function Lab, Institute of Physiology, Faculty of Medicine of University of Lisbon, Portugal
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      • We examined 26 patients with acute ischemic stroke within 6 hours from symptom-onset and assessed non-invasively heart rate variability, baroreflex sensitivity and dynamic cerebral autoregulation
      • Increased heart rate spectral power towards high frequencies (tonic parasympathetic) and baroreflex sensitivity (reflex parasympathetic) were correlated with higher gain, thus worse cerebral autoregulation
      • Predominant vagal activity was associated with the development of larger infarct volumes
      • The modulation of autonomic and vagal activity should be subject to study in acute ischemic stroke


      Background and purpose

      Autonomic dysfunction is associated with worse outcome of ischemic stroke patients by mechanisms that are not fully understood. There is evidence of autonomic influence in cerebrovascular control but this has not been studied in acute stroke. Therefore, we examined the relationship between heart rate variability (HRV) and baroreflex sensitivity (BRS) in dynamic cerebral autoregulation in the early hours post ischemia, and its impact in clinical and radiological outcome.


      We prospectively enrolled 26 patients with acute ischemic stroke in middle cerebral artery. Arterial blood pressure (Finometer), cerebral blood flow velocity (transcranial Doppler), and electrocardiogram were recorded within 6 h. HRV was assessed by the standard side deviations of normal inter-beat intervals, spectral analysis and non-linear entropy indexes. Spontaneous BRS was assessed by spectral and sequence methods. Dynamic cerebral autoregulation was assessed by transfer function analysis (coherence, phase and gain). Infarct volume was calculated from computed tomography at 24 h. Clinical outcome was assessed by the modified Rankin scale.


      Increased BRS and HRV high frequencies power, both reflecting increased vagal modulation, were correlated with higher gain values of cerebral autoregulation (p < 0.05). The higher vagal modulation was also associated with later large infarct volumes (p < 0.05) but not with clinical outcome.


      Increased vagal modulation in early hours of acute ischemic stroke, may interfere with cerebrovascular control and is associated with larger infarcts. Understanding the mechanisms that govern this complex interplay can be useful as novel therapeutic targets to improvement of outcome.


      dCA (dynamic cerebral autoregulation), HRV (heart rate variability), BRS (baroreflex sensitivity), IS (ischemic stroke), MAP (mean arterial blood pressure), RR (heart period between R-peaks)


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