Clinical studyBeat-to-beat blood pressure variability and heart rate variability in relation to autonomic dysregulation in patients with acute mild-moderate ischemic stroke
Introduction
Impaired autonomic function is frequently seen in patients with ischemic stroke, and is associated with worse functional outcome and increased mortality [1], [2], [3]. Using Ewing’s battery of five autonomic function tests, which is considered a standard for diagnosis of autonomic dysregulation, our previous studies showed that the prevalence of severe autonomic dysregulation may reach 76.5% in patients after acute ischemic stroke, is related to an unfavorable functional outcome, and may persist up to six-months after stroke [4], [5]. This battery was divided into five groups depending on the number of abnormal or borderline result to allow classification of autonomic dysregulation [6]. Currently, the Ewing’s battery is not performed routinely, because administering all five of the required tests is very time-consuming and requires considerable cooperation from patients. Therefore, autonomic dysregulation is underdiagnosed in this population due to a lack of simpler diagnostic tools.
Non-invasive analysis of spontaneous heart rate variability (HRV) and blood pressure variability (BPV) has been widely used to assess autonomic function in many studies [7], [8]. BPV is also found to be a strong predictor of stroke and coronary events [9], [10], and unstable BPV is related to a poor outcome at 30 days following ischemic stroke [7]. However, there are no generally accepted cut-off values of each parameter in BPV and HRV to discriminate normal and impaired autonomic function. For this study, we hypothesized that BPV and HRV are alternatives to autonomic dysregulation measure in patients with ischemic stroke. To test this, we correlated BPV and HRV with the Ewing’s battery in this patient population and determined the sensitivity and specificity of BPV and HRV for diagnosis of autonomic dysregulation.
Section snippets
Subjects
This was a case-control observational study. Consecutive acute ischemic stroke patients within 7 days after onset were enrolled in Prince of Wales Hospital in Hong Kong between July 2015 and November 2016. Patients were included in the study only if they fulfilled all the following criteria: (1) age ≥18 years old; (2) Computed tomography (CT) or magnetic resonance imaging (MRI) showed cerebral ischemic stroke. None of the patients had insular involvement of their stroke lesions. Diagnosis of
Baseline characteristics of controls and acute stroke patients
A total of 13 healthy controls (6 males; mean age 59.46 years) and 53 acute ischemic stroke patients (45 males; mean age 65.34 years; mean National Institutes of Health stroke scale score on admission 5.90) were recruited. According to Ewing classification, all the patients were categorized into two groups: group 1 was diagnosed as minor (Normal or Early) autonomic dysregulation and group 2 was diagnosed as significant (Definite, Severe or Atypical) autonomic dysregulation. After recruitment,
Discussion
In this study, using Ewing’s battery to classify the autonomic dysregulation in acute ischemic stroke, we found that patients with significant autonomic dysregulation showed lower LF/HF RRI, LF BPV and LF/HF BPV. 75.47% acute ischemic stroke patients were diagnosed as significant autonomic dysregulation, which is consistent with our previous reports [4], [5]. To the best of our knowledge, very few studies have addressed the possible underlying mechanism how the autonomic dysregulation causes
Funding
This study was funded by the National Key R&D Program of China (2016YFC1301605) and Health and Medical Research Fund, Hong Kong SAR, China (reference no.02130836).
Acknowledgements
We would like to acknowledge the Lui Chi Woo Institute of Innovative Medicine, SH Ho Center for Cardiovascular Disease and Stroke Center, and Kwok Tak Seng Center for Stroke Research and Intervention, The Chinese University of Hong Kong.
Author contributions
GT analyzed data and drafted the manuscript. LX conceived, designed the project and performed all experiments. HL, YS, TL and LKW helped recruit patients.
Disclosure statement
The authors have no conflicts of interest to disclose.
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