Background: Stress response is tightly regulated by the autonomic nervous system (ANS) which can be measured by heart rate variability (HRV). Traditional risk factors and acute triggers for ischemic stroke and transient ischemic attack (TIA) are considered as chronic and acute stressors, respectively. These risk factors all contribute to the recurrent ischemic events and are related to ANS dysfunction. The moderate predictive value of ABCD2 score may be due to assessing a limited number of stressors.
Aims, Objectives and Hypotheses: We proposed to 1) assess whether HRV parameters, as markers of ANS function and stress, can predict secondary ischemic events after TIA or minor stroke, and 2) compare the HRV-based predictive tools with ABCD2 score. We expected that using HRV indicators can enhance the prediction of ischemic events.
Methods: This is a prospective observational study. Patients developed TIA or minor stroke within 48 hours were eligible. The main study variables included: ABCD2 score, HRV assessment from 24-hour Holter recording, and psychological stress. HRV measurement included calculations of both absolute values and changes of HRV frequency-domain parameters: high frequency (HF), normalized HF, HF +low frequency, and total power. Patients were followed for 90 days to assess the development of outcome events. Logistic regression was employed for data analyses. Area under the curve (AUC) and diagnostic tests were used to assess models’ predictive power.
Results: Final analyses include data collected from 201 patients. The most useful HRV predictors were Daytime HF changes (AUC=0.70) and Morning HF value (AUC=0.61). AUCs for the Best Stress Model and the Most Practical Model were 0.82 and 0.76, respectively, which were significantly higher than AUC of ABCD2 score (AUC=0.63), p <0.05. The optimal cut-off points for Daytime HF changes and Morning HF might be increase of 12.5% and 50 ms2, respectively. The exploratory models that involved both values and changes of HF had AUCs ≥0.82.
Conclusions: Assessing the effects of stress on ANS may be an innovative way to stratify the risk of TIA or minor stroke. Models using HRV parameters, especially HF, provide superior predictive values to ABCD2 score. Future research is needed to validate these results.