Baroreflex sensitivity and heart rate variability are predictors of mortality in patients with aneurysmal subarachnoid haemorrhage

Object: We aimed to investigate the link between the autonomic nervous system (ANS) impairment, assessed using baroreflex sensitivity (BRS) and heart rate variability (HRV) indices, and mortality after aneurysmal subarachnoid haemorrhage (aSAH). Methods: A total of 57 patients (56 +/- 18 years) diagnosed with aSAH were retrospectively enrolled in the study, where 25% of patients died in the hospital. BRS was calculated using a modified cross correlation method. Time and frequency domain HRV indices were calculated from a time series of systolic peak intervals of arterial blood pressure signals. Additionally, cerebral autoregulation (CA) was assessed using the mean velocity index (Mxa), where Mxa > 0 indicates impaired CA. Results: Both BRS and HRV indices were lower in non survivors than in survivors. The patients with disturbed BRS and HRV had more extensive haemorrhage in the H-H scale (p =.040) and were more likely to die (p =.013) when compared to patients with the intact ANS. The logistic regression model for mortality included: the APACHE II score (p =.002; OR 0.794) and the normalised high frequency power of the HRV (p <.001; OR 0.636). A positive relationship was found between the Mxa and BRS (R = 0.48, p =.003), which suggests that increasing BRS is moderately strongly associated with worsening CA. Conclusion: Our results indicated that lower values of HRV indices and BRS correlate with mortality and that there is a link between cerebral dysautoregulation and the analysed estimates of the ANS in aSAH patients.