Heart rate variability monitoring for the detection of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage.

BACKGROUND: Delayed cerebral ischemia (DCI) is a major cause of impaired outcome after aneurysmal subarachnoidal hemorrhage (aSAH). In this observational cohort study we investigated whether changes in heart rate variability (HRV) that preced DCI could be detected. METHODS: Sixty-four patients with aSAHwere included. HRV data were collected for up to 10 days and analyzed off-line.Correlationwith clinical status and/or radiologic findings was investigated. A linear mixed model was used for the evaluation of HRVparameters over time in patients with and without DCI. Extended Glascow outcome scale score was assessed after 1 year. RESULTS: In 55 patients HRV data could be analysed. Fifteen patients developed DCI. No changes in HRV parameters were observed 24 h before onset of DCI. Mean of the HRV parameters in the first 48 h did not correlate with the development of DCI. Low/high frequency (LF/HF) ratio increased more in patients developing DCI (beta -0.07 (95% confidence interval,0.12-0.01);p=0.012). Lower STRDRR (standard deviation of RR intervals), RMSSD (root mean square of the successive differences between adjacent RR intervals),and total power(p=0.003, p=0.007 and p=0.004respectively) in the first 48 h was seen in patients who died within 1 year. CONCLUSION: Impaired HRV correlated with 1-year mortality and LF/HF ratio increased more in patients developing DCI. Even though DCI could not be detected by the intermittent analysis of HRV used in this study, continuous HRV monitoring may have potential in the detection of DCI after aSAH using different methods of analysis.