Endoh H, et al. - Whether prognostication of poor neurological outcome via heart rate variability (HRV) analysis is possible in comatose patients undergoing hypothermic targeted temperature management (TTM), was determined. This study was performed on prospectively included adult patients who were successfully resuscitated for out-of-hospital sudden cardiac arrest in the emergency department and were admitted to the intensive care unit of the Niigata University in Japan, during the time frame of January 2015 to December 2017. The factors that significantly predicted poor outcome were ln (natural logarithm) very-low frequency (ln VLF) power and detrended fluctuation analysis (DFA) (α1), as revealed in the multivariate logistic regression analysis of 3 variables. For the prediction of poor outcome, an area under the receiver operating characteristic curve of 0.84 and 0.82 was generated for ln VLF power and DFA (α1), respectively. Based on the findings, the possible utility of HRV analysis for prognostication for comatose patients during hypothermic TTM was suggested.