Heart rate variability for the evaluation of patients with disorders of consciousness

Objective: Clinical responsiveness of patients with a Disorder of Consciousness (DoC) correlates to sym-pathetic/parasympathetic homeostatic balance. Heart Rate Variability (HRV) metrics result in non-invasive proxies of modulation capabilities of visceral states. In this work, our aim was to evaluate whether HRV measures could improve the differential diagnosis between Unresponsive Wakefulness Syndrome (UWS) and Minimally Conscious State (MCS) with respect to multivariate models based on standard clinical electroencephalography (EEG) labeling only in a rehabilitation setting.Methods: A prospective observational study was performed consecutively enrolling 82 DoC patients. Polygraphic recordings were performed. HRV-metrics and EEG descriptors derived from the American Clinical Neurophysiology Society's Standardized Critical Care terminology were included. Descriptors entered univariate and then multivariate logistic regressions with the target set to the UWS/MCS diagno-sis.Results: HRV measures resulted significantly different between UWS and MCS patients, with higher val-ues being associated with better consciousness levels. Specifically, adding HRV-related metrics to ACNS EEG descriptors increased the Nagelkerke R2 from 0.350 (only EEG descriptors) to 0.565 (HRV-EEG com-bination) with the outcome set to the consciousness diagnosis.Conclusions: HRV changes across the lowest states of consciousness. Rapid changes in heart rate, occur-ring in better consciousness levels, confirm the mutual correlation between visceral state functioning patterns and consciousness alterations. Significance: Quantitative analysis of heart rate in patients with a DoC paves the way for the implemen-tation of low-cost pipelines supporting medical decisions within multimodal consciousness assessments.CO 2023 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.