Distinct Trajectories of Consciousness Recovery During Targeted Temperature Management in Out-of-Hospital Cardiac Arrest Survivors: A Cluster Analysis

Background and Objectives: Static prognostication in comatose out-of-hospital cardiac arrest (OHCA) survivors may overlook delayed recovery, risking premature withdrawal of life-sustaining therapy (WLST). This study aimed to identify distinct longitudinal phenotypes of consciousness recovery and determine the prevalence and characteristics of the Late Awakener phenotype. Materials and Methods: We applied K-means clustering to serial Glasgow Coma Scale motor scores (0, 24, 48, 72 h, Day 5) in 417 adult OHCA survivors treated with targeted temperature management at Seoul St. Mary’s Hospital (2009–2023). Results: Three distinct phenotypes emerged: Early Awakeners (n = 86, 20.6%), Late Awakeners (n = 54, 12.9%), and Non-Awakeners (n = 277, 66.4%). While Early Awakeners had 96.5% good neurological outcomes at 6 months, 79.6% of Late Awakeners also achieved good outcomes despite being indistinguishable from Non-Awakeners at 48 h (mean GCS motor score ≤ 2). Late Awakeners had significantly higher rates of shockable rhythms (72.2% vs. 21.3%, p < 0.001) compared to Non-Awakeners. Conclusions: The identification of a Late Awakener phenotype—comprising 13% of the cohort and one-third of all survivors with good outcomes—challenges early prognostic pessimism. An extended observation window of at least 5–7 days may be warranted for patients with shockable rhythms to avoid premature WLST, even when early motor responses are absent.