A 68-year-old man is admitted to the ICU following out-of-hospital cardiac arrest with return of spontaneous circulation after 18 minutes of CPR. After 72 hours of targeted temperature management at 33°C, he remains deeply comatose with absent brainstem reflexes. His EEG shows the pattern marked **A** in the diagram — alternating bursts of high-amplitude polymorphic activity and flat suppression intervals. Which of the following best describes the clinical significance of this EEG finding in the context of post-arrest prognostication?