fMRI in CardiaC arrEst With Uncertain Prognosis

The goal of this observational study is to determine whether specific advanced MRI measures are associated with functional outcomes in patients who are comatose after cardiac arrest. The main question\[s\] it aims to answer are: Aim 1: Determine if stimulus-based functional MRI (fMRI)-measured activations are independently associated with favorable neurological outcomes after cardiac arrest Aim 2: Determine if resting state functional MRI (rs-fMRI)-measured functional network connectivity is independently associated with favorable neurological outcomes after cardiac arrest. Aim 3: Determine if diffusion tensor imaging (DTI)-measured white matter integrity is associated with favorable neurological outcomes after cardiac arrest. Participants will undergo advanced MRI sequences at time of clinical MRI, and will be followed for 6 months post-arrest.

Inclusion Criteria: * survive of an in or out of hospital cardiac arrest Exclusion Criteria: * Drug overdose * Opinion of medical team patient unlikely to survive more than 24 hours (severe concurrent medical illness, dilated and unreactive pupils, etc..) * Following verbal commands (MD or RN note) once TTM is complete and normothermia is achieved (Day 2 or 3; Day of admission is Hospital Day 0). If no TTM is administered, this can be assessed on Hospital Day 2. * Following verbal commands (study team assessment) at time of MRI * Family planning to WLST at time of enrollment * Non English speaker (okay if English not primary language, as long as they can understand it) * Permanent Contraindication to MRI (some kind of implanted metal) * Pregnant