Out-of-hospital Cardiac Arrest (OHCA) Biomarkers

Inclusion Criteria: \- \>18 years old Study cohort: * Non-traumatic out of hospital cardiac arrest * Control cohort: * Chest pain of non-cardiac etiology Exclusion Criteria: Both cohorts: * Females of child bearing age with positive pregnancy test * Neurodegenerative disease or other neurological disorder (dementia, Parkinson's disease, multiple sclerosis, seizure disorder, or brain tumours) * History of neurosurgery within the last 30 days Acute brain injury within the last 30 days (ischemic/ haemorrhagic stroke, traumatic brain injury) Subject is anemic OR donated blood within the last 8 weeks OR has a hematological disorder that requires transfusions Subject has history of liver failure OR renal failure Study cohort: Advanced directives against resuscitation Traumatic cardiac arrest In hospital cardiac arrest Failure to attain ROSC + visible signs of death (livor mortis, rigor mortis) Control cohort: EKG changes: New ST-elevation consistent with myocardial infarction NSTEMI Hemodynamically unstable