The investigators will conduct a prospective, international, observational study of cardiac arrest survivors using guideline-recommended prognostic assessment tools with central adjudication of results, while avoiding premature withdrawal of life-sustaining therapy (WLST). The investigators will prospectively collect data on demographics, premorbid characteristics, details of cardiac arrest and resuscitation, post-cardiac arrest care, detailed neurological examination findings, electrophysiologic studies, chemical biomarkers and neuroimaging at standardized time points, and will assess functional outcomes at discharge, 6- and 12-month follow-up, as well as annually up to 5 years. The international cohort will have a derivation subset that will be used to create a multimodal outcome prediction model (using regression analysis), which will then be confirmed by the validation subset. A substudy of MOCHA will also explore the impact of the practice of WLST in the prediction model by analyzing its performance in a pooled cohort of subjects unexposed to WLST originating from countries where this practice is not common.