Writing commit- tees are asked to perform a formal literature review; weigh the strength of evidence for or against particular tests, treatments, or procedures; and include estimates of expected outcomes where such data exist. Patient-specific modifiers, comorbidi- ties, and issues of patient preference that may influence the choice of tests or therapies are considered. When available, information from studies on cost is considered, but data on efficacy and outcomes constitute the primary basis for the rec- ommendations contained herein. In analyzing the data and developing recommendations and supporting text, the writing committee uses evidence-based methodologies developed by the Task Force.1 The Class of Recommendation (COR) is an estimate of the size of the treatment effect considering risks versus benefits in addi- tion to evidence and/or agreement that a given treatment or procedure is or is not useful/effective or in some situations may cause harm. The Level of Evidence (LOE) is an esti- mate of the certainty or precision of the treatment effect. The writing committee reviews and ranks evidence supporting O Gara et al 2013 ACCF/AHA STEMI Guideline e365 each recommendation with the weight of evidence ranked as LOE A, B, or C according to specific definitions that are included in Table 1. Studies are identified as observational, retrospective, prospective, or randomized where appro- priate. For certain conditions for which inadequate data are available, recommendations are based on expert con- sensus and clinical experience and are ranked as LOE C. When recommendations at LOE C are supported by histori- cal clinical data, appropriate references (including clinical reviews) are cited if available. For issues for which sparse data are available, a survey of current practice among the members of the writing committee is the basis for LOE C recommendations and no references are cited. 