The recommendations are limited to drugs, de- vices, and treatments approved for clinical use in the United States. Class of Recommendation and Level of Evidence The Class of Recommendation (COR) indicates the strength of the recommendation, encompassing the es- timated magnitude and certainty of benefit in propor- tion to risk. The Level of Evidence (LOE) rates the quality of scientific evidence that supports the intervention on the basis of the type, quantity, and consistency of data from clinical trials and other sources (Table 1).P-4 P-6 Glenn N. Levine, MD, FACC, FAHA Chair, ACC/AHA Task Force on Clinical Practice Guidelines 1.1. Methodology and Evidence Review The recommendations listed in this guideline are, whenever possible, evidence-based. An initial exten- sive evidence review, which included literature de- rived from research involving human subjects, pub- lished in English, and indexed in MEDLINE (through PubMed), EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other select- ed databases relevant to this guideline, was conduct- ed from April 2014 to November 2014. 