PREAMBLE Since 1980, the American College of Cardiology (ACC) and American Heart Association (AHA) have translated sci- entific evidence into clinical practice guidelines with recom- mendations to improve cardiovascular health. These guide- lines, which are based on systematic methods to evaluate and classify evidence, provide a foundation for the delivery of quality cardiovascular care. The ACC and AHA sponsor the development and publication of clinical practice guide- lines without commercial support, and members volunteer their time to the writing and review efforts. Guidelines are official policy of the ACC and AHA. For some guidelines, the ACC and AHA partner with other organizations. Intended Use Clinical practice guidelines provide recommendations applicable to patients with or at risk of developing car- diovascular disease. The focus is on medical practice in the United States, but these guidelines are relevant to patients throughout the world. Although guidelines may be used to inform regulatory or payer decisions, the in- tent is to improve quality of care and align with patients interests. Guidelines are intended to define practices meeting the needs of patients in most, but not all, cir- cumstances, and should not replace clinical judgment. Clinical Implementation Management, in accordance with guideline recom- mendations, is effective only when followed by both practitioners and patients. Adherence to recommen- dations can be enhanced by shared decision-making between clinicians and patients, with patient engage- ment in selecting interventions on the basis of individ- ual values, preferences, and associated conditions and comorbidities. Methodology and Modernization The ACC/AHA Joint Committee on Clinical Practice Guidelines (Joint Committee) continuously reviews, up- dates, and modifies guideline methodology on the ba- sis of published standards from organizations, including the Institute of Medicine,1,2 and on the basis of internal reevaluation. 