For more than 3 decades, the American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Practice Guidelines has contributed substantially to the quality of cardiac care by developing guidelines pertaining to virtually all areas of cardiovascular disease. The intent is to provide health care professionals inundated by an ever-expanding medical literature with the evidence required for optimal patient care. ACC/AHA guidelines are revised and updated periodically, often in collaboration with other professional societies, to keep the documents current and relevant as new knowledge emerges. The purpose of guidelines is to inform clinical practice through a series of recommendations that codify the body of evidence on the disease in question according to the strength (class) of the recommendation and its underpinning level of evidence (LOE).