Because the ACC/AHA practice guidelines address patient populations (and healthcare providers) residing in North America, drugs that are currently unavailable in NorthAmerica are discussed in the text without a specific COR. For studies performed in large numbers of subjects outside NorthAmerica, a writing committee reviews the potential impact of different practice patterns and patient populations on the treatment effect and relevance to the ACC/AHA target population to determine whether the findings should inform a specific recommendation. The ACC/AHA practice guidelines are intended to assist healthcare providers in clinical decision making by describing a range of generally acceptable approaches to the diagnosis, management, and prevention of specific diseases or conditions. Theguidelinesareintendedtodefinepracticesthatmeettheneeds of most patients in most circumstances. The ultimate judgment about care of a particular patient must be made by the healthcare provider and patient in light of all the circumstances presented by that patient. As a result, situations may arise in which deviations from these guidelines are appropriate. In clinical decision mak- ing, consideration should be given to the quality and availability of expertise in the area where care is provided.When these guide- lines are used as the basis for regulatory or payer decisions, the goal should be improvement in quality of care. Prescribed courses of treatment in accordance with these rec- ommendations are effective only if they are followed. Because lack of patient understanding and adherence may adversely Table 1. Applying Classification of Recommendations and Level of Evidence A recommendation with Level of Evidence B or C does not imply that the recommendation is weak. Many important clinical questions addressed in the guidelines do not lend themselves to clinical trials. Although randomized trials are unavailable, there may be a very clear clinical consensus that a particular test or therapy is useful or effective. 