Applying Classification of Recommendation 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. *Data available from clinical trials or registries about the usefulness/efficacy in different subpopulations, such as sex, age, history of diabetes, history of prior myocardial infarction, history of heart failure, and prior aspirin use. For comparative effectiveness recommendations (Class I and IIa; Level of Evidence A and B only), studies that support the use of comparator verbs should involve direct comparisons of the treatments or strategies being evaluated. Kulik et al Secondary Prevention After CABG 929 in patients with ischemic heart disease.4,5 Over 30 years of experience has accrued with the use of aspirin after cardiac surgery, and essentially all patients undergoing CABG are candidates for long-term aspirin therapy.6 Aspirin inhibition of platelet function after CABG helps maintain graft patency and prevent major adverse cardiovascular events. Aspirin sig- nificantly improves vein graft patency rates, particularly dur- ing the first postoperative year. Preoperative aspirin use is safe and appears to reduce CABG operative morbidity and mortal- Therefore, aspirin should ideally be initiated before surgery at the time of hospital admission (with acute coronary syndrome or MI) or when CAD is first diagnosed.5,9,10 Considerable research has been performed to evaluate the impact of different dosing regimens and initiation times on post-CABG graft patency. The first randomized trials on the subject were conducted in the late 1970s, demonstrating that aspirin was safe for use in the postoperative period. 