Results of the BRAT study - A pilot study investigating the possible significance of ASA nonresponsiveness on the benefits and risks of ASA on thrombosis in patients undergoing coronary artery bypass surgery

BACKGROUND: Several studies suggest that acetylsalicylic acid (ASA) is less effective in preventing thrombotic events in ASA nonresponder patients. If so, the thrombotic event rate in ASA nonresponders should be higher than i n ASA responders. OBJECTIVE: To conduct a prospective, multicentre observational pilot study to determine the thrombotic event rates in ASA responders and nonresponders . PATIENTS AND METHODS: Patients undergoing nonurgent coronary artery bypass grafting (CABG) who were prescribed 325 mg ASA/day were recruited. Patients were classified as an ASA responder or nonresponder based on the ASA effec t (or lack thereof) on their bleeding times. All thrombotic events that occ urred in the two years following CABG were recorded. These data were stored in a blinded fashion until the last patient follow up, and then adjudicate d by a validation committee. RESULTS: A total of 289 patients recruited at three sites completed the two -year follow-up. Of these patients, 45.3% were classified as ASA responders and 54.7% were classified as ASA nonresponders. Of ASA responders, 6.9% ha d thrombotic events compared with 9.5% of the ASA nonresponders, but this d ifference was not significant (P=0.526). CONCLUSIONS: While ASA responder or nonresponder status did not appear to a ffect the thrombotic event rate in patients undergoing nonurgent CABG, the possibility that ASA responder or nonresponder status affects the thromboti c event rate in more acutely in CABG patients cannot be excluded.