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 in ASA responders.


OBJECTIVE
To conduct a prospective, multicentre observational pilot study to determine the thrombotic event rates in ASA responders and nonresponders.


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 effect (or lack thereof) on their bleeding times. All thrombotic events that occurred in the two years following CABG were recorded. These data were stored in a blinded fashion until the last patient follow-up, and then adjudicated 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% had thrombotic events compared with 9.5% of the ASA nonresponders, but this difference was not significant (P=0.526).


CONCLUSIONS
While ASA responder or nonresponder status did not appear to affect the thrombotic event rate in patients undergoing nonurgent CABG, the possibility that ASA responder or nonresponder status affects the thrombotic event rate in more acutely ill CABG patients cannot be excluded.
Buchanan
M R
MR
McMaster University Health Sciences Centre, Hamilton, Canada. mbuchan@fhs.mcmaaster.ca
Schwartz
L
L
Bourassa
M
M
Brister
S J
SJ
Peniston
C M
CM
D001241:Aspirin / Q000627:therapeutic use*; D001760:Bleeding Time; D001026:Coronary Artery Bypass; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D011446:Prospective Studies; D012307:Risk Factors; D013927:Thrombosis / Q000209:etiology / Q000517:prevention & control*; D013928:Thromboxane A2 / Q000097:blood
D010975:Platelet Aggregation Inhibitors; D013928:Thromboxane A2; D001241:Aspirin