Thirty-four studies (22,584 patients) were included in the review. There were five randomised controlled trials (RCTs), three of which were subgroup analyses from larger trials and two that assessed clopidogrel exposure prior to surgery. There were 29 observational studies, comprising 17 retrospective studies and 12 prospective studies. The median quality rating was 10 stars (range 0 to 16 stars). Nineteen studies stated that enrolments were consecutive. Follow-up was one month post-surgery (where stated).
There was a higher risk of mortality (OR 1.6, 95% CI 1.30 to 1.96) and increased rates of reoperation (OR 2.32, 95% CI 1.76 to 3.06) in patients undergoing coronary artery bypass grafting surgery with recent clopidogrel exposure. There was also an increased length of intensive-care unit stay (mean difference 0.31 days, 95% CI 0.06 to 0.56) in patients with recent clopidogrel exposure, although this finding was unlikely to be clinically significant. There were no differences between clopidogrel and control groups for combined major cardiovascular events (stroke, myocardial infarction, or death).
Subgroup analyses of patients with acute coronary syndrome found that there was no difference between groups in postoperative myocardial infarction (OR 0.57, 95% CI 0.31 to 1.07) and stroke rates (OR 1.23, 95% CI 0.66 to 2.29).