Dual antiplatelet therapy in patients with aspirin resistance following coronary artery bypass grafting: study protocol for a randomized controlled trial [NCT01159639]

BACKGROUND: Coronary artery disease remains the dominant cause of mortality in developed countries. While platelets have been recognized to play a pivotal role in atherothrombosis, the ideal antiplatelet regime after coronary artery surgery remains elusive. The evolution of CABG has presently moved beyond technical improvements to involve modulation of pharmacologic management designed to improve patient outcomes. The aim of this trial will be to test the hypothesis that the addition of clopidogrel to patients with documented postoperative aspirin resistance will reduce the incidence of major cardiovascular events. ----- METHODS: Patients scheduled for isolated coronary artery surgery will be eligible for the study. Patients in whom postoperative multiple electrode aggregometry documents aspirin resistance will be randomized into two groups. The control group will receive 300 mg of aspirin. The dual antiplatelet group will receive 75 mg of clopidogrel in addition to 300 mg of aspirin. Patients will be followed for 6 months. Major adverse cardiac and cerebrovascular events (death from any cause, myocardial infarction, stroke, hospitalization due to cardiovascular pathology) as well as bleeding events will be recorded. ----- DISCUSSION: This will be the first trial that will specifically address the issue of dual antiplatelet therapy in patients undergoing coronary artery surgery who have been found to be aspirin resistant. In the event that the addition of clopidogrel proves to be beneficial in this subset of surgical patients, this study could significantly impact their future antiplatelet management. This randomized controlled trial has been registered at the ClinicalTrials.gov website (Identifier NCT01159639)

Bleeding risk assessment using multiple electrode aggregometry in patients following coronary artery bypass surgery

Individual variability in the response to antiplatelet therapy (APT), frequently administered preoperatively, has been established by various platelet function assays and could reflect bleeding tendency after coronary artery bypass surgery (CABG). Our hypothesis is that multiple electrode whole-blood aggregometry (MEA) can identify patients at risk for excessive bleeding. We enrolled 211 patients (155 male and 56 female) undergoing isolated CABG in a prospective observational study. Patients were divided into four groups with respect to their preoperative APT management. MEA, using the ASPI and the ADP test, was performed prior to surgery. The primary endpoint was chest tube output (CTO) and the secondary endpoint was perioperative packed red blood cell concentrate (PRBC) administration. Patients were characterized as bleeders if their 24 h CTO exceeded the 75th percentile of distribution. 24 h CTO value of 11.33 ml/kg presented 75th percentile of distribution, thus cut-off value for "bleeder category". The proportion of patients characterized as bleeders was significantly different among the groups in regard to preoperative APT (p = 0.039). Significant differences in both ASPI (p < 0.001) and ADP (p = 0.038) tests were observed between different preoperative APT groups. Significant correlations between the ASPI test (r = -0.170, p = 0.014) and ADP test (r = -0.206, p = 0.003) with 24 h CTO were found. The receiver operating curve revealed an ASPI test value of <20 area under curve (AUC) units (AUC 0.603, p = 0.023) and an ADP test <73 AUC (AUC 0.611, p = 0.009) as a "bleeder" determinant. The proportion of patients transfused with PRBC did not significantly differ among the groups in regard to preoperative APT (p = 0.636). Comparison of the ASPI test values between patients with respect to PRBC administration revealed lower values in the ASPI test in a group of patients transfused with PRBC (mean, 27.88 vs. 40.32 AUC, p = 0.002). Our study showed that MEA is a useful method of predicting CABG patients with excessive postoperative bleeding