Purpose: The aim of this study was to find an optimal range of activated clotting time (ACT) during off-pump coronary artery bypass surgery (OPCAB) yielding ischemic protection without the risk of hemorrhagic complications in patients with recent exposure to dual antiplatelet therapy. Materials and Methods: Three hundred and five patients who received aspirin and clopidogrel within 7 days of isolated multi-vessel OPCAB were retrospectively studied. Combined hemorrhagic and ischemic outcome was defined as the occurrence of 1 of the following: significant perioperative bleeding (>30% of estimated blood volume), transfusion of packed red blood cell (pRBC) ≥2 U, or myocardial infarction (MI). This was compared in relation to the tertile distribution of the time-weighted average ACT-212-291 sec (first tertile), 292-334 sec (second tertile), 335-485 sec (third tertile). Results: The amount of perioperative blood loss was 937±313 mL, 1014±340 mL, and 1076± 383 mL, respectively (p=0.022). Significantly more patients in the third tertile developed MI (4%, 4%, and 12%, respectively, p=0.034). The incidence of significant perioperative blood loss and transfusion of pRBC ≥2 U were lower in the first tertile than those of other tertiles without statistical significance. In the multivariate analysis, the first tertile was associated with a 52% risk reduction of combined hemorrhagic and ischemic outcomes (95% confidence interval: 0.25-0.92, p= 0.027). Conclusion: A lower degree of anticoagulation with a reduced initial heparin loading dose should be carefully considered for patients undergoing OPCAB who have recently been exposed to clopidogrel.
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