Comparison of MAX-ACT and K-ACT values when using bivalirudin anticoagulation during minimally invasive hybrid off-pump coronary artery bypass graft surgery

Objective: To compare the kaolin-activated coagulation time (K-ACT) to the MAX-ACT for monitoring anticoagulation with bivalirudin in patients undergoing hybrid off-pump coronary artery revascularization procedures. Design: A prospective, observational study. Setting: A cardiac surgical operating room of a university-affiliated hospital. Participants: Twelve patients undergoing off-pump coronary artery bypass graft surgery and percutaneous coronary intervention during the same procedure anticoagulated with bivalirudin to a target K-ACT of >300 seconds. Intervention: At baseline and at frequent intervals during anticoagulation, K-ACT and MAX-ACT assays were run contemporaneously, and the pairs of results were analyzed with descriptive statistics, by correlation analysis, and with Bland-Altman analysis. Measurements and Main Results: The MAX-ACT and K-ACT assays were highly correlated, but the MAX-ACT assay consistently reported significantly lower ACT values compared with the K-ACT. The mean bias (K-ACT minus MAX-ACT) was 94 seconds (limits of agreement, 51-138 seconds). Conclusion: To maximize patient safety, centers using bivalirudin for anticoagulation during cardiac surgical procedures need to be aware of the different performance characteristics of ACT assay subtypes.