Activated Clotting Time During Percutaneous Coronary Intervention

Unfractionated heparin (UFH) has been used clinically as an anticoagulant since 1935.1,2 Thirty-one years later, the activated clotting time (ACT) was developed as a test for the diagnosis and management of patients with inherited coagulation disorders.3 Later, the ACT test was extensively used to monitor UFH therapy in patients undergoing cardiopulmonary bypass surgery or percutaneous coronary interventions (PCI). Although ACT is often seen as a crude and imprecise test that does not correlate with other coagulation tests,4 it remains the most commonly used point-of-care test to monitor UFH during PCI procedures. Guidelines recommend target ACT values within 200 to 250 s with planned use of glycoprotein IIb/IIIa inhibitors and 250 to 300 s (Hemotech device) or 300 to 350 s (Hemochron device) without planned use of glycoprotein IIb/IIIa inhibitors for the guidance of UFH therapy during primary PCI procedures.5 The reference range for the target ACT is mostly empiric6 or based on small-scale studies.7–9 With regard to the association between ACT values and thrombotic or bleeding complications after PCI, studies remain markedly divided. A meta-analysis of 6 randomized trials of patients undergoing PCI by Chew et al10 showed that the risk of ischemic events reduced progressively with increasing ACT levels. The lowest rate of bleeding (8.6%) was observed in the ACT range between 325 and 350 s and it increased to 12.4% at ACT 350 to 375 s. However, this study included a heterogeneous population of the patients with a broad range of indications for PCI and only a small minority of patients received coronary stents or antithrombotic therapy (ticlopidine or clopidogrel). As a consequence, the study does not reflect the current practice of PCI. Another meta-analysis of 4 randomized trials, more contemporary in terms of the use of …