The activated clotting time (ACT) can be used to monitor enoxaparin and dalteparin after intravenous administration.

BACKGROUND The use of low-molecular weight heparin (LMWH) during percutaneous coronary intervention (PCI) has been limited by the presumed inability to monitor its anticoagulant effect using bedside assays. OBJECTIVES This study was designed to compare the dose-response of enoxaparin, dalteparin and unfractionated heparin (UFH) on the activated clotting time (ACT), and to determine whether the ACT or aPTT can be used to monitor intravenous (IV) low molecular weight heparin (LMWH). METHODS A total of 130 patients undergoing cardiac catheterization were assigned to intravenous enoxaparin 0.5 mg/kg, dalteparin 50 international units/kg or UFH 50 units/kg. Of the 130 patients, 46 (35%) underwent PCI, all of whom received a glycoprotein (GP) IIb/IIIa inhibitor. We measured ACT, activated partial thromboplastin time (aPTT) and plasma anti-Xa levels after serial sampling. RESULTS Both enoxaparin and dalteparin induced a significant rise in the ACT and aPTT, with an ACT dose-response approximately one-half the magnitude of that obtained using UFH. The time course of changes in the ACT and aPTT after administration of enoxaparin and dalteparin was virtually identical, with a return to baseline at approximately 2 hours. The enoxaparin and dalteparin-treated patients successfully underwent PCI with no major hemorrhagic complications. CONCLUSIONS The ACT is equally sensitive to IV enoxaparin and dalteparin. These data support an ACT-guided strategy for intravenously administered LMWH during PCI. Additional studies with larger patient populations may be indicated to determine the ideal target ACT for LMWH in PCI.