A novel enoxaparin regime for ST elevation myocardial infarction patients undergoing primary percutaneous coronary intervention: A WEST sub‐study

Objective : To evaluate the anticoagulation effect of subcutaneous (SQ) and intravenous (IV) enoxaparin through systematic anti‐Xa sampling during primary PCI for acute STEMI. Background : Although appropriate anticoagulation is essential to maximize the efficacy and safety of primary PCI, the optimal dosing of enoxaparin in this setting is unclear. Methods : STEMI patients randomized to primary PCI received ASA, clopidogrel 300 mg and enoxaparin 1 mg/kg SQ at earliest point of care, including prehospital. Plasma anti‐Xa determination occurred just prior to and after primary PCI. Supplemental IV enoxaparin (0.3–0.5 mg/kg) and abciximab was encouraged prior to PCI. Results : The 1st anti‐Xa level 56 min (median, IQR 47–77) post SQ enoxaparin was 0.28 U/ml (0.23–0.41); 85% of patients (28/33) were <0.5 U/ml (the recommended therapeutic level). Following PCI, 126 min (118–185) after SQ enoxaparin in those without IV dosing (8/33) the 2nd anti‐Xa level was 0.44 U/ml (0.29–0.53); 6 of 8 patients remained <0.5 U/ml. With IV enoxaparin (25/33) the 2nd anti‐Xa was 0.96 U/ml (0.82–1.16) 97 min (82–109) after SQ enoxaparin: all were ≥0.5 U/ml and 2 had levels 1.5 U/ml. Conclusion : A single SQ enoxaparin dose fails to achieve anti‐Xa levels ≥0.5 U/ml in the majority of STEMI patients. When combined with a strategy of supplemental IV enoxaparin, adequate anti‐Xa levels were achieved in all patients with few having levels >1.5 U/ml. This regime of SQ injection with additional IV enoxaparin provides an attractive strategy enhancing effective early anti‐thrombotic therapy at first medical contact prior to primary PCI. © 2007 Wiley‐Liss, Inc.