Assessment of Activated Partial Thromboplastin Time Level in Patients with Acute Myocardial Infarction Receiving Fixed-Dose Intermittent Intravenous Heparin Therapy

Introduction- Heparin is one of the current and necessary medications in acute myocardial infarction (MI). Given the narrow therapeutic dose and unpredictable pharmacokinetics of heparin, its anticoagulant effect should be measured precisely. Despite the widespread utilization of heparin in intermittent fixed doses and weight-independent IV administration, our data about the range of aPTT as a monitoring marker are quite limited. Thus we prepared this study to measure if the custom method fills the target therapeutic range. Methods- This cross-sectional study was performed on 144 patients admitted to our department with acute MI in 2004, who received heparin 5000 units q4h and had daily aPTT checked on three consecutive days. We chose the second day samples for this study, and the data were gathered by a checklist and analyzed with SPSS software. Results- 12.5% of patients had aPTT levels in the therapeutic range, 6.2% of patients had a mean aPTT level above therapeutic range and remarkably, 81.3% of patients never achieved the therapeutic range. Our results also demonstrated that older age and female sex are associated with higher aPTT levels, and smoking unlike diabetes is associated with lower aPTT levels. Conclusion- Despite tolerability by patients and staff, the above findings necessitate reconsideration in the dose and interval of customary heparin administration (5000 unit IV q4h) and changing to continuous infusion method or use of low molecular weight heparins (Iranian Heart Journal 2007; 8 (2): 22-25).