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Introduction: Since thrombolytic drugs such as streptokinase could cause reocculsion, anticoagulants like heparin are utilized afterwards. Several nomograms have been recommended due to unpredictable pharmacokinetics of heparin. Therefore, this study aimed to compare two prevalent nomograms of   heparin used in patients suffering from acute myocardial infarction (AMI) after recieving streptokinase.

Methods: In this single-blind randomized clinical trial, 113 patients with AMI were randomly assigned to one of the two nomogram groups four hours after receiving streptokinase. Patients in the group1(n=50), received an initial infusion with  rate of 17 U/Kg/hr and a bolus of 80 U/Kg. In Group 2(n=35), the initial rate of heparin (n= 53) was 12 U/Kg/hr with a maximum 900U/hr after a bolus of 60 U/Kg with a maximum of 4000 U. Activated Partial Thromboplastin Time (aPTT) was measured every 6 hours for at least 48 hours and infusion rate was adjusted  based on each nomogram in order to maintain aPTT in the therapeutic level of 46-70 s.

Results: Patients in the two groups were homogenized in regard with their demographic characteristics. The time needed for aPTT to pass the infusion threshold for groups 1 and 2 were 8.00±3.81 hr and 11.12±5.55 hr, respectively (p=0.00). In the first 12 hours, percentages of patients, whose aPTT was reported in an apporpriate therapeutic range were 56.0% and 30.19% for the two groups, respectively (p=0.00). Moreover, period of time that subjects in group 1 were in the therapeutic range in the first 24 and 48 hours was 14.40 ± 6.42 hrs and 27.48 ± 9.90 hrs, respectively. While these numbers for group 2 were 9.74±3.08 hrs and 21.06 ± 9.42 hrs, respectively (P=0.00, P=0.00). The changes in the heparin rate was reported significantly lower in  group 1 compared to  group 2.

Conclusion: The study findings revealed that nomogram 1 is preferred to nomogram 2, since patients in nomogram 1 reached the therapeutic range faster, stayed in this range for a longer period of time, and needed less change in the heparin rate