From the Guidelines
For myocardial infarction (MI), the recommended unfractionated heparin (UFH) dosing is an initial intravenous bolus of 60 units/kg (maximum 4,000 units) followed by a continuous infusion of 12 units/kg/h (maximum 1,000 units/h) 1. The infusion should be adjusted to maintain an activated partial thromboplastin time (aPTT) of 1.5 to 2.0 times control (approximately 50 to 70 seconds) 1. Key points to consider in the management of UFH for MI include:
- Monitoring aPTT 6 hours after the initial bolus and dose adjustment, then every 6 hours until stable, and then daily 1
- Adjusting the infusion rate to maintain the target aPTT range
- Typical duration of therapy is 48 hours or until completion of percutaneous coronary intervention (PCI), though it may be extended in certain clinical scenarios
- Careful monitoring for signs of bleeding and regular platelet counts to detect heparin-induced thrombocytopenia 1 The most recent and highest quality study guiding this recommendation is from 2012, which emphasizes the importance of weight-based dosing and maintaining a therapeutic aPTT range to minimize the risk of recurrent thromboembolism and bleeding complications 1.
From the Research
Heparin Dosing for Myocardial Infarction (MI)
The recommended heparin (unfractionated heparin) dosing for myocardial infarction (MI) is as follows:
- An initial heparin bolus of 60 U/kg (maximum, 4000 U) followed by a 12-U/kg/h infusion (maximum 1000 U/h) is recommended with alteplase for ST-elevation myocardial infarction 2.
- When intravenous heparin is administered for myocardial infarction with non-ST elevation and unstable angina, an initial bolus of 60 to 70 U/kg (maximum, 5000 U) followed by a 12- to 15-U/kg/h infusion is recommended 2.
- The goal is to achieve an activated partial thromboplastin time of 50 to 70 seconds 2.
- Another study recommends a bolus dose of 5,000-10,000 units, followed by a continuous infusion to maintain the activated partial thromboplastin time at 1.5-2.5 times the control value, and should be continued for 5-10 days in most patients 3.
- A more aggressive weight-based UFH dosing strategy using higher maximum doses and infusion rates has also been evaluated, with a bolus of 60-unit/kg (or maximum 10,000 units) followed by an infusion of 12 units/kg/hr (or maximum 2250 units/hr) 4.
Key Considerations
- The choice of heparin dosing regimen may depend on the specific clinical context and patient characteristics, such as body weight and renal function 4, 5.
- Monitoring of activated partial thromboplastin time (aPTT) is crucial to ensure adequate anticoagulation and minimize the risk of bleeding 2, 4, 5.
- The use of heparin in combination with other antithrombotic agents, such as aspirin and glycoprotein IIb/IIIa antagonists, may increase the risk of bleeding 2.