Heparin Therapy in Myocardial Infarction

Dosing Recommendations

For patients with ST-elevation myocardial infarction (STEMI), the American College of Cardiology recommends unfractionated heparin (UFH) administration as a weight-adjusted IV bolus of 60 U/kg (maximum 4000 U) followed by an initial infusion of 12 U/kg/hour (maximum 1000 U/hour), with dose adjustments to maintain activated partial thromboplastin time (aPTT) at 1.5 to 2.0 times control (approximately 50 to 70 seconds). 1, 2
For patients receiving fibrin-specific thrombolytics (alteplase, reteplase, tenecteplase), the American College of Cardiology recommends an initial bolus of 60 U/kg (maximum 4000 U) and initial infusion of 12 U/kg/hour (maximum 1000 U/hour). 1, 2
For patients undergoing primary PCI, the American College of Cardiology recommends an initial bolus of 60-70 U/kg IV and initial infusion of 12-15 U/kg/hour. 2
For patients not receiving reperfusion therapy, the American College of Cardiology recommends weight-adjusted dosing of 60-70 U/kg IV bolus followed by 12-15 U/kg/hour infusion. 2
Anticoagulation should continue until revascularization (if performed) or for the duration of hospital stay up to 8 days according to European Heart Journal guidelines. 3

The American College of Cardiology recommends checking aPTT 4-6 hours after initiation of therapy and after any dose change. 1
Daily monitoring of platelet counts is recommended in patients receiving UFH according to the American College of Cardiology. 1
During PCI procedures, additional boluses may be needed to maintain therapeutic anticoagulation according to the American College of Cardiology. 4, 5
For PCI procedures, ACT should be monitored with target 250-300 seconds with HemoTec device or 300-350 seconds with Hemochron device if no GP IIb/IIIa inhibitors are used, according to Circulation guidelines. 6
The American College of Cardiology emphasizes that weight-based dosing is critical as the effect of a given dose of heparin is primarily mediated by patient weight. 1, 2

For patients ≥75 years old receiving enoxaparin, the American College of Cardiology recommends omitting the initial bolus and starting with 0.75 mg/kg SC every 12 hours. 4, 5
For patients with renal dysfunction (CrCl <30 mL/min), the American College of Cardiology recommends reducing enoxaparin to 1 mg/kg once daily. 4, 5
Fondaparinux (2.5 mg IV followed by 2.5 mg SC daily) may be considered for patients with serum creatinine <3.0 mg/dL according to the American College of Cardiology. 4, 5
Bivalirudin may be considered for patients with heparin-induced thrombocytopenia according to the American College of Cardiology. 2

For patients undergoing CABG, Circulation guidelines recommend that heparin should not be discontinued prior to surgery. 6
The American College of Cardiology advises that elderly patients may require lower initial doses and more frequent monitoring due to increased bleeding risk. 2
The American College of Cardiology recommends that LMWHs should not be used as an alternative to UFH in patients over 75 years receiving fibrinolytic therapy. 2
Subcutaneous heparin (7500 U twice daily) may be considered for patients not at high risk for systemic embolism according to the American College of Cardiology. 7
UFH has a short half-life (approximately 1.5 hours) and immediate anticoagulant effect when given intravenously. 8