Heparin Dosing for Percutaneous Coronary Intervention
For patients undergoing PCI, administer unfractionated heparin (UFH) as a 70-100 U/kg IV bolus when no glycoprotein IIb/IIIa inhibitor is planned, or 50-60 U/kg when GP IIb/IIIa inhibitors are used, targeting an activated clotting time (ACT) of 250-300 seconds. 1
Dosing Algorithm Based on Clinical Context
Primary PCI for STEMI
- Without GP IIb/IIIa inhibitor planned: 70-100 U/kg IV bolus 2, 1
- With GP IIb/IIIa inhibitor: 50-60 U/kg IV bolus 2
- Target ACT: 250-300 seconds 1
PCI for NSTE-ACS or Elective PCI
- Standard dosing: 70-100 U/kg IV bolus 1, 3
- With prior anticoagulation: Additional UFH as needed to achieve ACT 250-300 seconds 1
- Target ACT: 250-300 seconds 1
Critical Monitoring Points
Measure ACT 5 minutes after heparin administration - approximately two-thirds of patients fail to achieve target ACT with initial standard dosing 4. If ACT <250 seconds, administer additional 50 U/kg boluses as needed 4.
Check baseline coagulation studies (aPTT, INR, platelet count) before initiating heparin, then monitor ACT during the procedure 5.
Special Populations Requiring Dose Adjustment
Obese Patients
Lower weight-based doses (closer to 70 U/kg) achieve target ACT more reliably in obese patients compared to standard dosing 6. Body mass index is the only significant covariate affecting heparin response after weight-based dosing 6.
Active Smokers
Active smoking independently predicts failure to achieve target ACT (adjusted OR 6.06) 4. These patients require higher cumulative heparin doses and closer ACT monitoring 4.
Women
Women typically require higher weight-adjusted doses (mean 97.6 U/kg vs 89 U/kg in men) to achieve target ACT 6.
Transitioning from Prior Anticoagulation
From Enoxaparin
- Last dose <8 hours ago: No additional enoxaparin needed 1, 7
- Last dose 8-12 hours ago: Give 0.3 mg/kg IV enoxaparin 1, 7
- >12 hours or only 1 dose given: Give 0.3 mg/kg IV enoxaparin 1
From Fondaparinux
Do not use fondaparinux alone to support PCI - add UFH with anti-IIa activity due to catheter thrombosis risk 1, 3, 1. Administer standard UFH bolus (85 U/kg, or 60 U/kg with GP IIb/IIIa inhibitors) 8.
From UFH Infusion
Administer additional boluses as needed based on ACT measurement to achieve target 250-300 seconds 1.
Alternative Anticoagulant: Bivalirudin
Bivalirudin is a Class I alternative to UFH in STEMI patients undergoing PCI (reduces mortality and bleeding) 1. For NSTE-ACS, bivalirudin is Class IIb (may reduce bleeding but mortality benefit not established) 1.
Bivalirudin dosing: 0.75 mg/kg bolus, then 1.75 mg/kg/h infusion during PCI 1. Post-PCI infusion of 1.75 mg/kg/h for 2-4 hours in primary PCI 1. Reduce infusion to 1 mg/kg/h if creatinine clearance <30 mL/min 1.
Common Pitfalls to Avoid
Do not use fondaparinux as sole anticoagulant for PCI - this is a Class III (Harm) recommendation due to catheter thrombosis risk 1, 3, 1, 9, 1.
Do not give UFH to patients already on therapeutic subcutaneous enoxaparin - this increases bleeding without benefit 9.
Do not assume standard dosing achieves therapeutic anticoagulation - only 35-49% of patients reach target ACT with initial recommended bolus 4, 6. ACT monitoring is mandatory.
Discontinue parenteral anticoagulation immediately after PCI unless ongoing indication exists 8.
Post-PCI Anticoagulation
UFH infusion is not routinely continued after uncomplicated PCI in patients on dual antiplatelet therapy 10. Continue anticoagulation only if there is a separate indication (e.g., atrial fibrillation, venous thromboembolism) 1.
The 2025 ACC/AHA guidelines 1 represent the most current evidence-based recommendations and supersede older dosing protocols. The weight-based approach with ACT-guided titration remains the standard of care, with bivalirudin as a reasonable alternative particularly in high bleeding-risk patients.