Do you still give a heparin (unfractionated heparin) bolus and drip to patients with Acute Myocardial Infarction (AMI) who are already on oral Coumadin (warfarin)?

Management of Heparin in AMI Patients on Oral Coumadin

For patients with Acute Myocardial Infarction (AMI) who are already on oral Coumadin (warfarin), a heparin bolus and drip should still be administered, especially in cases requiring immediate intervention such as primary PCI, but with dose adjustment based on the patient's anticoagulation status.

Rationale for Heparin Administration in AMI Patients on Coumadin

• Heparin is a standard anticoagulant therapy during primary PCI for AMI due to the strong belief that anticoagulation is required during the procedure, even in patients already on oral anticoagulants 1
• For patients with AMI requiring immediate cardioversion or intervention due to hemodynamic instability, heparin should be administered concurrently by an initial intravenous bolus followed by continuous infusion, regardless of prior anticoagulation status 1
• The primary goal of heparin therapy in AMI is to prevent early thrombotic complications during and immediately after intervention, which warfarin alone may not adequately address due to its delayed onset of action 1, 2

Recommended Approach for Heparin Administration

For AMI Patients on Coumadin Undergoing Primary PCI:

• Administer intravenous heparin bolus at a reduced dose of 60-70 U/kg (rather than the standard 100 U/kg) if the patient is already anticoagulated with warfarin 1
• Perform the procedure under activated clotting time (ACT) guidance, adjusting heparin to maintain an ACT of 250-350 seconds (or 200-250 seconds if GPIIb/IIIa inhibitors are used) 1
• Check INR prior to heparin administration if possible, and consider further dose reduction if INR is already in therapeutic range (2.0-3.0) 1, 2

For AMI Patients on Coumadin Not Undergoing Primary PCI:

• If fibrinolytic therapy is planned, carefully assess bleeding risk as combination of warfarin and heparin significantly increases bleeding risk 1
• For patients not receiving reperfusion therapy, intravenous heparin should still be administered as a bolus followed by weight-adjusted infusion with first aPTT control after 3 hours 1

Monitoring and Dose Adjustment

• More frequent monitoring of aPTT (every 4-6 hours initially) is recommended when administering heparin to patients already on warfarin 1, 3
• Target a lower aPTT range (1.5 times control rather than 1.5-2.5 times) in patients with therapeutic INR values 1, 3
• Monitor closely for signs of bleeding, particularly at vascular access sites during PCI 1

Special Considerations

• The risk of bleeding is increased when heparin is administered to patients already on warfarin, requiring careful assessment of the risk-benefit ratio 1, 2
• For patients with very high INR values (>3.5), consider omitting the heparin bolus and starting with a lower infusion rate 1, 3
• After the acute phase of AMI management, resume the patient's previous warfarin regimen with appropriate bridging as needed 2

Common Pitfalls to Avoid

• Failing to check the patient's baseline INR before administering heparin can lead to excessive anticoagulation and increased bleeding risk 1
• Administering standard heparin doses to patients already anticoagulated with warfarin significantly increases bleeding complications 1, 2
• Discontinuing warfarin completely during AMI management without a proper transition plan can increase thrombotic risk, especially in patients with mechanical heart valves or atrial fibrillation 1

Conclusion

While patients on oral Coumadin still require heparin during AMI management, especially for procedures like primary PCI, dose adjustment and careful monitoring are essential to balance antithrombotic efficacy with bleeding risk. The decision should be based on the patient's current anticoagulation status, the urgency of intervention, and the specific AMI management strategy being employed.