Should a patient with ST-Elevation Myocardial Infarction (STEMI) be heparinized?

Heparin Administration in STEMI Patients

Yes, patients with ST-Elevation Myocardial Infarction (STEMI) should be heparinized as part of standard treatment regardless of the reperfusion strategy chosen.

Primary PCI Strategy

For patients undergoing primary percutaneous coronary intervention (PCI):

• Unfractionated heparin (UFH) should be administered as a weight-adjusted intravenous bolus of 70-100 U/kg (maximum 5,000 U) when used alone 1
• A reduced dose of 60 U/kg (maximum 4,000 U) should be used when administered with glycoprotein IIb/IIIa inhibitors 1
• Target activated clotting time (ACT) should be 250-350 seconds (200-250 seconds with GPIIb/IIIa inhibitors) 1
• Heparin infusion is typically discontinued at the end of the primary PCI procedure 1

Fibrinolytic Therapy Strategy

For patients receiving fibrinolytic therapy:

• UFH should be administered as a 60 U/kg IV bolus (maximum 4,000 U) followed by an infusion of 12 U/kg/hour (maximum 1,000 U/hour) 2
• The infusion should be adjusted to maintain activated partial thromboplastin time (aPTT) at 1.5 to 2.0 times control (approximately 50 to 70 seconds) 2, 3
• Anticoagulation should continue for a minimum of 48 hours, and preferably for the duration of the index hospitalization, up to 8 days or until revascularization if performed 2
• For patients receiving fibrin-specific agents (alteplase, reteplase, tenecteplase), heparin is strongly recommended 2
• For patients receiving non-selective fibrinolytic agents (streptokinase), heparin is particularly important for those at high risk for systemic emboli (large or anterior MI, atrial fibrillation, previous embolus, or known LV thrombus) 2

No Reperfusion Therapy

For patients not receiving reperfusion therapy:

• UFH should still be given as soon as possible 2
• Weight-adjusted dosing of 60-70 U/kg IV bolus followed by 12-15 U/kg/hour infusion is recommended 3
• Angiography before hospital discharge is recommended, similar to patients after successful fibrinolysis 2

Benefits of Heparin Pretreatment

Recent evidence suggests additional benefits of early heparin administration:

• UFH pretreatment before arrival at the catheterization laboratory is associated with reduced all-cause mortality (OR = 0.61,95% CI: 0.49-0.76) 4
• Pretreatment is associated with lower in-hospital cardiogenic shock (OR = 0.68,95% CI: 0.58-0.78) 4
• Higher rates of spontaneous reperfusion events are observed with pretreatment (OR = 1.68,95% CI: 1.47-1.91) 4
• Pretreatment with UFH is associated with a reduction in coronary artery occlusion among STEMI patients, with a number needed to treat of 12 5

Monitoring and Safety Considerations

• For patients on fibrinolytic therapy, aPTT should be checked at 3,6,12, and 24 hours after initiation 1, 3
• Daily monitoring of platelet counts is recommended in patients receiving UFH 2
• More frequent monitoring of aPTT and full weight adjustment of heparin may decrease the risk of non-cerebral bleeding complications 1
• Excess heparin dosing is common (49% of patients in one study) and associated with higher rates of major bleeding and transfusion, particularly in patients with low body weight and female sex 6

Alternative Anticoagulants

• Enoxaparin (low-molecular-weight heparin) may be considered as an alternative to UFH in patients under 75 years of age receiving fibrinolytic therapy, provided significant renal dysfunction is not present 2
• For patients ≥75 years receiving enoxaparin, the initial bolus should be omitted and starting with 0.75 mg/kg SC every 12 hours is recommended 3
• Bivalirudin may be considered for patients with heparin-induced thrombocytopenia, with a recommended dose of 0.75 mg/kg IV bolus followed by 1.75 mg/kg/h infusion 7

Common Pitfalls to Avoid

• Overdosing heparin, especially in low-weight patients and women 6
• Using LMWH as an alternative to UFH in patients over 75 years receiving fibrinolytic therapy 3
• Failing to adjust heparin dosing when used with glycoprotein IIb/IIIa inhibitors 1
• Inadequate monitoring of anticoagulation parameters (aPTT or ACT) 3
• Discontinuing heparin too early in high-risk patients 2