What is the recommended treatment regimen, including dose and duration, for myocardial infarction (Heart Attack)?

Treatment Regimen for Myocardial Infarction (Heart Attack)

The recommended treatment for myocardial infarction includes immediate administration of aspirin 162-325 mg loading dose, followed by a P2Y12 inhibitor (clopidogrel 600 mg, prasugrel 60 mg, or ticagrelor 180 mg), anticoagulation with unfractionated heparin or bivalirudin during primary PCI, and continued dual antiplatelet therapy for 1 year post-procedure. 1, 2

Initial Antiplatelet Therapy

• Aspirin 162-325 mg loading dose should be given immediately before primary percutaneous coronary intervention (PCI) 1, 2
• After PCI, aspirin should be continued indefinitely at a maintenance dose of 81-325 mg daily 1
• 81 mg daily is the preferred maintenance dose when used with ticagrelor 1
• A loading dose of a P2Y12 receptor inhibitor should be administered as early as possible or at the time of primary PCI with one of the following options:
  • Clopidogrel: 600 mg 1
  • Prasugrel: 60 mg 1
  • Ticagrelor: 180 mg 1

Anticoagulation During Primary PCI

• For patients undergoing primary PCI, the following anticoagulant regimens are recommended:
  • Unfractionated heparin (UFH): 50-70 U/kg IV bolus if GP IIb/IIIa receptor antagonist is planned; 70-100 U/kg bolus if no GP IIb/IIIa receptor antagonist is planned 1
  • Bivalirudin: 0.75 mg/kg IV bolus, then 1.75 mg/kg/h infusion with or without prior treatment with UFH 1
• Bivalirudin monotherapy is reasonable in patients at high risk of bleeding 1
• Fondaparinux should not be used as the sole anticoagulant for primary PCI due to risk of catheter thrombosis 1

Glycoprotein IIb/IIIa Inhibitors

• In selected patients, it is reasonable to administer intravenous GP IIb/IIIa receptor antagonists during primary PCI with UFH:
  • Abciximab: 0.25 mg/kg IV bolus, then 0.125 mcg/kg/min (maximum 10 mcg/min) 1
  • Tirofiban (high-bolus dose): 25 mcg/kg IV bolus, then 0.15 mcg/kg/min 1
  • Eptifibatide (double bolus): 180 mcg/kg IV bolus, then 2 mcg/kg/min; a second 180 mcg/kg bolus is administered 10 min after the first bolus 1

Maintenance Antiplatelet Therapy

• P2Y12 inhibitor therapy should be continued for 1 year in patients who receive a stent (bare-metal or drug-eluting) during primary PCI using the following maintenance doses:
  • Clopidogrel: 75 mg daily 1
  • Prasugrel: 10 mg daily 1
  • Ticagrelor: 90 mg twice daily 1
• Prasugrel should not be administered to patients with a history of prior stroke or transient ischemic attack 1

Stent Selection Considerations

• Bare-metal stents should be used in patients with high bleeding risk, inability to comply with 1 year of dual antiplatelet therapy, or anticipated invasive or surgical procedures in the next year 1
• Drug-eluting stents should not be used in patients unable to tolerate or comply with a prolonged course of dual antiplatelet therapy due to increased risk of stent thrombosis 1

Beta-Blocker Therapy

• For patients with definite or suspected acute myocardial infarction, metoprolol tartrate should be initiated as soon as the patient's hemodynamic condition has stabilized 3
• Begin with three bolus injections of 5 mg intravenous metoprolol tartrate at approximately 2-minute intervals 3
• In patients who tolerate the full intravenous dose (15 mg), initiate metoprolol tartrate tablets 50 mg every 6 hours, 15 minutes after the last intravenous dose and continue for 48 hours 3
• Thereafter, the maintenance dosage is 100 mg orally twice daily 3

Special Considerations for PCI After Fibrinolytic Therapy

• If PCI is performed ≤24 hours after fibrinolytic therapy: clopidogrel 300 mg loading dose before or at the time of PCI 1
• If PCI is performed >24 hours after fibrinolytic therapy: clopidogrel 600 mg loading dose before or at the time of PCI 1
• If PCI is performed >24 hours after treatment with a fibrin-specific agent or >48 hours after a non-fibrin-specific agent: prasugrel 60 mg at the time of PCI may be reasonable 1

Common Pitfalls and Caveats

• The optimal dose of aspirin remains somewhat controversial, but studies suggest that 162 mg may be as effective as 325 mg with potentially lower bleeding risk 4, 5
• Prasugrel should be avoided in patients with prior stroke or TIA due to increased bleeding risk 1
• When using ticagrelor, the recommended maintenance dose of aspirin is 81 mg daily 1
• Fondaparinux should not be used as the sole anticoagulant during PCI; an additional anticoagulant with anti-IIa activity should be administered 1
• Patients requiring CABG should have clopidogrel or ticagrelor discontinued at least 24 hours before surgery when possible 1
• For long-term secondary prevention, lower doses of aspirin (75-100 mg) appear to have similar efficacy to higher doses with potentially fewer bleeding complications 5, 6