What is the recommended anticoagulant and antiplatelet therapy regimen, including duration of treatment, for a patient following an acute myocardial infarction (MI)?

Anticoagulant and Antiplatelet Therapy Following Acute MI

All patients with acute MI should receive dual antiplatelet therapy (DAPT) consisting of aspirin 81 mg daily plus a P2Y12 inhibitor for at least 12 months as the default strategy, with ticagrelor or prasugrel strongly preferred over clopidogrel in patients undergoing PCI. 1

Initial Antiplatelet Regimen

Choice of P2Y12 Inhibitor

For ACS patients undergoing PCI:

• Ticagrelor or prasugrel is recommended in preference to clopidogrel 1
• Ticagrelor is reasonable to use in preference to clopidogrel for maintenance therapy 1
• Prasugrel is reasonable over clopidogrel in patients without history of stroke/TIA and not at high bleeding risk 1
• Prasugrel is contraindicated in patients with prior stroke or TIA (6.5% stroke rate vs 1.2% with clopidogrel) 2
• Prasugrel is generally not recommended in patients ≥75 years due to increased fatal and intracranial bleeding risk, except in high-risk situations (diabetes or prior MI) 2

For ACS managed medically (no revascularization):

• P2Y12 inhibitor (clopidogrel or ticagrelor) should be continued for at least 12 months 1
• Ticagrelor is reasonable in preference to clopidogrel for NSTE-ACS 1

For STEMI treated with fibrinolytic therapy:

• Clopidogrel should be continued for minimum 14 days and ideally at least 12 months 1, 3
• Clopidogrel loading dose of 300 mg is reasonable for patients <75 years 3

Aspirin Dosing

• Daily aspirin dose of 81 mg (range 75-100 mg) is recommended in all patients on DAPT 1

Duration of DAPT

Standard Duration (12 Months)

• At least 12 months of DAPT is the default strategy for all ACS patients (whether treated with PCI, medical therapy alone, or fibrinolysis) who are not at high bleeding risk 1

Shortened Duration (3-6 Months)

Consider shorter DAPT duration in high bleeding risk patients:

• Patients with prior bleeding on DAPT 1
• Coagulopathy present 1
• Concurrent oral anticoagulant use 1
• Age ≥65 years, low body weight (BMI <18.5), diabetes 4
• Discontinuation of P2Y12 inhibitor after 6 months may be reasonable in ACS patients with high bleeding risk 1

Extended Duration (>12 Months)

May be reasonable in select patients who:

• Have tolerated DAPT without bleeding complications 1
• Are not at high bleeding risk 1
• Have high ischemic risk 1
• Note: Extended DAPT reduces MI and stent thrombosis but increases bleeding risk 5, 6

Mandatory Anticoagulation During Acute Phase

For STEMI patients receiving fibrinolytic therapy:

• Anticoagulation is mandatory in all patients until revascularization or for hospital duration up to 8 days 3
• Enoxaparin is preferred over unfractionated heparin (UFH) 3
• UFH: weight-adjusted IV bolus followed by infusion 3
• Fondaparinux is reasonable for patients treated with streptokinase 3
• Avoid fondaparinux as sole anticoagulation during PCI (increases catheter thrombosis risk; requires additional UFH or bivalirudin) 3

Bleeding Risk Mitigation Strategies

Three evidence-based approaches to reduce bleeding in ACS patients post-PCI:

1. Proton pump inhibitor (PPI) is recommended in patients at risk for gastrointestinal bleeding 1

2. Transition to ticagrelor monotherapy (discontinue aspirin) is recommended ≥1 month after PCI in patients who have tolerated DAPT with ticagrelor 1

3. Aspirin discontinuation 1-4 weeks post-PCI with continued P2Y12 inhibitor (preferably clopidogrel) in patients requiring long-term anticoagulation 1

Special Populations

Low Body Weight (<60 kg)

• Consider lowering prasugrel maintenance dose to 5 mg daily (from standard 10 mg) due to increased bleeding risk 2

Patients Requiring Oral Anticoagulation (Triple Therapy)

• Aspirin should be discontinued 1-4 weeks after PCI, continuing with oral anticoagulant plus P2Y12 inhibitor (preferably clopidogrel) 1
• Keep triple therapy duration as short as possible 1
• Target INR 2.0-2.5 when warfarin is used 1
• Clopidogrel is the P2Y12 inhibitor of choice in this setting 1

Critical Pitfalls to Avoid

• Never discontinue DAPT abruptly in the first few weeks after ACS, as this substantially increases risk of subsequent cardiovascular events 2
• Do not use prasugrel in patients with prior stroke/TIA (contraindicated) 1, 2
• Avoid prasugrel in patients ≥75 years unless high-risk features present (diabetes, prior MI) 2
• Do not start prasugrel in patients likely to undergo urgent CABG; discontinue at least 7 days prior to surgery when possible 2
• Recognize that newer P2Y12 inhibitors (prasugrel, ticagrelor) act within 30 minutes vs 2 hours for clopidogrel, with significantly lower residual platelet reactivity (3% vs 30-40%) 4