What is the recommended antiplatelet therapy after 12 months in patients with a history of myocardial infarction (MI)?

Antiplatelet Therapy After 12 Months in Patients with History of Myocardial Infarction

For patients with a history of myocardial infarction (MI), continuation of dual antiplatelet therapy (DAPT) beyond 12 months may be reasonable in those who have tolerated DAPT without bleeding complications and who are not at high bleeding risk. 1

Standard Recommendations After 12 Months

After completing the initial 12-month DAPT course following MI, the recommended antiplatelet therapy depends on several factors:

For Most Post-MI Patients:

• Aspirin monotherapy: Continue aspirin 75-100 mg daily lifelong 1
• This is a Class I, Level A recommendation for secondary prevention 1

For Extended DAPT Consideration:

• Patients who may benefit from DAPT continuation beyond 12 months:
  • Those who have tolerated DAPT without bleeding complications
  • Those without high bleeding risk factors (prior bleeding on DAPT, coagulopathy, oral anticoagulant use) 1
  • Patients with high ischemic risk features

P2Y12 Inhibitor Options for Extended Therapy

If extending DAPT beyond 12 months is considered appropriate:

• Ticagrelor 60 mg twice daily is preferred for extended therapy in patients with prior MI (Class IIb, Level B) 1
• Clopidogrel 75 mg daily is an alternative option (Class IIb, Level C) 1
• Prasugrel is not recommended for extended therapy beyond 12 months 1
• Prasugrel should never be used in patients with prior history of stroke or TIA (Class III: Harm, Level B-R) 1

Risk Assessment for DAPT Duration Decision

High Bleeding Risk Factors (favor shorter DAPT or aspirin monotherapy):

• Advanced age (≥65 years)
• History of bleeding
• Oral anticoagulant use
• Low body weight
• Chronic kidney disease
• Coagulopathy 2, 3

High Ischemic Risk Factors (favor extended DAPT):

• Complex coronary anatomy
• Prior stent thrombosis
• Multiple prior MIs
• Diabetes mellitus
• Peripheral arterial disease 2, 4

Special Considerations

For Patients with Atrial Fibrillation:

• After 12 months post-MI, discontinuation of antiplatelet therapy is recommended in patients treated with an oral anticoagulant (OAC) 1
• Prior to 12 months, a dual antithrombotic therapy (DAT) approach with OAC plus a single antiplatelet agent (preferably clopidogrel) is recommended 1

For Patients with High Ischemic Risk:

• Extended DAPT (18-48 months) compared to 6-12 months shows:
  • Decreased MI (OR: 0.67; 95% CI: 0.47 to 0.95)
  • Decreased stent thrombosis (OR: 0.45; 95% CI: 0.24 to 0.74)
  • But increased major hemorrhage (OR: 1.58; 95% CI: 1.20 to 2.09) 2

Common Pitfalls to Avoid

1. Premature discontinuation of DAPT: Increases risk of stent thrombosis, MI, and death, especially in the first year 2

2. Not considering bleeding risk: Bleeding events can significantly impact morbidity, mortality, and quality of life

3. Failure to reassess risk periodically: Both ischemic and bleeding risks may change over time

4. Complete discontinuation of all antiplatelet therapy: Significantly increases cardiovascular risk in post-MI patients 2

5. Not accounting for drug interactions: Certain medications can affect P2Y12 inhibitor metabolism or increase bleeding risk 2

Summary Algorithm for Post-12 Month Antiplatelet Therapy

1. Assess bleeding risk:

   • If high bleeding risk → Aspirin monotherapy
   • If low-moderate bleeding risk → Continue to step 2

2. Assess ischemic risk:

   • If high ischemic risk → Consider extended DAPT
   • If low-moderate ischemic risk → Aspirin monotherapy

3. If extended DAPT chosen:

   • First choice: Aspirin + ticagrelor 60mg BID
   • Alternative: Aspirin + clopidogrel 75mg daily
   • Avoid prasugrel for extended therapy

4. Reassess regularly for changes in bleeding or ischemic risk

Remember that while the traditional recommendation has been 12 months of DAPT after MI, recent evidence suggests that individualized approaches based on bleeding and ischemic risk may provide better outcomes 5.