What is the recommended Dual Antiplatelet Therapy (DAPT) regimen for a patient post-Myocardial Infarction (MI) after being on blood thinners for a year?

DAPT After Post-MI: Transition to Aspirin Monotherapy at 12 Months

After completing 12 months of dual antiplatelet therapy (DAPT) following myocardial infarction, transition to lifelong aspirin monotherapy at 75-100 mg daily is the standard recommendation for most patients. 1, 2

Standard Post-MI DAPT Duration

• All post-MI patients should receive DAPT (aspirin plus a P2Y12 inhibitor) for a minimum of 12 months, regardless of whether they underwent PCI with stenting, received fibrinolytic therapy, or were managed medically. 1, 3, 4

• The P2Y12 inhibitor options include clopidogrel 75 mg daily, ticagrelor 90 mg twice daily, or prasugrel 10 mg daily (5 mg if weight <60 kg or age ≥75 years). 1, 3

• Ticagrelor is preferred over clopidogrel for maintenance therapy after ACS, with a Class IIa recommendation from ACC/AHA and Class I recommendation from ESC. 1

• Prasugrel should never be used in patients with prior stroke or TIA due to increased cerebrovascular bleeding risk (6.5% vs 1.2% with clopidogrel). 1, 3, 5

• Aspirin dosing during and after DAPT should be 75-100 mg daily (typically 81 mg in the US). 1, 2, 3

After 12 Months: Standard Approach

• Transition to lifelong single antiplatelet therapy (SAPT) with aspirin 75-100 mg daily is the Class I, Level A recommendation for secondary prevention after completing the initial DAPT period. 2

• Clopidogrel 75 mg daily is an equally effective alternative to aspirin for lifelong monotherapy and can be substituted based on tolerability or side effects. 2

• Discontinuing all antiplatelet therapy after completing DAPT is a dangerous error that significantly increases thrombotic risk. 2

Extended DAPT Beyond 12 Months: Who Qualifies?

Extended DAPT (beyond 12 months up to 36 months) may be reasonable in highly selected post-MI patients who meet ALL of the following criteria: 1

• Tolerated the initial 12 months of DAPT without any bleeding complications 1, 3

• Not at high bleeding risk, defined as absence of: 1, 3

  • Prior bleeding on DAPT
  • Coagulopathy
  • Oral anticoagulant use
  • Age >75 years (relative)
  • Low body weight <60 kg (relative)
  • Chronic kidney disease requiring dialysis (relative)

• High ischemic risk features such as: 1

  • Diabetes mellitus
  • Recurrent MI
  • Multivessel coronary disease
  • Chronic kidney disease (not on dialysis)
  • Prior stent thrombosis

Evidence for Extended DAPT

• The PEGASUS-TIMI 54 trial demonstrated that ticagrelor 60 mg twice daily (reduced dose) plus aspirin in post-MI patients (1-3 years after MI) reduced cardiovascular death, MI, or stroke by 1.2-1.3% absolute risk but increased major bleeding by 1.2-1.5% absolute risk. 1

• The greatest benefit occurred when P2Y12 inhibitor therapy had not been discontinued or was discontinued ≤30 days before enrollment (absolute MACE reduction: 1.9-2.5%). 1, 4

• No benefit was observed in patients who had discontinued P2Y12 therapy >1 year before attempting to restart extended DAPT. 1

Specific Regimen for Extended DAPT

If extended DAPT is chosen based on the above criteria: 1

• Ticagrelor 60 mg twice daily plus aspirin 75-100 mg daily (Class IIb, Level B recommendation from both ACC/AHA and ESC) 1

• Clopidogrel 75 mg daily plus aspirin is an alternative but with weaker evidence (Class IIb, Level C from ESC). 1

• Prasugrel is NOT recommended for extended DAPT beyond 12 months (Class III recommendation from ESC). 1

• Alternative: Rivaroxaban 2.5 mg twice daily plus aspirin may be considered in high ischemic risk patients (NNT=77, NNH=84 from COMPASS trial). 1

Shortened DAPT Duration: High Bleeding Risk Patients

• In post-MI patients who develop high bleeding risk or significant bleeding, discontinuation of the P2Y12 inhibitor after 6 months may be reasonable (Class IIa, Level C), transitioning to aspirin monotherapy. 1, 3

• High bleeding risk is defined as 1-year risk of serious bleeding ≥4% or intracranial hemorrhage risk ≥1%. 5

Critical Pitfalls to Avoid

• Never discontinue all antiplatelet therapy after completing DAPT—this is the most dangerous error. 2

• Do not extend DAPT beyond 12 months without reassessing bleeding and ischemic risk, as bleeding risk increases by approximately 1% absolute without clear benefit in low-risk patients. 2, 4

• Do not restart extended DAPT if the patient has already been off P2Y12 inhibitors for >1 year, as no benefit was demonstrated in this scenario. 1

• Avoid aspirin doses >100 mg daily during or after DAPT, as higher doses increase bleeding without improving efficacy. 1, 4

• Never use prasugrel in patients with prior stroke/TIA at any timepoint. 1, 3, 4, 5

Algorithm for Decision-Making at 12 Months Post-MI

Step 1: Assess bleeding complications during initial 12 months of DAPT

• If bleeding occurred → Stop P2Y12 inhibitor, continue aspirin monotherapy lifelong 1
• If no bleeding → Proceed to Step 2

Step 2: Assess current bleeding risk factors

• If high bleeding risk present (oral anticoagulation, coagulopathy, prior bleeding, age >75, weight <60 kg) → Stop P2Y12 inhibitor, continue aspirin monotherapy lifelong 1
• If low bleeding risk → Proceed to Step 3

Step 3: Assess ischemic risk factors

• If ≥2 high ischemic risk features present (diabetes, recurrent MI, multivessel disease, CKD) → Consider extended DAPT with ticagrelor 60 mg BID + aspirin for up to 36 months 1
• If <2 high ischemic risk features → Stop P2Y12 inhibitor, continue aspirin monotherapy lifelong 1, 2

Step 4: If extended DAPT chosen, reassess bleeding and ischemic risk every 6-12 months 1