What is the need for dual antiplatelet therapy (DAPT) in patients with myocardial infarction (MI)?

Dual Antiplatelet Therapy After Myocardial Infarction

All patients with myocardial infarction require dual antiplatelet therapy (aspirin plus a P2Y12 inhibitor) for at least 12 months, regardless of whether they undergo PCI, CABG, or receive medical management alone. 1

Core Rationale for DAPT in MI

DAPT is essential after MI because it addresses two distinct mechanisms of thrombosis:

• Aspirin inhibits thromboxane A2-mediated platelet aggregation through irreversible COX-1 inhibition 2
• P2Y12 inhibitors (clopidogrel, prasugrel, or ticagrelor) block ADP-mediated platelet activation, providing complementary antiplatelet coverage 2

The combination reduces major adverse cardiovascular events (MACE) including recurrent MI, stent thrombosis, cardiovascular death, and stroke compared to aspirin monotherapy 3, 4

Standard DAPT Duration After MI

Minimum Duration: 12 Months

For all ACS patients (STEMI and NSTEMI), the default DAPT duration is 12 months regardless of management strategy (medical therapy alone, PCI with stenting, or CABG). 1, 3

This recommendation applies to:

• STEMI patients treated with primary PCI, fibrinolytic therapy, or medical management alone 3
• NSTEMI/unstable angina patients managed with PCI or conservatively 3
• Post-CABG MI patients who should resume P2Y12 inhibitor therapy postoperatively to complete 12 months total DAPT 3

P2Y12 Inhibitor Selection

For ACS patients undergoing PCI, ticagrelor (180 mg loading, 90 mg twice daily) or prasugrel (60 mg loading, 10 mg daily) are preferred over clopidogrel due to superior efficacy in reducing cardiovascular events. 1, 2

• Prasugrel is contraindicated in patients with prior stroke/TIA (increased ICH risk: 6.5% vs 1.2% with clopidogrel), age ≥75 years (unless high-risk diabetes or prior MI), or weight <60 kg (consider 5 mg dose) 5
• Ticagrelor has no stroke contraindication and demonstrated superiority over clopidogrel in the PLATO trial 3
• Clopidogrel (300-600 mg loading, 75 mg daily) is the default choice when ticagrelor or prasugrel are contraindicated or when oral anticoagulation is required 3, 1

STEMI-Specific Considerations

For STEMI patients receiving fibrinolytic therapy:

• Minimum 14 days of DAPT is required, with aspirin plus clopidogrel recommended based on CLARITY-TIMI 28 and COMMIT trials 3
• Ideally extend to 12 months following the same rationale as for PCI-treated STEMI 3

Extended DAPT Beyond 12 Months

When to Consider Prolonged DAPT (18-36 months)

For post-MI patients who complete 12 months of DAPT without bleeding complications and are not at high bleeding risk, continuation beyond 12 months may be reasonable. 3, 1

The decision requires weighing:

• Ischemic benefit: Absolute reduction in MACE of 1-3% 3
• Bleeding risk: Absolute increase in major bleeding of ≥1% 3

Greatest benefit occurs when P2Y12 inhibitor has not been discontinued or was discontinued ≤30 days (absolute MACE reduction: 1.9-2.5%). No benefit when discontinued >1 year before. 3

High-Risk Features Favoring Extended DAPT

Consider prolonged DAPT (>12 months) in patients with: 3

• Prior stent thrombosis without correctable causes (e.g., non-adherence, mechanical stent issues) 3, 1
• Complex PCI: ≥3 stents implanted, ≥3 lesions treated, bifurcation with 2 stents, total stent length >60 mm, or chronic total occlusion 3
• Peripheral arterial disease with coronary artery disease 3
• Diabetes mellitus with prior MI in patients ≥75 years on prasugrel 5

Shortened DAPT Duration (3-6 Months)

High Bleeding Risk Patients

For patients at high bleeding risk, shortened DAPT to 6 months should be considered while continuing aspirin monotherapy thereafter. 1, 3

High bleeding risk is defined as:

• ≥4% annual risk of serious bleeding (fatal or ≥3 g/dL hemoglobin drop) or ≥1% risk of intracranial hemorrhage 2
• Clinical features: Age ≥65 years, BMI <18.5, diabetes, prior bleeding, oral anticoagulation requirement, weight <60 kg 2, 5
• PRECISE-DAPT score ≥25 3

Mandatory Early Discontinuation Scenarios

Discontinue P2Y12 inhibitor (continue aspirin) immediately if: 3

• Significant overt bleeding occurs that cannot be managed without stopping DAPT
• Life-threatening bleeding where the source cannot be treated 3
• Patient develops stroke/TIA while on prasugrel (prasugrel contraindication) 5

Never discontinue both antiplatelet agents simultaneously except in life-threatening bleeding situations, as this dramatically increases stent thrombosis risk. 3, 6

Special Populations

Patients Requiring Oral Anticoagulation

Triple therapy (DAPT plus oral anticoagulation) increases bleeding risk 2-3 fold and should be limited to maximum 6 months or omitted after hospital discharge. 1, 3

• Prefer NOACs over warfarin due to favorable bleeding profile 3
• Use clopidogrel as the P2Y12 inhibitor (not ticagrelor or prasugrel) 1
• Minimize triple therapy duration based on bleeding and ischemic risk assessment 3

MINOCA (MI with Non-Obstructive CAD)

Patients with MINOCA have lower recurrent event rates (CV mortality 0.6% vs 2.2%, repeat MI 0.5% vs 2.3%) compared to obstructive CAD. 7

Intensified DAPT dosing (double-dose clopidogrel) showed possible harm in MINOCA (primary outcome 2.1% vs 0.6% with standard dose, HR 3.57), suggesting standard-dose DAPT is appropriate. 7

Perioperative Management

Elective Non-Cardiac Surgery Timing

Delay elective surgery until: 3

• 30 days after bare metal stent implantation (Class I recommendation)
• Optimally 6 months after drug-eluting stent implantation (Class I recommendation)
• Minimum 3 months after DES may be considered if surgery delay risk exceeds stent thrombosis risk (Class IIb)

P2Y12 Inhibitor Discontinuation Before Surgery

When surgery cannot be delayed and P2Y12 inhibitor must be stopped: 3

• Clopidogrel: Discontinue ≥5 days before surgery
• Ticagrelor: Discontinue ≥3 days before surgery
• Prasugrel: Discontinue ≥7 days before surgery

Continue aspirin throughout the perioperative period whenever possible (Class I recommendation). 3, 6

Resume P2Y12 inhibitor as soon as adequate hemostasis is achieved to complete the recommended DAPT duration. 3, 6

Post-CABG Management

Resume P2Y12 inhibitor postoperatively as soon as deemed safe to complete the full 12-month DAPT course in MI patients. 3

For CABG patients with prior MI at high bleeding risk (PRECISE-DAPT ≥25), discontinuation after 6 months should be considered. 3

Critical Reassessment Timepoints

Mandatory reassessment at 12 months for all patients to actively decide continuation versus discontinuation of DAPT. 1

Immediate reassessment required if: 1

• Significant bleeding occurs on DAPT
• Major surgery (especially intracranial) is planned
• Patient develops stroke/TIA on prasugrel
• New indication for oral anticoagulation arises

Failure to reassess at 12 months is a critical error - the decision must be actively made, not passively continued. 1

Common Pitfalls to Avoid

• Never discontinue both antiplatelet agents simultaneously - maintain aspirin if P2Y12 inhibitor must be stopped 3, 6
• Do not use prasugrel in patients with prior stroke/TIA - 6.5% stroke rate vs 1.2% with clopidogrel 5
• Do not delay resumption of P2Y12 inhibitor after surgery once hemostasis is adequate 6
• Do not use standard-dose prasugrel (10 mg) in patients <60 kg - consider 5 mg dose due to increased bleeding 5
• Do not extend triple therapy beyond 6 months in patients requiring anticoagulation 1, 3