How long should dual antiplatelet therapy (DAPT) be continued after stent placement in a patient with acute myocardial infarction (AMI)?

Duration of Dual Antiplatelet Therapy After Stent in Acute Myocardial Infarction

In patients with acute myocardial infarction (AMI) treated with coronary stent implantation, dual antiplatelet therapy (DAPT) should be continued for at least 12 months. 1

Standard DAPT Duration for AMI Patients

• P2Y12 inhibitor therapy (clopidogrel, prasugrel, or ticagrelor) combined with aspirin should be given for at least 12 months after stent implantation in AMI patients, regardless of whether a bare metal stent (BMS) or drug-eluting stent (DES) was used 1
• A daily aspirin dose of 81 mg (range 75-100 mg) is recommended as part of DAPT 1
• For patients with AMI treated with medical therapy alone (without revascularization) or with fibrinolytic therapy, DAPT should also be continued for at least 12 months 1

Choice of P2Y12 Inhibitor

• In AMI patients treated with stent implantation, it is reasonable to use ticagrelor in preference to clopidogrel for maintenance P2Y12 inhibitor therapy 1
• For patients without high bleeding risk and without history of stroke or TIA, prasugrel is a reasonable choice over clopidogrel 1
• Prasugrel should not be administered to patients with prior history of stroke or TIA due to increased bleeding risk 1

Special Considerations for DAPT Duration

Extended DAPT (>12 months)

• In AMI patients who have tolerated DAPT without bleeding complications and who are not at high bleeding risk (e.g., prior bleeding on DAPT, coagulopathy, oral anticoagulant use), continuation of DAPT beyond 12 months may be reasonable 1
• Extended DAPT reduces the risk of stent thrombosis and myocardial infarction but increases the risk of bleeding 2
• The DAPT trial showed that continued thienopyridine treatment beyond 12 months reduced rates of stent thrombosis (0.4% vs 1.4%) and major adverse cardiovascular events (4.3% vs 5.9%) compared to placebo, but increased bleeding risk (2.5% vs 1.6%) 2

Shortened DAPT (<12 months)

• In AMI patients treated with DES who develop high bleeding risk (e.g., need for oral anticoagulant therapy), are at high risk of severe bleeding complications, or develop significant overt bleeding, discontinuation of P2Y12 therapy after 6 months may be reasonable 1
• Recent research suggests that 6-month DAPT followed by aspirin alone results in comparable net adverse clinical events compared to ≥12-month DAPT in patients with MI who are event-free at six months after DES implantation 3
• However, shortened DAPT (6 months) was associated with higher rates of MI compared to ≥12-month DAPT (1.6% vs 0.6%) 3

DAPT After CABG in AMI Patients

• In AMI patients being treated with DAPT who undergo coronary artery bypass grafting (CABG), P2Y12 inhibitor therapy should be resumed after CABG to complete 12 months of DAPT therapy after the AMI 1
• Before CABG, P2Y12 inhibitors should be discontinued to decrease perioperative bleeding risk (at least 3 days for ticagrelor, 5 days for clopidogrel, and 7 days for prasugrel) 1

Risk-Benefit Assessment

• The decision regarding DAPT duration requires balancing thrombotic and bleeding risks 1
• Extended DAPT (>12 months) reduces ischemic events but increases bleeding risk 1, 2
• Shortened DAPT (<12 months) reduces bleeding risk but may increase ischemic events, particularly MI 3
• Recent network meta-analysis suggests that short-term DAPT followed by P2Y12 inhibitor monotherapy reduces major bleeding after PCI with drug-eluting stents compared to 12-month DAPT, while extended-term DAPT reduces myocardial infarction at the expense of more bleeding events 4

Common Pitfalls to Avoid

• Failing to consider both bleeding and ischemic risks when determining DAPT duration 1
• Prematurely discontinuing DAPT within the first 12 months after AMI without compelling reasons 1
• Using prasugrel in patients with history of stroke or TIA 1
• Not adjusting aspirin dose to the recommended 75-100 mg daily when used as part of DAPT 1
• Discontinuing DAPT without considering the type of stent used and the timing of stent implantation 1, 5

In conclusion, the standard recommendation for DAPT duration after stent placement in AMI is at least 12 months, with potential extension beyond 12 months in patients at low bleeding risk and potential shortening to 6 months in patients at high bleeding risk.