Is aspirin alone equivalent to dual antiplatelet therapy (DAPT) with a P2Y12 inhibitor, such as clopidogrel, prasugrel, or ticagrelor, after percutaneous coronary intervention (PCI) in terms of efficacy and safety, particularly with regards to bleeding risk?

Aspirin Alone Is Not Equivalent to DAPT After PCI Due to Increased Ischemic Risk

Based on the most recent and highest quality evidence, aspirin monotherapy is not equivalent to dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI) due to increased risk of major adverse cardiovascular events, particularly stent thrombosis. 1

Current Guideline Recommendations for DAPT After PCI

For Stable Coronary Artery Disease (SCAD)

• DAPT consisting of aspirin 75-100 mg and clopidogrel 75 mg daily for up to 6 months is the standard recommendation after PCI 1
• In patients at high bleeding risk, DAPT can be shortened to 1-3 months 1
• In selected patients, shorter-duration DAPT (1-3 months) with subsequent transition to P2Y12 inhibitor monotherapy (not aspirin alone) is reasonable to reduce bleeding risk 1

For Acute Coronary Syndrome (ACS)

• DAPT is recommended for 12 months as the default strategy 1
• In high bleeding risk patients, DAPT duration can be shortened to 6 months 1
• For patients at high ischemic risk without high bleeding risk, DAPT beyond 12 months may be considered 1

Comparative Efficacy and Safety

Aspirin vs. P2Y12 Inhibitor Monotherapy

Recent evidence suggests that clopidogrel monotherapy may be superior to aspirin monotherapy after completing the initial DAPT period:

• Clopidogrel monotherapy was associated with significant reductions in:

  • Major adverse cardiac events (MACE) (RR 0.77,95% CI 0.65-0.91)
  • Any stroke (RR 0.51,95% CI 0.35-0.76)
  • Ischemic stroke (RR 0.55,95% CI 0.32-0.94)
  • Hemorrhagic stroke (RR 0.24,95% CI 0.09-0.68) 2

• No significant differences were found in:

  • Cardiac death, all-cause death, major bleeding, MI, repeat revascularization, or stent thrombosis 2

P2Y12 Inhibitor Monotherapy vs. DAPT

The TWILIGHT trial demonstrated that after 3 months of DAPT, ticagrelor monotherapy compared to continued DAPT (ticagrelor plus aspirin) resulted in:

• Lower incidence of clinically relevant bleeding (4.0% vs. 7.1%; HR 0.56,95% CI 0.45-0.68)
• No increase in ischemic events (3.9% in both groups) 3

Optimal Approach to Antiplatelet Therapy After PCI

Initial DAPT Period

1. All patients should receive DAPT initially after PCI:
   • SCAD: 1-6 months of DAPT (aspirin + clopidogrel)
   • ACS: 12 months of DAPT (aspirin + ticagrelor/prasugrel preferred over clopidogrel)

After Initial DAPT Period

1. Transition options after completing the required DAPT duration:
   • Preferred option: P2Y12 inhibitor monotherapy (particularly clopidogrel or ticagrelor)
   • Alternative: Aspirin monotherapy (traditional approach but may be less effective than P2Y12 inhibitor monotherapy)

Special Considerations

1. For patients requiring oral anticoagulation:
   • Triple therapy (DAPT + anticoagulant) increases bleeding risk 2-3 fold 1
   • Aspirin should be discontinued after 1-4 weeks, continuing P2Y12 inhibitor (preferably clopidogrel) plus anticoagulant 1

Clinical Pitfalls and Caveats

• Premature DAPT discontinuation: Stopping DAPT too early increases risk of stent thrombosis, MI, and death 4
• Bleeding risk assessment: Use validated tools (e.g., PRECISE-DAPT score) to identify high bleeding risk patients who may benefit from shorter DAPT 4
• Drug interactions: Proton pump inhibitors may reduce clopidogrel's effectiveness; this interaction is less significant with newer P2Y12 inhibitors 1
• Compliance concerns: P2Y12 inhibitors like ticagrelor require twice-daily dosing, which may affect adherence compared to once-daily aspirin 4

In conclusion, while aspirin monotherapy has been the traditional approach after completing DAPT, current evidence suggests it is not equivalent to DAPT in terms of efficacy. When DAPT must be discontinued, P2Y12 inhibitor monotherapy appears to be a more effective alternative than aspirin alone, with a similar or potentially better safety profile.