What is DAPT (Dual Antiplatelet Therapy) in Ischemic Heart Disease (IHD)?

Dual Antiplatelet Therapy (DAPT) in Ischemic Heart Disease (IHD)

Dual antiplatelet therapy (DAPT) in ischemic heart disease (IHD) consists of aspirin plus a P2Y12 inhibitor (clopidogrel, ticagrelor, or prasugrel) and is primarily recommended for patients following acute coronary syndrome (ACS) or percutaneous coronary intervention (PCI) to prevent thrombotic events.

Definition and Components of DAPT

• DAPT refers to the combination of aspirin and a P2Y12 inhibitor (clopidogrel, prasugrel, or ticagrelor) 1
• Aspirin is typically given at a daily dose of 81 mg (range 75-100 mg) for optimal efficacy with reduced bleeding risk 1
• P2Y12 inhibitors prevent platelet activation through a different mechanism than aspirin, providing complementary antiplatelet effects 1

DAPT Duration Based on Clinical Scenario

After PCI with Drug-Eluting Stent (DES)

• For stable ischemic heart disease (SIHD): DAPT recommended for at least 6 months 1
• For acute coronary syndrome (ACS): DAPT recommended for at least 12 months 1
• For high bleeding risk patients with SIHD: P2Y12 inhibitor may be discontinued after 3 months if necessary 1
• Extended DAPT beyond 12 months may be reasonable in selected patients at low bleeding risk and high ischemic risk 1

After Coronary Artery Bypass Grafting (CABG)

• DAPT with clopidogrel for 12 months after CABG may be reasonable to improve vein graft patency 1
• However, evidence for routine DAPT use post-CABG in SIHD patients is limited, with studies showing no significant difference in outcomes compared to aspirin monotherapy 2

Medically Managed ACS

• For ACS patients managed with medical therapy alone (without revascularization), DAPT with clopidogrel or ticagrelor should be continued for at least 12 months 1

Stable IHD Without Recent Intervention

• In patients with SIHD without prior history of ACS, coronary stent implantation, or recent CABG (within 12 months), DAPT is not beneficial and is not recommended 1, 3

Benefits and Risks of Extended DAPT

Benefits of Extended DAPT

• In the DAPT study, extending therapy from 12 to 30 months after DES implantation resulted in 1:
  • 0.7% absolute reduction in very late stent thrombosis
  • 2.0% absolute reduction in myocardial infarction
  • 1.6% absolute reduction in major adverse cardiac events (MACE)

Risks of Extended DAPT

• Extended DAPT increases bleeding risk by approximately 1% 1
• In the DAPT study, 30 months vs. 12 months of DAPT resulted in 1:
  • 0.9% absolute increase in moderate or severe bleeding
  • A borderline-significant increase in overall mortality (0.5% absolute increase)
• Risk-benefit analysis found 6 fewer MIs and 3 fewer stent thromboses but 5 additional major bleeds per 1000 patients treated with prolonged DAPT per year 1

Risk Assessment for DAPT Duration

• The decision regarding DAPT duration should be dynamic and reassessed during treatment 1
• Consider both ischemic and bleeding risk factors when determining optimal DAPT duration 1
• For patients at high bleeding risk who develop significant bleeding complications, discontinuation of P2Y12 inhibitor after 3 months may be reasonable if DES was used 1

Special Considerations

Patients Requiring Anticoagulation

• For patients requiring oral anticoagulation who undergo PCI, triple therapy (DAPT plus anticoagulant) increases bleeding risk significantly 1
• Consider shorter durations of triple therapy followed by dual therapy (anticoagulant plus single antiplatelet) when bleeding risk outweighs ischemic risk 1

Perioperative Management

• For elective surgery requiring discontinuation of P2Y12 inhibitor, ticagrelor should be interrupted 3 days prior to surgery 1
• For patients with recent stent placement (within 1 month), elective procedures should be deferred when possible 4
• Never discontinue both antiplatelet agents simultaneously due to high risk of stent thrombosis 4

Common Pitfalls and Caveats

• Premature discontinuation risk: Stopping DAPT prematurely increases the risk of stent thrombosis, particularly within the first 3 months after DES implantation 1
• Bleeding risk management: Consider proton pump inhibitors to mitigate gastrointestinal bleeding risk in patients on DAPT 1
• Balance of risks: The decision to extend DAPT beyond recommended durations must carefully weigh reduced ischemic events against increased bleeding risk 1
• Newer-generation DES: Modern DES have lower stent thrombosis rates than first-generation DES, which may influence the risk-benefit ratio of extended DAPT 1

In summary, DAPT is a cornerstone therapy for patients with IHD following ACS or coronary intervention, with duration tailored based on clinical presentation, intervention type, and individual risk factors for both ischemic and bleeding events.