Does Dual Antiplatelet Therapy (DAPT) improve venous graft patency rates after Coronary Artery Bypass Grafting (CABG)?

DAPT and Venous Graft Patency After CABG

Dual antiplatelet therapy (DAPT) with clopidogrel initiated early postoperatively for 12 months after CABG may be reasonable to improve vein graft patency in patients with stable ischemic heart disease (SIHD). 1

Evidence for DAPT in Improving Venous Graft Patency

• The American College of Cardiology/American Heart Association (ACC/AHA) guidelines provide a Class IIb, Level B-NR recommendation for DAPT (with clopidogrel initiated early postoperatively) for 12 months after CABG to improve vein graft patency in patients with SIHD 1
• Meta-analyses have shown mixed but generally favorable results regarding DAPT and vein graft patency:
  • A meta-analysis of 5 RCTs and 6 observational studies demonstrated that DAPT was associated with reduced vein graft occlusion and 30-day mortality compared to aspirin monotherapy 1
  • Another meta-analysis of only RCTs showed significantly lower vein graft occlusion at 1 year with DAPT versus antiplatelet monotherapy 1
• In the only RCT to specifically demonstrate a benefit of DAPT, vein graft patency 3 months after CABG was significantly higher in patients treated with clopidogrel and aspirin (100 mg) than in those receiving aspirin monotherapy 1

DAPT Recommendations Based on Clinical Scenario

• For patients with acute coronary syndrome (ACS) who undergo CABG:
  • P2Y12 inhibitor therapy should be resumed after CABG to complete 12 months of DAPT therapy (Class I, Level C-LD recommendation) 1
  • This recommendation is stronger than for SIHD patients, reflecting the higher thrombotic risk in ACS patients 2
• For patients with SIHD undergoing CABG:
  • DAPT for 12 months after CABG may be reasonable (Class IIb recommendation) 1
  • The evidence is less robust than for ACS patients, but still suggests potential benefit 2

Specific Antiplatelet Recommendations

• When using DAPT, a daily aspirin dose of 81 mg (range, 75 mg to 100 mg) is recommended (Class I, Level B-NR) 1
• Clopidogrel is the default P2Y12 inhibitor when DAPT is indicated after CABG 2
• Recent network meta-analyses suggest that DAPT with low-dose ASA and ticagrelor (OR 2.53,95% CrI 1.35-4.72) or clopidogrel (OR 1.56,95% CrI 1.02-2.39) improved saphenous vein graft patency compared to low-dose ASA monotherapy 3

Bleeding Risk Considerations

• Major bleeding after surgery is more frequent with DAPT compared to aspirin monotherapy 1
• For patients at high bleeding risk, consider a shorter duration of DAPT (6 months) 2
• In patients with increased bleeding risk (e.g., those requiring oral anticoagulation), the benefit/risk ratio may favor shorter-than-recommended duration of DAPT 1

Specific Patient Populations

• Benefits of DAPT in off-pump CABG patients have been noted in terms of improved graft patency in both observational studies and an RCT 1
• For patients who had coronary stent implantation before CABG, P2Y12 inhibitor therapy should be resumed postoperatively so that DAPT continues until the recommended duration of therapy is completed 1

Clinical Algorithm for DAPT After CABG

1. For ACS patients: Resume P2Y12 inhibitor post-operatively and continue for 12 months after the ACS event (Class I recommendation) 1
2. For SIHD patients: Consider DAPT with clopidogrel for 12 months to improve vein graft patency (Class IIb recommendation) 1
3. For patients with high bleeding risk: Consider shorter duration of DAPT (6 months) 2
4. For all patients on DAPT: Use low-dose aspirin (75-100 mg daily) 1

In conclusion, while aspirin monotherapy remains the standard of care after CABG, the evidence suggests that DAPT may improve venous graft patency rates, particularly in the first year after surgery. The decision to use DAPT should consider both the potential benefits for graft patency and the increased risk of bleeding.