What is the recommended aspirin (acetylsalicylic acid) regimen after Coronary Artery Bypass Grafting (CABG)?

Aspirin Regimen After Coronary Artery Bypass Grafting (CABG)

Aspirin at a dose of 100-325 mg should be initiated within 6 hours after CABG surgery and continued indefinitely to improve saphenous vein graft patency and reduce mortality. 1

Initial Dosing and Timing

• If not started preoperatively, aspirin should be initiated within 6 hours postoperatively 1
• Dosing options:
  • 100-325 mg daily is the recommended range 1
  • Higher doses (325 mg) may provide better suppression of thromboxane and lower incidence of residual platelet activity in the early post-CABG period 2
  • 81 mg daily is commonly used in practice and considered acceptable by the ACC/AHA 1

Long-term Aspirin Therapy

• Continue aspirin indefinitely after CABG 1
• For long-term maintenance:
  • 75-162 mg daily is recommended for indefinite use 1
  • Non-enteric coated formulations may be preferred, as enteric-coated aspirin has been associated with suboptimal platelet inhibition in some patients 1

Special Considerations

Dual Antiplatelet Therapy (DAPT)

• For patients with acute coronary syndrome (ACS) prior to CABG:

  • Continue clopidogrel 75 mg daily in combination with aspirin for up to 12 months 1

• For patients with stent placement prior to CABG:

  • Higher-dose aspirin (325 mg daily) for:
    • 1 month for bare metal stent
    • 3 months for sirolimus-eluting stent
    • 6 months for paclitaxel-eluting stent 1

• For patients undergoing CABG without prior ACS or stent:

  • Adding clopidogrel to aspirin may be reasonable to improve vein graft patency, particularly for radial artery grafts 3, 4
  • However, evidence for routine DAPT in stable CAD patients after CABG is insufficient for a strong recommendation 3

Aspirin Alternatives

• For patients intolerant or allergic to aspirin:
  • Clopidogrel 75 mg daily is a reasonable alternative 1

Clinical Benefits

• Early postoperative aspirin (within 48 hours) has been shown to:
  • Improve saphenous vein graft patency rates, particularly in the first postoperative year 1, 5
  • Reduce rates of mortality, MI, stroke, renal failure, and bowel infarction 1
  • Provide continued protection against graft occlusion up to 1 year after CABG 5

Common Pitfalls and Caveats

1. Delayed initiation: Benefit of aspirin on graft patency is lost if initiated more than 48 hours after surgery 1

2. Dose considerations:

   • While 81 mg is commonly used, higher doses (100-325 mg) may provide better suppression of platelet function early after CABG 2, 6
   • Enteric-coated low-dose aspirin may provide suboptimal platelet inhibition in up to 44% of patients 1

3. Bleeding concerns:

   • Despite concerns, studies show that early postoperative aspirin does not significantly increase bleeding compared to placebo 5
   • Blood loss and transfusion requirements are similar between aspirin and placebo groups 5

4. Arterial vs. venous grafts:

   • Aspirin significantly improves saphenous vein graft patency
   • Arterial graft patency rates are high even without antiplatelet therapy 1

In summary, aspirin therapy should be initiated within 6 hours after CABG at a dose between 100-325 mg daily and continued indefinitely. For long-term maintenance, doses of 75-162 mg daily are appropriate. Higher doses may be more effective in the early postoperative period, while lower doses are sufficient for long-term therapy.