What is the recommended antiplatelet therapy for patients after Coronary Artery Bypass Grafting (CABG)?

Antiplatelet Therapy After CABG

All patients undergoing CABG should receive aspirin 75-100 mg daily started within 6-24 hours postoperatively and continued indefinitely, with the addition of a P2Y12 inhibitor (clopidogrel, prasugrel, or ticagrelor) resumed postoperatively to complete 12 months of dual antiplatelet therapy (DAPT) if the patient had a recent acute coronary syndrome or prior coronary stent. 1

Core Recommendations by Clinical Scenario

For Patients with Recent ACS (NSTE-ACS or STEMI)

• Resume P2Y12 inhibitor therapy postoperatively to complete 12 months of DAPT after the ACS event (Class I, Level C-LD recommendation) 1
• This applies regardless of whether the patient underwent PCI before CABG 1
• The mortality benefit was demonstrated in post-hoc analyses, with prasugrel showing significantly lower 30-day mortality compared to clopidogrel, and ticagrelor demonstrating significant reduction in cardiovascular mortality 1

For Patients with Prior Coronary Stents

• P2Y12 inhibitor therapy should be resumed postoperatively to continue until the recommended duration for the stent type is completed (Class I, Level C-EO) 1
• Minimum 1 month for bare metal stents 1
• At least 6 months for drug-eluting stents 1

For Patients with Stable Ischemic Heart Disease (SIHD) Without Recent ACS

• DAPT with clopidogrel 75 mg daily initiated early postoperatively for 12 months may be reasonable to improve vein graft patency (Class IIb, Level B-NR recommendation) 1, 2
• This is the weakest recommendation but supported by evidence showing improved saphenous vein graft patency at 3 months (91.6% vs 85.7% with aspirin alone) 3
• Meta-analyses demonstrated DAPT was associated with reduced vein graft occlusion and 30-day mortality compared to aspirin monotherapy 1, 2
• The benefit appears strongest for venous grafts, with one RCT showing particular benefit for radial artery grafts (43.8% occlusion with aspirin alone vs 10.5% with DAPT) 4

Aspirin Dosing and Timing

• Use low-dose aspirin 81 mg daily (range 75-100 mg) (Class I, Level B-NR) 1, 5
• Start within 6-24 hours after CABG once hemostasis is secured 5
• Aspirin significantly improves saphenous vein graft patency, particularly during the first postoperative year, and reduces mortality, MI, stroke, renal failure, and bowel infarction 1, 5
• Higher doses (100-325 mg) were used in older studies, but current evidence supports low-dose therapy to minimize bleeding risk while maintaining efficacy 1

Choice of P2Y12 Inhibitor

Clopidogrel

• Clopidogrel 75 mg daily is the most studied agent in CABG patients and appropriate for most situations 1, 5
• Reasonable alternative in patients intolerant or allergic to aspirin as monotherapy 1

Ticagrelor

• May be preferred over clopidogrel in ACS patients based on demonstrated cardiovascular mortality reduction 5
• In the PLATO trial post-hoc analysis, ticagrelor showed significant reduction in cardiovascular mortality compared to clopidogrel in CABG patients 1

Prasugrel

• Should be used in ACS patients not at high risk for bleeding and without history of stroke or TIA 1
• Retrospective analysis showed significantly lower 30-day mortality compared to clopidogrel in CABG patients 1
• Contraindicated in patients with prior stroke or TIA (Class III: Harm) 1

Timing of P2Y12 Inhibitor Resumption

• Resume as soon as deemed safe postoperatively, typically within 24-48 hours when bleeding risk is controlled 5
• In clinical trials, clopidogrel was initiated when chest tube drainage was ≤30 cc/h for 2 hours 3
• The benefit of aspirin on graft patency is lost if started more than 48 hours after surgery 1

Bleeding Risk Considerations

Important Caveats

• Major bleeding after surgery is more frequent with DAPT compared to aspirin monotherapy 1, 2
• Despite increased bleeding, studies showed no significant differences in total postoperative bleeding, transfusions, or reexploration rates between DAPT and aspirin alone 4, 3, 6
• The 30-day composite outcome (mortality or perioperative morbidity) was actually lower with DAPT (3.3% vs 7.1%) in one large VA study 6

Gastrointestinal Protection

• Consider adding a proton pump inhibitor (PPI) in patients at increased risk of GI bleeding (elderly, history of GI bleeding, chronic NSAID use, combination antithrombotic therapy) 5
• PPIs are effective in reducing GI bleeding risk with antithrombotic therapy 5

Common Pitfalls to Avoid

1. Do not delay aspirin initiation beyond 48 hours postoperatively - the benefit on graft patency is lost 1

2. Do not use enteric-coated low-dose aspirin - it has been associated with suboptimal platelet inhibition in 44% of patients; soluble aspirin is preferred 1

3. Do not add dipyridamole or warfarin to aspirin - they add nothing to graft patency and warfarin increases bleeding risk 1

4. Do not forget to resume P2Y12 inhibitor in ACS patients - the mortality benefit is significant and this is a Class I recommendation 1

5. Do not use prasugrel in patients with prior stroke or TIA - this is a Class III: Harm recommendation 1

Evidence Quality and Nuances

The strongest evidence (Class I recommendations) supports DAPT resumption in ACS patients and those with prior stents 1. The evidence for DAPT in SIHD patients is weaker (Class IIb), based primarily on graft patency outcomes rather than hard clinical endpoints 1, 2. However, meta-analyses consistently show improved vein graft patency with DAPT, and one large study demonstrated reduced 30-day mortality 1, 2, 6. The increased bleeding risk with DAPT appears manageable in clinical practice, with no significant increase in major bleeding complications requiring reexploration 4, 3, 6.