What are the strategies for coronary artery bypass grafting (CABG) after acute coronary syndrome?

CABG Strategies After Acute Coronary Syndrome

Emergency CABG is recommended for ACS patients when primary PCI has failed or cannot be performed, when coronary anatomy is suitable for CABG, and when persistent ischemia of a significant myocardial area or hemodynamic instability refractory to medical therapy is present. 1

Emergency CABG Indications (Class I)

Emergency CABG is mandated in the following scenarios:

• Failed or impossible PCI with persistent ischemia of significant myocardium and/or hemodynamic instability despite maximal medical therapy 1
• Mechanical complications including ventricular septal rupture, mitral valve insufficiency from papillary muscle infarction/rupture, or free wall rupture 1
• Cardiogenic shock in patients suitable for CABG, regardless of time interval from MI to shock onset or MI to CABG 1
• Life-threatening ventricular arrhythmias (ischemic origin) with left main stenosis ≥50% and/or 3-vessel CAD 1
• Left main or triple-vessel disease particularly with left ventricular dysfunction 2

Reasonable CABG Indications (Class IIa)

• Multivessel CAD with recurrent angina or MI within first 48 hours of STEMI presentation as alternative to delayed strategy 1
• Patients >75 years with ST-elevation or left bundle branch block suitable for revascularization, irrespective of time from MI to shock onset 1
• NSTE-ACS with multivessel disease, especially with diabetes and higher coronary complexity 3

Contraindications to Emergency CABG (Class III: Harm)

Do NOT perform emergency CABG in these situations:

• After failed PCI without ischemia or threatened occlusion 1
• After failed PCI if revascularization is impossible due to target anatomy or no-reflow state 1
• Persistent angina with small viable myocardium and hemodynamic stability 1
• No-reflow state (successful epicardial but unsuccessful microvascular reperfusion) 1

Timing Considerations

For NSTE-ACS: CABG can be performed as early revascularization strategy within 24-48 hours for high-risk patients, though PCI is generally preferred initially 2. The decision between immediate versus staged CABG depends on hemodynamic stability and extent of jeopardized myocardium 1.

For STEMI: Primary PCI is preferred when achievable within 120 minutes of first medical contact 2. CABG becomes the primary option only when PCI is not feasible or has failed 2.

Critical timing caveat: Prior PCI within 24 hours before CABG significantly increases mortality (14.5% vs 7.4% without prior PCI) and major adverse cardio-cerebral events (25.6% vs 16.4%) 4. Failed PCI before CABG carries even higher risk with 14.1% mortality and 41.3% major adverse events 4.

Technical Approach

Radial access is the standard approach for initial coronary angiography unless procedural contraindications exist 1, 2.

Off-pump CABG (OPCAB) can be performed safely in selected ACS patients requiring emergency revascularization, with mean operative time of 195 minutes versus 286 minutes for on-pump 5. OPCAB is particularly indicated for patients at high risk for cardiopulmonary bypass complications 5.

Complete revascularization should be achieved whenever possible. For stabilized STEMI patients with multivessel disease, complete revascularization is recommended as staged PCI (Class I) or staged CABG (Class IIa) 2.

Conduit Selection

• Left internal mammary artery (LIMA) to LAD is mandatory for improved survival and patency 1
• Radial artery is recommended over saphenous vein for the second most important non-LAD vessel to improve long-term outcomes 1
• Use oral calcium channel blockers for first postoperative year following radial artery grafting 1

Antiplatelet Management Pitfalls

Critical bleeding risk: Recent potent antiplatelet therapy significantly increases surgical bleeding risk 1:

• Clopidogrel: Withhold 5 days before surgery when possible 1
• GP IIb/IIIa inhibitors: Eptifibatide should be discontinued ≥2 hours before bypass; abciximab requires platelet transfusions 1
• Low-molecular-weight heparin: Associated with greater postoperative hemorrhage risk 1

However, when hemodynamic instability or ongoing ischemia threatens life, the need for surgery supersedes bleeding risk 1.

Post-CABG antiplatelet therapy: Dual antiplatelet therapy (DAPT) reduces ischemic events but requires careful bleeding risk assessment 3. Shorter DAPT duration (1-3 months) with transition to P2Y12 inhibitor monotherapy is reasonable in selected patients to reduce bleeding 1.

Hemodynamic Support

Intra-aortic balloon pump (IABP): Can stabilize patients preoperatively, allowing recovery of ischemic myocardium and transition from emergency to urgent surgery with better outcomes 6. However, routine IABP use in cardiogenic shock without mechanical complications is NOT recommended 1, 2.

Intraoperative transesophageal echocardiography is recommended for monitoring hemodynamic status, ventricular function, and regional wall motion 1.

Prognostic Factors

Preoperative cardiogenic shock is the only significant independent predictor of postoperative death (odds ratio 7.33) 5. The selection of on-pump versus off-pump does not correlate with operative mortality 5.

Long-term outcomes favor CABG over PCI in multivessel ACS, with 5-year survival rates of 72.5% in AMI and 89.6% in unstable angina 6. Complete revascularization improves both perioperative and long-term results 6.