What are the indications for Coronary Artery Bypass Grafting (CABG)?

Indications for Coronary Artery Bypass Grafting (CABG)

CABG is strongly indicated for patients with significant left main coronary artery stenosis, left main equivalent disease (≥70% stenosis of proximal LAD and proximal left circumflex), or proximal LAD stenosis with multi-vessel disease, as these anatomical patterns demonstrate clear mortality benefit over medical therapy alone. 1

Primary Indications Based on Anatomy

Class I Indications (Strong Evidence)

• Significant left main coronary artery stenosis (Level of Evidence: A) 1
• Left main equivalent: ≥70% stenosis of proximal LAD and proximal left circumflex artery (Level of Evidence: A) 1
• Proximal LAD stenosis with 2- or 3-vessel disease (Level of Evidence: B) 1
• Three-vessel disease, especially with reduced left ventricular function 1

Class IIa Indications (Reasonable to Perform)

• Proximal LAD stenosis with single-vessel disease (Level of Evidence: A) 1
• 1- or 2-vessel disease not involving proximal LAD when percutaneous revascularization is not optimal (Level of Evidence: B) 1

Class III Indications (Not Recommended)

• Stable angina with insignificant coronary stenosis (<50% diameter reduction) 1
• Single-vessel disease without significant proximal LAD stenosis 1

Indications Based on Clinical Presentation

Unstable Angina/Non-ST Elevation MI

• CABG should be performed for patients with significant left main or left main equivalent disease 1
• CABG is recommended when revascularization is not optimal or possible with ongoing ischemia despite maximal medical therapy 1

ST-Elevation MI

• Emergency/urgent CABG is indicated in:
  • Cardiogenic shock that can be performed within 18 hours 1
  • Life-threatening ventricular arrhythmias with ≥50% left main stenosis and/or triple-vessel disease 1
  • Failed PCI with ongoing ischemia or threatened occlusion with significant myocardium at risk 1

Poor Left Ventricular Function

• CABG provides significant benefit in patients with poor LV function who have:
  • Significant left main coronary artery stenosis 1
  • Left main equivalent disease 1
  • Proximal LAD stenosis with multi-vessel disease 1
  • Viable non-contracting revascularizable myocardium 1

Life-Threatening Ventricular Arrhythmias

• CABG is indicated for arrhythmias caused by:
  • Left main coronary artery stenosis 1
  • Three-vessel coronary disease 1
  • Proximal LAD disease with 1- or 2-vessel disease (Class I if resuscitated sudden cardiac death or sustained ventricular tachycardia) 1

Failed PCI Scenarios

• CABG should be performed after failed PCI with:
  • Ongoing ischemia or threatened occlusion with significant myocardium at risk 1
  • Hemodynamic compromise 1
  • Foreign body in crucial anatomic position (Class IIa) 1

Prior CABG Patients

• CABG is indicated for:
  • Disabling angina despite optimal medical therapy 1
  • Patent bypass grafts but with Class I indications for native-vessel disease 1
  • Atherosclerotic vein grafts with >50% stenosis supplying the LAD or large areas of myocardium 1

Special Considerations

Timing After MI

• In patients who have had an MI, CABG mortality is elevated for the first 3-7 days after infarction 1
• Beyond 7 days post-infarction, standard revascularization criteria apply 1

Technical Aspects

• Left internal mammary artery (LIMA) to LAD graft provides the best long-term prognostic benefit 2
• Internal mammary artery grafts show significantly lower occlusion rates compared to saphenous vein grafts, particularly in the LAD territory 3

Common Pitfalls and Caveats

1. Timing after MI: Performing CABG too early (within 3-7 days) after MI increases mortality risk unless there are specific urgent indications 1

2. Incomplete revascularization: In diffuse disease, even incomplete CABG can provide significant clinical improvement with acceptable graft patency rates, particularly with internal mammary artery grafts to the LAD 3

3. Ventricular tachycardia with scar: CABG is not recommended in ventricular tachycardia with scar and no evidence of ischemia 1

4. Failed PCI without ischemia: CABG is not recommended after failed PCI in the absence of ischemia or with inability to revascularize due to target anatomy or no-reflow state 1

5. Poor LV function without viable myocardium: CABG should not be performed in patients with poor LV function without evidence of intermittent ischemia or significant revascularizable viable myocardium 1

The decision for CABG must carefully weigh the potential survival benefit against operative risk, considering factors such as age, comorbidities, and the technical feasibility of revascularization. The use of internal mammary artery grafting to the LAD is particularly important as it provides superior long-term patency and improved survival compared to venous grafts 2, 3.