What are the indications for Coronary Artery Bypass Grafting (CABG) in adults with severe coronary artery disease, particularly those with significant left main disease, three-vessel disease, or two-vessel disease with proximal left anterior descending artery involvement?

CABG Indications in Severe Coronary Artery Disease

CABG is the definitive treatment for left main disease with high anatomic complexity (SYNTAX score ≥33), all three-vessel disease regardless of complexity, and two-vessel disease with proximal LAD involvement when left ventricular function is impaired (EF <50%) or extensive ischemia is documented. 1

Left Main Disease: Complexity Determines the Approach

For left main disease, your decision hinges entirely on the SYNTAX score:

• Low complexity (SYNTAX 0-22): PCI is equivalent to CABG and recommended as an alternative given lower invasiveness 1
• Intermediate complexity (SYNTAX 23-32): PCI should be considered if complete revascularization is achievable 1
• High complexity (SYNTAX ≥33): CABG is mandatory; PCI is contraindicated (Class III recommendation) 1, 2

The 2024 ESC guidelines represent a significant shift toward PCI for anatomically favorable left main disease, but this applies only when complete revascularization matches what CABG would achieve 1. Do not attempt PCI in bifurcation left main disease with high SYNTAX scores—the procedural complications and long-term outcomes are unacceptable. 3

Three-Vessel Disease: CABG is Standard

CABG receives a Class I recommendation for all patients with three-vessel disease, with survival benefit amplified when LVEF <50%. 1

The critical nuance here involves diabetes and anatomic complexity:

• Diabetic patients with three-vessel disease: CABG is mandatory over PCI regardless of SYNTAX score when complexity is intermediate-to-high (>22) 1, 4
• Non-diabetic patients with low SYNTAX (0-22): PCI becomes a Class IIb option (uncertain benefit), but CABG remains preferred 1, 4
• Complex three-vessel disease (SYNTAX >22): CABG is strongly preferred (Class IIa) over PCI in all patients who are acceptable surgical candidates 1

The survival benefit in three-vessel disease exists regardless of symptom severity—do not defer CABG in asymptomatic or mildly symptomatic patients when anatomic criteria are met. 4, 2

Two-Vessel Disease with Proximal LAD: Function and Ischemia Matter

CABG is Class I for two-vessel disease with proximal LAD involvement when either LVEF <50% or demonstrable ischemia exists on noninvasive testing. 1

Without these features, the recommendation weakens:

• With extensive ischemia documented: CABG is Class IIa (reasonable) 1
• Without extensive ischemia: CABG is Class IIb (uncertain benefit); both CABG and PCI have similar evidence 1

The proximal LAD is the critical determinant—two-vessel disease NOT involving proximal LAD has substantially weaker indications for CABG (Class IIb without extensive ischemia), with PCI being the recommended approach (Class I). 1

Technical Mandate: LIMA to LAD is Non-Negotiable

In every CABG procedure, the left internal mammary artery (LIMA) must be grafted to the LAD—this is a Class I recommendation with long-term patency exceeding 90% at 10 years. 1, 2, 5

For complete revascularization in three-vessel disease:

• LAD receives LIMA (mandatory) 5, 6
• Left circumflex and RCA typically receive saphenous vein grafts, though radial artery grafts show superior patency (89% vs 65-80% at 4-5 years) 5
• Bilateral internal mammary arteries (BIMA) provide survival benefit in younger patients with multivessel disease 5

Avoid endoscopic vein graft harvesting—it associates with higher graft failure rates and adverse clinical outcomes. 5

Timing Considerations: The 3-7 Day Window

Do not perform elective CABG within 3-7 days of acute MI unless ongoing ischemia with hemodynamic compromise exists—surgical mortality is elevated during this window. 4, 2

Emergency CABG is indicated for:

• Cardiogenic shock within 18 hours when anatomy is unsuitable for PCI 2
• Failed PCI with ongoing ischemia or hemodynamic compromise 4
• Life-threatening ventricular arrhythmias in the presence of three-vessel disease 4

Common Pitfalls to Avoid

Do not withhold CABG based on age alone—when surgical risk is acceptable, the benefit-to-risk ratio remains favorable in elderly patients 4, 2. The Society of Thoracic Surgeons (STS) predicted operative mortality score should guide surgical risk assessment, not chronologic age 1.

Do not perform CABG for single-vessel disease without proximal LAD involvement—this is a Class III (harm) recommendation unless the patient has refractory symptoms and is not a PCI candidate 1.

Withhold clopidogrel for 5 days before CABG when clinical circumstances permit to reduce bleeding complications 1.