When is revascularization indicated for left‑main coronary artery disease, and how are coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) chosen based on lesion severity, symptoms, and patient risk factors?

Left Main Coronary Artery Disease: Indications for Revascularization

Revascularization is mandatory for functionally significant left main stenosis (>50% diameter stenosis) in patients with LVEF >35%, as it improves survival, and CABG is the preferred modality over PCI except in anatomically low-complexity disease (SYNTAX score ≤22). 1

Survival-Based Indications for Revascularization

LVEF >35%

• Revascularization is Class I, Level A indicated for functionally significant left main stenosis to improve survival. 1
• This recommendation applies regardless of symptom status—the indication is based on mortality reduction, not symptom relief. 1
• Functional significance should be confirmed with FFR ≤0.80 or iFR when angiographic severity is intermediate (40-70% stenosis). 1, 2

LVEF ≤35%

• A Heart Team evaluation is mandatory to weigh revascularization versus medical therapy alone, considering coronary anatomy, correlation between CAD and LV dysfunction, comorbidities, life expectancy, and patient perspectives. 1
• CABG is Class I, Level B recommended over medical therapy alone in surgically eligible patients with multivessel CAD and LVEF ≤35% to improve long-term survival. 1
• PCI may be considered (Class IIb) in selected patients with LVEF ≤35% who are at high surgical risk or inoperable. 1

Choosing Between CABG and PCI

CABG is Preferred (Class I, Level A)

CABG is the overall preferred revascularization mode for left main disease due to lower risk of spontaneous MI and repeat revascularization. 1

Specific scenarios where CABG is strongly preferred:

• Low surgical risk patients with left main stenosis—CABG improves survival over medical therapy and is superior to PCI. 1
• High anatomic complexity (SYNTAX score >22)—CABG significantly reduces mortality, MI, and repeat revascularization compared to PCI. 1, 3
• Left main with multivessel disease—CABG is Class I recommended over medical therapy to improve survival. 1
• Diabetes mellitus with multivessel disease—CABG is Class I recommended over both medical therapy and PCI to improve symptoms and outcomes, regardless of anatomic complexity. 1, 3

PCI is Acceptable Alternative (Class I, Level A)

PCI is recommended as an alternative to CABG only in low-complexity left main disease (SYNTAX score ≤22) where equivalent completeness of revascularization can be achieved, given its lower invasiveness and non-inferior survival. 1, 2

PCI should be considered (Class IIa, Level A) in:

• Intermediate complexity left main disease (SYNTAX score 23-32) where PCI can provide equivalent completeness of revascularization to CABG. 1

PCI is reasonable (Class IIa, Level B) when:

• High surgical risk (STS-predicted mortality >5%) with low SYNTAX score (<22), ostial or trunk left main disease. 1
• Left main is the culprit lesion in UA/NSTEMI and patient is not a CABG candidate. 1

PCI is Contraindicated (Class III)

• Significant left main CAD with candidacy for CABG in stable patients with unfavorable anatomy (high SYNTAX score, complex bifurcation disease). 1
• High anatomic complexity with clinical characteristics predicting poor PCI outcomes. 1

Symptom-Based Indications

In patients with persistent angina despite guideline-directed medical therapy, revascularization of functionally significant left main stenosis is Class I, Level A indicated to improve symptoms. 1

This indication applies regardless of the survival benefit—symptom relief alone justifies revascularization in refractory angina. 1

Risk Stratification and Decision-Making Algorithm

Step 1: Assess Lesion Severity and Functional Significance

• Angiographic stenosis >50% is considered significant for left main disease. 1
• For intermediate stenosis (40-70%), FFR or iFR measurement is Class I recommended before intervention. 1, 2
• IVUS or OCT is Class I recommended when performing PCI on left main lesions to optimize technique. 1

Step 2: Calculate Risk Scores

• SYNTAX score is Class I, Level B recommended to assess anatomical complexity. 1
• STS score is Class I, Level B recommended to estimate surgical morbidity and 30-day mortality. 1

Step 3: Apply Decision Matrix

• SYNTAX ≤22 + Low surgical risk → CABG or PCI acceptable 1
• SYNTAX 23-32 + Low surgical risk → CABG preferred, PCI should be considered 1
• SYNTAX >32 + Low surgical risk → CABG strongly preferred 3
• Any SYNTAX + High surgical risk (STS >5%) → Consider PCI if SYNTAX ≤22 1
• Diabetes + Multivessel disease → CABG regardless of SYNTAX score 1, 3
• LVEF ≤35% + Surgically eligible → CABG preferred 1

Step 4: Heart Team Discussion

A multidisciplinary Heart Team discussion is Class I, Level C recommended to select the most appropriate revascularization modality based on patient profile, coronary anatomy, procedural factors, LVEF, preferences, and outcome expectations. 1

Common Pitfalls to Avoid

• Do not perform ad hoc PCI on left main lesions without Heart Team discussion, especially in stable patients with complex anatomy. 2
• Do not rely solely on angiographic appearance for intermediate left main stenosis—functional assessment with FFR/iFR is mandatory. 1, 2
• Do not choose PCI over CABG in diabetic patients with multivessel disease, as CABG provides superior outcomes regardless of anatomic complexity. 1, 3
• Do not underestimate the importance of complete revascularization—incomplete revascularization is associated with worse outcomes. 3
• Do not use controlled hypothyroidism or other stable comorbidities as justification for incomplete revascularization. 3
• Recognize that the Class I indication for CABG in left main disease is based on survival benefit, not just symptom relief. 3