How can a Physician Assistant (PA) starting in cardiac surgery commit to memory the coronary arteries used in Coronary Artery Bypass Grafting (CABG) for adult patients with coronary artery disease and potential comorbidities such as hypertension, diabetes, and hyperlipidemia?

Memorizing Coronary Arteries Used in CABG: A Practical Guide for Cardiac Surgery PAs

Use the mnemonic "LIMA to LAD is LAW" as your foundation—the left internal mammary artery (LIMA) to the left anterior descending (LAD) artery is the gold standard conduit that must be used in virtually all CABG cases because it provides superior long-term outcomes and survival. 1

Essential Conduit-Target Vessel Pairings

Primary Conduits (Learn These First)

• Left Internal Mammary Artery (LIMA): Always grafted to the LAD artery—this is non-negotiable and represents the single most important graft in CABG surgery 1, 2
• Right Internal Mammary Artery (RIMA): Typically used for the second most important target, often the left circumflex or right coronary artery system 1
• Radial Artery: Harvested from the non-dominant arm and used as an additional arterial conduit for high-grade stenoses, commonly to diagonal branches, obtuse marginal branches, or posterior descending artery 1
• Saphenous Vein Grafts (SVG): Used for remaining targets after arterial conduits are exhausted, though they have inferior long-term patency compared to arterial grafts 3, 2

Target Coronary Territories to Memorize

The Three Main Systems

• Left Anterior Descending (LAD) Territory: Includes LAD itself plus diagonal branches—LIMA is the mandatory conduit here 1
• Left Circumflex Territory: Includes obtuse marginal (OM) branches—typically receives RIMA, radial artery, or SVG 1
• Right Coronary Artery (RCA) Territory: Includes posterior descending artery (PDA) and posterolateral branches—receives radial artery or SVG 1

Practical Memory Framework

Hierarchical Approach to Conduit Selection

Think in order of graft durability:

1. LIMA → LAD (always first, improves survival) 1, 2
2. RIMA or Radial → Second most critical lesion (usually circumflex or RCA territory) 1
3. Additional arterial grafts → Remaining significant stenoses (>70% diameter narrowing or >50% for left main) 4
4. SVG → Fill in remaining targets when arterial conduits exhausted 3

Anastomosis Locations to Remember

• Proximal anastomoses: Created on the ascending aorta (for SVGs and sometimes radial arteries) 1
• Distal anastomoses: Created on target coronary arteries beyond the stenosis—this is critical for graft patency 1
• In-situ grafts: LIMA and RIMA remain attached to their origin (subclavian artery) and are anastomosed only distally 1, 2

Common Pitfalls to Avoid

• Never forget: LIMA to LAD is mandatory unless there are exceptional contraindications—failure to use this conduit represents substandard care 1
• Graft failure patterns: SVGs have higher failure rates (especially after 5-10 years), so arterial grafts are strongly preferred when technically feasible 3, 2
• Sequential grafting: A single conduit can be anastomosed to multiple targets (e.g., SVG to diagonal then OM)—this is common practice but requires understanding the coronary anatomy 1

Clinical Context for Decision-Making

Patient Factors Affecting Conduit Choice

• Diabetes mellitus: These patients particularly benefit from complete arterial revascularization when possible, as they have worse outcomes with SVG-only grafting 5
• Radial artery contraindications: Cannot use if patient has inadequate collateral flow via ulnar artery (check Allen test preoperatively) or requires future arteriovenous fistula for dialysis 1
• Elderly or high-risk patients: May receive more SVGs due to shorter life expectancy making long-term graft patency less critical 4

Anatomical Considerations

• Target vessel quality: Distal vessels must be >1.5mm diameter with adequate runoff for successful grafting 4
• Severity threshold: Bypass grafting is indicated for ≥70% diameter stenosis in major vessels or ≥50% in left main coronary artery 4