Left main coronary artery

The left main coronary artery (LMCA) or left coronary artery (LCA) is one of the two main coronary arteries that supply the heart with oxygenated blood.

Gross anatomy

Origin

It is a branch of the ascending aorta, with its normal origin in the left aortic sinus, just superior to the aortic valve .

Course

The left main coronary artery runs for 5-10 mm as it passes to the left and posterior to the pulmonary trunk before bifurcating .

Branches

• left anterior descending artery (LAD)
• left circumflex artery (LCx)

Coronary dominance

Most hearts are right dominant, where the posterior descending artery (PDA) is supplied by the right coronary artery (RCA). However up to 20% of hearts may be left dominant, where the PDA is supplied by the LAD or LCx, or codominant, where a single or duplicated PDA is supplied by branches of both the RCA and LAD/LCx.

For a more in depth discussion of coronary dominance, see the article coronary arterial dominance.

Variant anatomy

Anatomical variations of the LMCA include :

• in ~15% of patients the LMCA trifurcates
  • left anterior descending artery
  • left circumflex artery
  • ramus intermedius artery
• multiple ostia: separate origin of LAD and LCx (i.e. no LCA)
• single coronary artery (very rare)
• anomalous origin of LMCA from pulmonary artery known as ALCAPA (anomalous origin of the LCA from the pulmonary artery)
  • very rare (1 in 300,000 births); high morbidity and mortality in first 12 months of life
• origin of LMCA from right coronary sinus (see Case 1) or non-coronary sinus

See main article: congenital coronary artery anomalies.