Coronary Artery Left Main

Left Main Coronary artery(LM): The left main coronary artery after arising from the left aortic sinus courses a short variable distance forward between the pulmonary artery and left auricle and then divides into its two principal branches – the left anterior descending artery and the left circumflex artery. A third branch vessel, the Ramus Intermedius (RI) , an artery that arises from the left main between the LAD and LCX, may be found in 37 % of the population. It supplies the free lateral wall of the left ventricle. The LM varies in length from 1 to 25 mms and has a diameter of 5-10 mm .

LMCA has the most elastic tissue of the coronary vessels, plain balloon angioplasty was associated with immediate procedural unpredictability and also with unacceptable high rates of restenosis and early mortality

Variations in LM anatomy :

In few cases, the LCA may be very short and bifurcates almost immediately.

In 0.41% of the cases, the LCA is not developed and there are two orifices in the left coronary sinus giving origin to the LAD and LCX.

In the majority of cases, the LM divides beneath the left atrial appendage, into the left anterior descending (LAD) and the circumflex arteries(LCX).

Aberrant origin
    • left main coronary artery or LAD from the right sinus of Valsalva or RCA, referred to as anomalous aortic origin of a coronary artery (AAOCA).
      •  interarterial (with or without an intramural course),
      • prepulmonic,
      • subpulmonic,
      • retroaortic, and
      • retrocardiac [



Extrinsic Compression


  • Arteritis
    • Kumar,G V R et al  Takayasu’s Arteritis with Ostial and Left Main Coronary Artery Stenosis . 2007; 34(4): 470–474.
  • Dissection
    • Iatrogenic
      • Namazi, M H et al  Iatrogenic left main artery dissection: A catastrophic complication . 2012 Winter; 17(4): 254–256.
  • Sinus of Valsalva Aneurysm