ABCD classification for left main bifurcation lesions

A new classification system for LM bifurcation/ trifurcation lesions has been proposed. 

1. Following nomenclature has been suggested: 

    A/a for LM coronary artery

    B/b for LAD artery

    C/c for left circumflex coronary artery

    D/d for ramus intermedius artery (intermediate branch)

Whether a capital or small letter would be used, depends upon the diameter of the vessel as explained below. 

2. Each artery is given one of the above-mentioned letters if the stenosis is considered to be significant (i.e., >70% in lumen reduction visually,  or based on FFR or other resting indices, cCT-cFFR, IVUS, OCT).

3. If the stenosis is not considered significant, no letter would be assigned.

4. A capital letter is used if the vessel diameter is ≥3.5 mm, while a small letter is used if the diameter is smaller than 3.5. 

5. The image below has significant stenosis in all three vessels i.e LM, LAD and LCx. LM and LAD arteries are more than 3.5 mm in diameter, whereas LCx is smaller than 3.5 mm. The ABCD classification will label it as ABc. 

6. The image below has significant stenosis in only the left anterior descending artery which is more than 3.5 mm in diameter. The ABCD classification will label it as simply B. 

Reference: 

1. Ludwig J, Mohamed M, Mamas MA. Left main bifurcation lesions: Medina reclassification revisited-as easy as ABC [published online ahead of print, 2020 Jul 4]. Catheter Cardiovasc Interv. 2020;10.1002/ccd.29121. doi:10.1002/ccd.29121