The prevalence and clinical importance of an "additional" terminal branch of the left coronary artery.

The left coronary artery (LCA) usually divides into two (anterior interventricular artery [AIA] and left circumflex [LCx] artery) or less frequently into the AIA, LCx,and one or more "additional" terminal branch/es (ATBs). These ATBs of the LCA have no unanimity regarding their anatomical nomenclature. There is a lack of common consensus on the criteria used for their definition, and they are also absent from the current Terminologia Anatomica (1998). This study, therefore,aimed to document the prevalence of the ATBs of the LCA, discuss their clinical importance, and propose an anatomical nomenclature. This study was conducted by reviewing 367 coronary angiograms. The termination patterns of the LCA were classified into 3 categories based on the number of their branches, viz. (a) bifurcation78.2%, (b) trifurcation 20.4%, and (c) quadrifurcation 1.4%, respectively. The presence of an ATB was recorded in 21.8% of the angiograms. The identification of this vessel may be of clinical importance because the extent of its supply may decrease the effect of occlusion of the LCx artery and AIA on the myocardium.The term "left ramus medianus artery" is proposed as the nomenclature for the ATB of the LCA.