God creates life with infinite variation . The heart gets bulk of its blood supply from the left coronary artery , which divides into two after a short course. Bifurcation is the rule . Left main becomes left circumflex and LAD in about in 85-90 %.
Note the left main divides into 3 equal caliber vessels.very lucky to have such a branching pattern !Distal left main is unloaded by three large ostia . This makes stasis of blood in left main very unlikely . LAO caudal view
Note : The OMs are small in these people. RAO caudal view
Few men and women are blessed with three branches from LCA . The anatomical and physiological importance of this branching pattern is not well analysed in the literature .There could be few advantages of having a trifurcation instead of bifurcation .
- Left main impedence is less in trifurcation . This is due to the fact , left main empties into three distinct ostia rather than two.The combined cross sectional area of these three ostia confers a hydrodyamic advantage.
- The importance of any proximal LAD lesion in these patients , is negated by 33 % as two other vessels are there to take care the rest of the heart.
- A large Ramus usually supplies a vast area in the angle between LAD and LCX. This has a potential to protect against ventricular fibrillation during acute occlusion of LAD by providing electrical stability .
Disadvantage of trifurcation !
- It is also a fact , people with a large Ramus may have a trade off by having a diminutive diagonal or OM .
- A trifurcation with a small calibered ramus can often be a disadvantage , as it is prone for atherosclerosis since it restricts left main flow by venturi effect . (The first rule of atherosclerosis states its prone at branching points)
* A related blog elsewhere in my site . The explanations offered above are based on personal observation .
Dr.S.Venkatesan MD 