Bifurcation lesions (BFL) remain a true challenge to interventional cardiologists. For over two decades , at least a dozen strategies are being tried to conquer it without true success . . . if iam allowed to say that.
We often talk about side branch in BFLs.Ironically , the importance of side branch is largely determined by our cortical linguistic perception of the word “side”
The much famed Medina classification does little to clarify the importance of side branch with reference to left main vs non left main bifurcation lesions.
In true sense , both LAD or LCX can be side branches in left main BFL depending upon how one views it.
Commonsense would tell us, since LAD is a major vessel , LCX gets the side branch tag by default.
However, If LAD is diminutive, or its serving a infarcted , non functional zone and if LCX is really big and dominant, it has every right to reject the humiliation of being refered to as a sidekick.
Note , in non left main BFL there is no much confusion since main branch continues as main and side branch just exit.
Final message
Interventional cardiologists use the term “side and main branch ” in variety of ways .Though, it could mean vitally important things , oftentimes its simply semantics prevailing over complex coronary hemodynamics.
Dr.S.Venkatesan MD 
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