Coronary artery is the life line of the heart.The size , branches and the course are predetermined . Generally it follows a pattern , but still it is believed every human has a unique coronary finger print. (When retinal blood vessels can do this . . . why not the coronary ? )
When the left main bifurcates it has to share its resources equally between the two daughter vessel (Not exactly . . . LAD is widow maker can’t be a daughter !)
The logic would say LAD demands more as it has more territorial commitment.But if LCX fights for equality share there is a potential conflict here.But when LCX is very aggressive and demands much more than it deserves the issue becomes further complex
See how this LCX gets bulk of the blood flow from Left main and no doubt this man came with NSTEMI and LAD region ischemia while his posterior circulation is comfortably placed with excess blood.
One suggested formula (not validated ) is diameter of LCX + LAD will be at-least 150% of left main diameter .
1.5 x Left main diameter = (LAD + LCX diameter)
This amounts to 50% gain in diameter as it bifurcates .
Trifurcation further increases the width conferring a hemodynamic advantage
What is the implication of unequal bifurcation Left main ?
Hemodynamically there could be diversion of flow into a larger orifice .But ultimately since the blood flow is determined by the resistance arterioles at myocardial bed there may not be any practical significance . In pathological situations there could be a some impact due to stealing . Large LCX is more common with left dominant circulation .