Coronary circulation is an enigma . This is true even after 50 years of coronary angiography. What we visualise in CAG is only a fraction , when compared with what we do not see ! The intricacies of coronary collateral circulation and micro circulation is comparable only to the ultimate force of invisibility “The God ”
But , we will never ever believe what we do not see . . . but we have to accept the following fact . How is it possible for some of the coronary arteries to maintain a near normal blood flow from a donor (Contralateral ) coronary artery in spite of 100 % occlusion ? Is it not common to see TIMI 3 flow even with 99 % occlusion .(Link to related article in this blog and video ) . This is because the coronary vascular bed has an extraordinary capacity to drop its distal pressure to negate the effects of obstruction.
Does the distal vascular bed anatomy and physiology same in RCA and LCA ?
We presume it so . The problem in medical science is , these presumptions often become facts in due course ! Now we have (It is in fact 30 years old !) RCA has lesser ability to withstand the stress of stenosis than LCA.
The prime reason for this observed difference could be the LCA has a well developed microvascular bed which can reduce the distal coronary resistance .(Again , this is my presumption . . . !!! )
This interesting article was published in Circulation 1980 .
Dr.S.Venkatesan MD 
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