Coronary artery disease is the major determinant of human health and longevity in this modern era! Obstruction of a coronary artery either sudden or gradual forms the basis of CAD .
When a free flowing river stumbles upon an obstruction , it does not die , it finds it’s way to the sea. Similarly , God is kind enough to provide alternate channels for blood flow to heart at times of crisis .Contrary to the perception , collaterals develop not only in chronic occlusions but also in acute occlusions.
A person who dies due to a primary VF few minutes after an acute occlusion is in all probability experiences his fate ! While those who survive are protected by the immediate recruitment of collaterals and this prevents the remote myocardium from triggering a VF.
In chronic CAD, the collaterals are much more effective. Now we have evidence with OAT and COURAGE *trials for this. Some times , the LAD is fully supported by the RCA the flow is better than a graft.
*These trials showed us opening occluded coronary arteries routinely do not confer additional benefits.
Coronary collateral circulation is most poorly understood phenomenon in cardiology. But it comes as helping hand whenever required only for those humans who deserve it ! God has kept the secrets of coronary collateral circulation with himself !
A excellent article on natural by pass from circulation patient pages.
http://circ.ahajournals.org/cgi/content/full/116/11/e340
Link to related you tube video
Dr.S.Venkatesan MD 
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