Collateral circulation is established in:

Collateral channels are blood vessels which allow blood to flow directly from one aery to another. Aeries in the lungs, kidneys, and spleen are end-aeries. Such aeries have no anastomoses with their neighboring aeries; collateral circulation is not seen in these organs. In the normal human hea there are no functional intercoronary channels or existing collaterals. Sudden blockade of an aery may lead to ischemia and necrosis of the corresponding poion of myocardium. However, if narrowing of a coronary aery occurs slowly, there may be development of collateral vessels. Collateral channels have also found to be developed in skeletal muscle circulation