Collateral circulation is usually not felt by the patient when it is established, and can sometimes occur after the onset of the disease. The main manifestation of collateral circulation is the creation of side veins in the blood vessels, resulting in a new way of blood circulation. The phenomenon of collateral circulation is caused by the fact that the main trunk of the blood vessel gives off other pathways that are different in form from the main trunk. When there is a blockage in the main trunk of the blood vessel, blood can enter and thus circulate from the side branches, and then flow to the distal part of the blood vessel in order to prevent the phenomenon of necrosis of the tissues supplied with blood, and the common causes are conditions such as coronary collateral circulation. Side branch circulation is an abnormal situation, when there is such a manifestation of side branch circulation, you should go to the hospital in time for examination and active treatment to avoid aggravation of the condition.