After the blood flow of the main blood vessel (artery or vein) in a certain part of the body is blocked, the blood vessels of the original anastomotic branch of the part expand and form bypasses, so that the blood passes through these bypasses in a roundabout way and restores the circulation, this circulatory pathway is called “collateral circulation”, also called “compensatory circulation This circulatory pathway is called “collateral circulation”, also known as “compensatory circulation”. Inadequate development of the collateral circulation means that these bypasses are not sufficiently developed, which still affects the circulation and can cause various cardiovascular diseases. What are the easily confused collateral circulation? There are mainly coronary collateral circulation, collateral circulation of portal vein, collateral circulation of cerebral artery and collateral circulation of aorta, if the collateral circulation is not fully developed, it will cause related diseases. 1.Coronary collateral circulation Coronary collateral circulation often occurs when the coronary artery is narrowed or secondary to thrombosis caused by coronary atherosclerosis. In this case, the lumen of the original interbranch coronary artery anastomosis branch can be dilated and the wall thickened. The relationship between coronary collateral circulation and the prognosis of coronary heart disease (CHD) has been studied in the literature. Based on the selective coronary angiography (SCA) results, 98 patients with SCA were divided into normal control group (non-CHD group), CHD without collateral circulation group, and CHD with collateral circulation group, and the clinical data of each group were analyzed. RESULTS: In the CHD group compared with the non-CHD group, except for the higher incidence of diabetes mellitus (with or without collateral circulation) (P<0.01), the differences in other CHD predisposing factors were not significant (P>0.05); the differences in the occurrence of major CHD predisposing factors and unstable angina pectoris (UAP) in patients with collateral circulation compared with those without collateral circulation were not significant (P>0.05 ); however, the incidence of cardiac insufficiency, myocardial infarction, and ventricular wall tumor was significantly increased in patients without collateral circulation (P<0.01); secondary occlusion and complete occlusion were mainly seen in those with collateral circulation; left anterior descending branch lesions were predominant in patients with collateral circulation, and right coronary artery lesions were predominant in patients without collateral circulation. The findings suggest that the presence or absence of collateral circulation is closely related to the prognosis of CHD patients. 2.Side-branch circulation of portal vein When portal vein flow is obstructed, if the obstruction occurs gradually, the anastomotic branch between portal vein and vena cava will be dilated, and through "side-branch circulation", most of the blood can flow into the right ventricle without going through the liver. The common cause of obstruction is intrahepatic, which is seen in hepatic sclerosis. In normal condition, about all the blood from the portal vein enters the liver, but in hepatic sclerosis, only 13% of the portal blood enters the liver, and most of the rest flows directly into the right heart through the collateral veins. 3.Collateral circulation of cerebral arteries There are many anastomosing branches between the various arteries of the brain. In cases such as atherosclerosis and occlusive endarteritis, the lack of blood supply to the brain can be improved through the "collateral circulation" because the arterial blockage occurs gradually at this time. 4.Collateral circulation of the aorta The "collateral circulation" of the aorta occurs when the aorta is congenitally narrowed. The constriction occurs distal to the opening of the ductus arteriosus, which is already atretic. In this case, the main role of the "collateral circulation" is played by the subclavian artery and its branches, such as the scapular artery and the internal thoracic artery, which are greatly dilated and curved to anastomose with the branches of the descending aorta, such as the intercostal artery and the deep abdominal wall artery. The anastomotic branches can be roughly divided into three groups: (i) the transverse cervical artery through the subclavian artery, the branches of the lateral thoracic artery and the superior and inferior scapular arteries anastomose with the intercostal arteries of the thoracic aorta. (ii) Through the branches of the internal thoracic artery the superior ventral wall artery, the musculo-diaphragmatic artery and the anterior branch of the intercostal artery anastomose with the intercostal artery of the thoracic aorta, the superior diaphragmatic artery and the inferior ventral wall artery of the external iliac artery. (iii) Anastomosis through the spinal branch of the vertebral artery with the spinal artery emanating from the branch of the interaortic artery.