The saphenous vein, the longest superficial vein in the body, runs from the ankle to the base of the thigh. It is one of the most commonly used “bridging” vascular materials in coronary artery bypass surgery due to its small curvature, sufficient length, and caliber that matches that of the coronary arteries. The human body has two sets of venous return systems in the lower extremities: the deep veins and the superficial veins. Taking out the superficial vein, i.e. the saphenous vein, one set of venous return system is gone, which will inevitably cause venous return obstruction, and this is why the lower limbs will be swollen after the operation. However, due to the rich traffic side branches between the two sets of deep and superficial venous return systems, after a sufficiently long period of postoperative recovery, the side branch circulation will be more abundant, and the deep veins will be able to play a complete compensatory role, which will have no great influence on the venous return of lower limbs, and will not affect the lower limbs’ venous blood circulation. The deep veins are able to fully compensate for this and will not have much effect on the venous blood return of the lower limbs and will not affect the motor function of the lower limbs. However, it is true that there are some patients whose deep venous system cannot fully compensate for the function of the lower limbs, and the patients have long-term swelling of the lower limbs, in which case, the patients need to insist on elevating the affected limbs when they sleep for a long period of time, and insist on wearing medical compression stockings for a long period of time when they go down to the ground.