Why is the saphenous vein used for cabg?

Its length: The great saphenous vein is used for CABG because of its length and size and because you can live without it. There are limitations to its use though. If it has become abnormal because of having varicose veins, it isn't used. Nowadays, stents are often used where veins used to be required or arteries from inside the chest or the wrist are used instead.

Its yours!: As surgeons, we always prefer to use the patient's own tissue rather than something foreign, as it is more resistent to infection.

Saphenous vein: the reason this vein is being used, if it is normal, is because this vein of the lower extremity is not needed for vein blood flow return back towards the heart. This makes it suitable to replace and artery of the heart with this vein and allow the vein to then become functioning like an artery.