Smoking interferes with bypasses
It's why you need to quit before surgery.
Leg veins are often used in bypass surgery to route blood around a blockage. A study in The Annals of Thoracic Surgery found that smoking harms the quality of leg veins used as bypass grafts. According to the researchers, leg veins require a minimum of six months after smoking has stopped to begin returning to normal and are still not completely healthy after 12 months. Using veins for bypass surgery within this time period increases the risk the grafts will fail, and the operation will need to be repeated.