Even after long-term cessation of smoking, heavy smokers may fare worse after heart bypass surgery, according to Chinese scientists.

Smoking generates problematically high enzyme levels in the saphenous (leg) vein commonly used for coronary artery bypass grafting (CABG). Investigators found that, though noticeable progress in the return of these enzymes to normal levels at six months, it can sometimes take a year for the full enzyme-reversal process.

As such, researchers conclude that patients who have lived smoke-free for less than a year before surgery run the risk that the bypass grafting surgery will ultimately fail.

“Although recovery after smoking cessation appears somewhat disappointing, it illustrates exactly the importance of prompt smoking cessation for patients who will receive CABG,” said Sun Yongxin, M.D., and colleagues at Zhongshan Hospital at Fudan University in Shanghai.