A new study has shown that changes found in smokers’ lungs can linger and affect the outcome of heart surgery even a year after quitting.

The study, published in the journal The Annals of Thoracic Surgery, looked at the outcomes of 208 patients who received bypass surgery (CABG). The patients were divided into six groups based on the amount they smoked or their prior smoking habits.

Heavy smokers were found to have increased matrix metalloproteinase enzyme levels, which have been linked to vein graft failure. However, even those patients who had quit smoking before undergoing heart surgery were still found to have dysregulation of enzymes.

“Although recovery after smoking cessation appears somewhat disappointing, it illustrates exactly the importance of prompt smoking cessation for patients who will receive CABG,” said the study’s authors.

Though vein enzymes may gradually return to normal, the researchers stated that at least six months are needed to see “noticeable” vein recovery after quitting smoking. Even a year after quitting, vein enzymes do not completely recover to normal levels.

[This study] may provide the evidence for encouraging the use of more arterial grafts [rather than vein grafts] when heavy smokers undergo CABG,” said the study’s authors.

According to researchers, vein grafts are the most commonly used vessels for bypass surgery. Though the new study may suggest using other vessels for the one-in-three worldwide adults who smokes, the researchers suggest that quitting smoking is the better option.

“Smoking cessation is important to maintain cardiovascular health in a preventative manner and also to maximize the results of bypass surgery in patients who will benefit from this operation,” said Dr. Shahab Akhter of The University of Chicago Medicine.