Long-term survival of non-smokers undergoing coronary artery bypass surgery

Objectives: We sought to investigate long-term survival of non-smokers undergoing coronary artery bypass surgery (CABG).

Methods: A prospective database of consecutive patients was retrospectively analysed and cross correlated with the UK strategic tracking service to evaluate survival after primary CABG. Univariate, multivariate and a propensity analyses were performed.

Results: We analysed 13 337 primary CABG procedures. Median follow-up was 7 years. Kaplan-Meier survival curves demonstrate that non-smokers have a significantly improved long-term survival compared with ex- and current smokers, P < 0.0001. Cox regression analysis identified smoking status, age, diabetes, ejection fraction (EF), body mass index, cerebrovascular disease, dialysis, left internal mammary artery (LIMA) non-usage, postoperative creatinine kinase muscle-brain isoenzyme (CKMB), radial artery usage, preoperative rhythm, forced vital capacity (FVC) and logistic EuroSCORE as significant risk factors determining long-term survival. Propensity matching resulted in 3575 non-smokers being matched 1:1, with ex-smokers. After matching, univariate analysis demonstrated the significantly worse long-term survival of ex-smokers compared with non-smokers, P < 0.0001. Cox regression analysis identified smoking status, age, postoperative CKMB, cerebrovascular disease, dialysis, diabetes, EF, FVC, LIMA non-usage, radial artery used, sinus rhythm and logistic EuroSCORE as significant risk factors determining long-term survival. Survival by smoking status plotted at the mean of the covariates, prepropensity matching, demonstrated that non-smokers had a significantly better long-term survival than ex-smokers, P < 0.0001; however, after propensity matching, non-smokers under 65 years of age had a significantly worse long-term survival compared with ex-smokers, P < 0.0001.

Conclusions: Non-smokers under the age of 65 years of age have significantly worse long-term survival compared with ex-smokers after risk factor adjustment. We speculate that this is because ex-smokers have had the causative factor, smoking, removed, but non-smokers have not.