Right internal thoracic artery or radial artery? A propensity-matched comparison on the second-best arterial conduit

Objectives: We conducted propensity score matching to determine whether the use of the right internal thoracic artery (RITA) confers a survival advantage when compared with the radial artery (RA) as second arterial conduit in coronary artery bypass grafting. Methods: The study population included a highly selected low-risk group of patients who received the RITA (n = 764) or the RA (n = 1990) as second arterial conduit. We obtained 764 matched pairs that were comparable for all pretreatment variables. A time-segmented Cox regression model that stratified on the matched pairs was used to investigate the effect of treatment on late mortality. Results: After a mean follow-up of 10.2 +/- 4.5 years (maximum 17.3 years), survival probabilities at 5, 10, and 15 years were 96.4% +/- 0.7% versus 95.4% +/- 0.7%, 91.0% +/- 1.1% versus 89.1% +/- 1.2%, and 82.4% +/- 1.9% versus 77.2% +/- 2.5% in the RITA and RA groups, respectively. During the first 4 years, RITA and RA were comparable in terms of mortality (hazard ratio [HR], 1.00; 95% confidence interval [CI], 0.56-1.78; P = .98). However, after 4 years RITA was associated with a significant reduction in late mortality (HR, 0.67; 95% CI, 0.48-0.95; P = .02). RITA was superior to RA when the experimental conduit was used to graft the left coronary system (HR, 0.69; 95% CI, 0.47-0.99; P = .04) but not the right coronary system (HR, 0.98; 95% CI, 0.59-1.62; P = .93). Conclusions: In a highly selected low-risk group of patients, the use of the RITA as second arterial conduit instead of the RA was associated with better survival when used to graft the left but not the right coronary artery.