A meta-analysis of adjusted hazard ratios from 20 observational studies of bilateral versus single internal thoracic artery coronary artery bypass grafting

ObjectiveIn 2001, a landmark meta-analysis of bilateral internal thoracic artery (BITA) versus single internal thoracic artery (SITA) coronary artery bypass grafting for long-term survival included 7 observational studies (only 3 of which reported adjusted hazard ratios [HRs]) enrolling approximately 16,000 patients. Updating the previous meta-analysis to determine whether BITA grafting reduces long-term mortality relative to SITA grafting, we exclusively abstracte, then combined in a meta-analysis, adjusted (not unadjusted) HRs from observational studies.MethodsMEDLINE and EMBASE were searched until September 2013. Eligible studies were observational studies of BITA versus SITA grafting and reporting an adjusted HR for long-term (≥4 years) mortality as an outcome. Meta-regression analyses were performed to determine whether the effects of BITA grafting were modulated by the prespecified factors.ResultsTwenty observational studies enrolling 70,897 patients were identified and included. A pooled analysis suggested a significant reduction in long-term mortality with BITA relative to SITA grafting (HR, 0.80; 95% confidence interval, 0.77 to 0.84). When data from 6 pedicled and 6 skeletonized internal thoracic artery studies were separately pooled, BITA grafting was associated with a statistically significant 26% and 16% reduction in mortality relative to SITA grafting, respectively (P for subgroup differences = .04). A meta-regression coefficient was significantly negative for the proportion of men (−0.00960; −0.01806 to −0.00114).ConclusionsBased on an updated meta-analysis of exclusive adjusted HRs from 20 observational studies enrolling more than 70,000 patients, BITA grafting seems to significantly reduce long-term mortality. As the proportion of men increases, BITA grafting is more beneficial in reducing mortality.