A meta-analysis comparing bilateral internal mammary artery with left internal mammary artery for coronary artery bypass grafting

Abstract

Background: Increasing evidence continues to demonstrate a survival advantage for bilateral internal mammary artery (BIMA) over left internal mammary artery (LIMA) for coronary artery bypass grafting (CABG). We performed an updated meta-analysis of published studies comparing BIMA versus LIMA in CABG operations and assessed differences in long-term survival.

Methods: Electronic searches for studies comparing BIMA versus LIMA were performed using three databases from 1972 to December 2012. Studies with at least four years of follow-up and at least 100 patients in each group were included for review. We used a random-effect model and pooled hazard ratios from across all included studies.

Results: No randomized controlled trials and 27 observational studies totaling 79,063 patients (19,277 BIMA, 59,786 LIMA) were included for final analysis. The BIMA group demonstrated significantly better long-term survival than the LIMA group [hazard ratio, 0.78; confidence interval, 0.72-0.84; P<0.00001].

Conclusions: In an updated meta-analysis, we demonstrate an increase in long-term survival in patients receiving BIMA as a primary grafting strategy over those receiving a LIMA. Although no randomized controlled trials were included in this meta-analysis, the survival benefit seen with a BIMA cannot be overlooked when determining which operation to perform in CABG patients. Until the long-term results of the ART trial are published, we offer best available evidence in favor of BIMA over LIMA for CABG surgery.

Keywords: Internal mammary artery; bilateral; coronary artery bypass; meta-analysis.

Figure 1

Illustration of bilateral internal mammary artery grafts. RIMA, right internal mammary artery; LIMA, left internal mammary artery; LAD, left anterior descending artery; PDA, posterior descending artery; Cx, circumflex; RA, radial artery

Figure 2

Flowchart of the method for selecting the studies included in the meta-analysis (MA)

Figure 3

Forest plot of the hazard ratio (HR) of survival in BIMA versus LIMA studies. The estimate of the HR of each trial corresponds to the middle of the squares, and the horizontal line shows the 95% confidence interval (CI). On each line, the inverse variance and study size is shown. The sum of the statistics is represented by the middle of the solid diamond. A test of heterogeneity between the trials within a subgroup is given below the summary statistics. IV, inverse variance; BIMA, bilateral internal mammary artery; LIMA, left internal mammary artery

Figure 4

Funnel plot for the meta-analysis of mortality comparing BIMA versus LIMA in all 27 included studies. The log of hazard ratio (HR) comparing mortality (vertical axis) is presented against the standard error (SE) of the log of HR (horizontal axis). The SE inversely corresponds to the study size. Asymmetry of the plot can indicate publication bias. BIMA, bilateral internal mammary artery; LIMA, left internal mammary artery