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Second Arterial Conduits for CABG
Study Questions:
Is the use of a second arterial conduit during coronary artery bypass grafting (CABG) associated with better outcomes?
Methods:
The authors analyzed a statewide clinical registry of CABG in 126 hospitals. Outcomes of interest were all-cause mortality and a composite of major adverse cardiovascular and cerebrovascular events (MACCE) including stroke, myocardial infarction, and repeat revascularization. Sternal wound infections were also evaluated. Propensity score techniques were used to match cohorts who underwent CABG using the left internal mammary artery (LIMA) and a second arterial conduit (right internal mammary artery [RIMA] or radial artery) compared to venous conduits. Only patients who underwent primary, isolated multivessel CABG were included. An instrumental variable approach was used as a sensitivity analysis. A subgroup analysis comparing RIMA versus radial artery was also performed.
Results:
There were 5,866 patients who underwent CABG with a second arterial conduit compared to 53,566 who underwent CABG with LIMA and venous conduits. After matching, there were 5,813 pairs. Median follow-up time was 5.3 years (interquartile range, 3.8-6.7 years). Thirty-day mortality was not different between groups (0.81% vs. 0.86%). However, 7-year mortality was significantly lower when a second arterial conduit was used (10.6% vs. 13.1%, hazard ratio [HR], 0.79; p < 0.0001). MACCE was significantly lower when a second arterial conduit was used (31.0% vs. 36.2%, HR, 0.80; p < 0.0001). No differences were seen in rates of sternal wound infections at 1 year (1.38% with second arterial conduit vs. 1.44%). There was no difference in mortality between RIMA and radial artery grafting. However, after comprehensive adjustment, including for surgeon-specific effects, RIMA grafting was associated with increased MACCE (HR, 1.12). RIMA grafting was also associated with increased rates of sternal wound infections (2.29% vs. 1.22%).
Conclusions:
Although only a small proportion of CABG patients received a second arterial conduit, use of a second arterial conduit was associated with lower mortality and less MACCE. Importantly, the radial artery appeared to be equivalent to the RIMA from the perspective of mortality and superior from the perspective of MACCE and sternal wound infections.
Perspective:
This is a very large study, which adds to the body of observational data supporting the use of second arterial grafts during CABG. These data contrast with the ART trial, which showed no difference in outcomes between LIMA versus bilateral internal mammary graft use during CABG. In part, this discrepancy could have been due to differences in outcomes between the use of RIMA and the radial artery as well as crossing over from assigned surgical strategy. This divergence between observational and randomized trials poses significant dilemmas for clinicians. In particular, remaining uncertainty over implications of radial artery use during CABG warrants further investigation.
Keywords: Cardiac Surgical Procedures, Coronary Artery Bypass, Mammary Arteries, Myocardial Infarction, Myocardial Ischemia, Radial Artery, Stroke, Surgeons, Treatment Outcome, Wound Infection, Angina, Stable
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