Predicting Internal Mammary Artery Graft Failure
What are the frequency, predictors, and impact of internal mammary artery (IMA) graft failure in patients undergoing coronary artery bypass grafting (CABG)?
This was a post hoc analysis of the PREVENT IV (PRoject of Ex-Vivo vein graft ENgineering via Transfection) trial, which was a double-blind, multicenter, randomized clinical trial in which edifoligide (a E2F transcription factor decoy) was compared with placebo in ex vivo treatment of vein grafts during coronary artery bypass grafting (CABG). The primary outcome was IMA graft failure, defined as stenosis of at least 75% or occlusion of the diameter of the lumen of the IMA graft, which was assessed by quantitative coronary angiography 12-18 months after surgery, or earlier when performed as part of medical care and IMA graft failure was found.
The analytic sample included 1,539 participants. IMA graft failure occurred in 132 participants (8.6%) at angiographic follow-up. Predictors of IMA graft failure were left anterior descending (LAD) stenosis <75% (odds ratio [OR], 1.76; 95% confidence interval [CI], 1.19-2.59), additional bypass graft to diagonal branch (OR, 1.92; 95% CI, 1.33-2.76), and not having diabetes (OR, 1.82; 95% CI, 1.20-2.78).
IMA failure occurred in 8.6% of participants. Independent predictors of IMA failure were angiographically intermediate LAD stenosis and additional bypass graft to the diagonal branch.
This is a valuable study that draws attention to the predictors of IMA failure following CABG. Most notably, the authors corroborate others’ findings by demonstrating that less severe preoperative LAD stenosis is a predictor of IMA graft failure. The authors opine: “The decision to use an IMA should be carefully considered in light of the severity of the stenosis of the target vessel,” and that “one should also take into account the risk of introducing ‘competitive flow’ when placing an additional bypass graft to the diagonal branch of the LAD.”
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