Single vs Bilateral Internal Mammary Artery Grafts in CABG.
The left internal mammary artery (LIMA) graft to the left anterior descending (LAD) artery is the single most important component of coronary artery bypass surgery, with 10-year patency rates exceeding 90%. The question of whether using both internal mammary arteries (bilateral IMA or BIMA) provides an additional survival advantage has been debated for decades. Large observational studies have consistently shown a survival benefit with BIMA grafting, particularly in younger patients. However, the landmark ART trial — the only large randomized trial on this question — showed no survival difference at 10 years, creating uncertainty. BIMA grafting also carries a higher risk of deep sternal wound infection due to devascularization of the sternum from both sides, particularly in obese and diabetic patients. The debate centers on patient selection, surgical technique (skeletonization to preserve sternal blood supply), and whether the long-term patency advantage of a second arterial graft translates to meaningful clinical benefit.
Head-to-head comparison.
Single IMA (SIMA)
The standard CABG approach uses the left internal mammary artery (LIMA) as an in situ graft to the LAD, with saphenous vein grafts (SVG) to remaining targets. This is the most widely performed configuration worldwide, with excellent long-term outcomes. The LIMA-LAD graft provides the survival benefit of arterial grafting to the most important coronary territory.
Bilateral IMA (BIMA)
BIMA grafting uses both the left and right internal mammary arteries as conduits, maximizing arterial revascularization. The LIMA typically grafts the LAD, while the RIMA is directed to the second most important target (circumflex territory or diagonal). Various configurations exist: in situ BIMA, composite Y-grafts, and free RIMA grafts. Skeletonized harvesting preserves sternal blood supply and reduces wound complications.
Key clinical trials.
What the guidelines say.
The 2021 ACC/AHA Guidelines recommend LIMA-to-LAD grafting for all CABG patients (Class I). BIMA grafting is reasonable in patients who are not at elevated risk for sternal complications (Class IIa), particularly when performed with skeletonized harvesting technique. The guidelines note that BIMA should be used cautiously in obese and diabetic patients due to higher sternal wound infection risk. The ESC 2024 Guidelines similarly support BIMA in appropriate candidates, emphasizing skeletonization.
Why the Heart Team matters.
The BIMA decision requires the surgeon to weigh the potential long-term graft patency benefit against the risk of sternal wound complications for each individual patient. Patient factors such as BMI, diabetes control, bilateral mammary artery anatomy, and life expectancy all influence the decision. The cardiologist provides coronary anatomy assessment including the importance of non-LAD targets. WhiteGloveMD provides a second surgical perspective on whether BIMA grafting is appropriate and whether skeletonized harvesting would mitigate sternal wound risk.
BIMA grafting may offer a long-term survival advantage based on observational data, but the ART trial — the only large RCT — did not confirm this benefit. SIMA with LIMA-to-LAD remains an excellent standard approach. BIMA is most beneficial in younger, non-diabetic patients with a long life expectancy, performed by surgeons experienced in skeletonized harvesting. The decision should be individualized based on patient risk factors, not applied as a universal strategy.
Frequently asked questions.
Should I ask my surgeon for bilateral mammary grafts?
BIMA grafting is reasonable for younger, non-obese, non-diabetic patients undergoing CABG. Ask your surgeon about their experience with BIMA, their skeletonized harvesting technique, and their personal sternal wound complication rates. Not all patients benefit from BIMA, and surgeon experience is critical.
What is skeletonized harvesting?
Skeletonization means harvesting only the artery itself, leaving the surrounding tissue (pedicle) intact to preserve sternal blood supply. This technique significantly reduces deep sternal wound infection risk with BIMA (from 3-5% to 1-2%) and is considered essential for safe bilateral mammary grafting.
Does the ART trial mean BIMA is not beneficial?
The ART trial had significant limitations: a 40% crossover rate (patients randomized to BIMA who received only SIMA) diluted the treatment effect. Many experts believe the observational data showing BIMA benefit is valid, and that the ART trial was underpowered due to crossover. The question remains genuinely unresolved.
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