Contraindications to Bilateral Internal Mammary Artery (BIMA) Grafting
While BIMA grafting provides superior long-term survival compared to single IMA grafting, the primary contraindication is diabetes mellitus combined with obesity due to significantly elevated risk of deep sternal wound infection, which can reach 22.2% in diabetic patients receiving BIMA grafts. 1, 2
Absolute and Relative Contraindications
High-Risk Patient Populations
Diabetes Mellitus:
- Diabetic patients face a 22.2% risk of deep sternal wound infection with BIMA grafting compared to 4.6% with alternative conduits 2
- The combination of diabetes and bilateral IMA use is independently associated with significantly higher sternal infection rates (p < 0.05) 1
- However, skeletonized harvesting technique can substantially mitigate this risk, making BIMA feasible even in diabetics when performed by experienced surgeons 3, 4
Obesity:
- Obesity is independently associated with increased sternal wound complications in BIMA patients (p < 0.05) 1
- The combination of obesity and diabetes creates particularly high risk 1
- Despite concerns, recent evidence suggests skeletonized BIMA harvesting does not significantly increase sternal complications even in obese patients 3
Need for Prolonged Mechanical Ventilation:
- Patients requiring >48 hours of postoperative mechanical ventilation have significantly higher sternal infection rates with BIMA grafting (p < 0.05) 1
Clinical Situations Favoring Alternative Conduits
Chronic Kidney Disease:
- Avoid BIMA in patients with high likelihood of rapid progression to hemodialysis to preserve at least one internal mammary artery and both radial arteries for future dialysis access 5, 6
Emergency or Urgent Surgery:
- BIMA patients historically underwent fewer emergent or urgent procedures, suggesting surgeon selection against BIMA in unstable patients 1
Poor Cardiac Function:
- Patients with severely compromised left ventricular function may not tolerate the additional operative time required for BIMA harvesting 1
Combined Cardiac Procedures:
- BIMA grafting is performed less frequently when CABG is combined with other cardiac operations due to increased complexity and operative time 1
Technical Contraindications
Posterior Descending Artery as Target:
- The right IMA has significantly higher failure rates when used as a pedicled graft to the posterior descending artery, with 4.4% requiring reoperation for graft failure within 12 months 2
- In this anatomic scenario, alternative conduits (right gastroepiploic artery or radial artery) are preferred 2
Inadequate IMA Length or Quality:
- When the right IMA is unavailable or unsuitable, alternative arterial conduits should be used rather than forcing BIMA grafting 5
Risk Mitigation Strategies When BIMA is Considered
Harvesting Technique:
- Use skeletonized harvesting technique rather than pedicled harvesting to reduce sternal devascularization and wound complications 5, 3, 4
- This technique is particularly important in diabetic and obese patients 3
Patient Selection Algorithm:
- Young patients (≤60 years) with few comorbidities are ideal BIMA candidates 5, 7
- BIMA should be strongly considered when performed by experienced surgeons in appropriate patients 7
- The survival advantage of BIMA increases with time from surgery, making it particularly valuable in younger patients 4
Common Pitfalls to Avoid
- Do not assume all diabetic or obese patients are automatically excluded from BIMA grafting—skeletonized technique substantially reduces risk 3
- Recognize that sternal wound infection rates with BIMA (6.9%) are significantly higher than single IMA (1.9%) or vein grafts (1.3%) in unselected populations 1
- Avoid BIMA when the posterior descending artery is the primary right-sided target—use alternative conduits 2
- Consider that only 4% of US CABG procedures use BIMA despite proven long-term benefits, suggesting many appropriate candidates are not receiving optimal grafting 5