**6. Incidence of sternal wound infection, subset of patients benefiting from BIMA, IMA harvesting techniques, and operative time in BIMA CABG**

One of the main concerns amongst surgeons regarding the use of BIMA in CABG procedures is the occurrence of sternal wound infections (SWI). When both internal mammary arteries are harvested, blood supply to the sternum may be more severely compromised than in single IMA procedures, thus increasing the risk for developing SWI. Various pre-operative and intraoperative techniques have been used to prevent the incidence of SWI, such as the use of prophylactic antibiotics, double gloving, and skeletonized IMA harvesting [7]. Skeletonized IMA harvesting is thought to preserve the collateral blood supply to the sternum and reduce the risk of infection [22].

Patients who are insulin-dependent diabetics, morbidly obese, or who have severe COPD are at a higher risk of developing SWI (DSWI = deep sternal wound infection, definition varies) and, in general, bilateral harvesting of the IMAs is avoided in these patients [7, 8].

In a study performed by Pevni *et al.*, 1,515 consecutive patients underwent CABG procedures with skeletonized BIMA grafting. In earlier studies, the authors state that, in their past experience, patients with chronic lung disease, diabetic females, and obese diabetics repre‐ sented absolute contraindications to BIMA grafting for CABG procedures because of the risk of SWI. However in this study, the authors found that there was no evidence of a relationship between diabetes mellitus and DSWI in patients receiving skeletonized BIMA grafts, even with a prevalence of diabetes mellitus of 34% in their patient population [23].

In a meta-analysis of 13 studies regarding BIMA CABG procedures and the harvesting technique for the IMAs, Saso *et al.* found that skeletonizing the IMA as opposed to harvesting it in a pedicled manner lowered the incidence of SWI by 60%. An even greater benefit of skeletonized harvesting was noted in groups at an increased risk for SWI, such as in diabetic patients. The authors also found that these decreased rates of SWI applied to the entire spectrum of sternal infections, including mediastinitis [22].

Kurlansky *et al.* found a slightly higher incidence of SWI amongst diabetic patients receiving BIMA grafting compared to diabetic patients receiving LIMA grafting, but the difference was not significant. However, amongst patients receiving BIMA grafts, the presence of diabetes did affect the occurrence of SWI. This suggests that, while the presence of diabetes mellitus could still be considered a risk factor for SWI, the risk is not increased by receiving BIMA grafting [12].

One of the probable factors contributing to the low prevalence of BIMA use is the perceived increased operative time required to harvest both IMAs [7]. However, few studies have actually included operative time in their statistical analyses, most simply report aortic crossclamp and cardiopulmonary bypass times. Gansera *et al.* do report total operative time and found that operative time was significantly increased for patients receiving BIMA grafting compared to patients receiving SIMA grafting (189 minutes versus 164 minutes, respectively, p = 0.00). However, the number of anastomoses in the BIMA group was significantly higher than in the SIMA group (3.8 versus 3.1, respectively, p = 0.00), which could in part explain the increased operative time observed [8].
