Sternal neoangiogenesis following internal mammary artery devascularization: an experimental model

The use of bilateral internal thoracic arteries (BIMA) for coronary artery revascularization is associated with better long-term survival and longer freedom from reoperation. Concerns of deep sternal wound infections and mediastinitis have constantly emerged with the utilization of BIMA grafts on a routine basis, especially in diabetic patients.

We performed a quantitative evaluation of sternal bone healing and angiogenesis after left (LIMA) or bilateral internal mammary artery (BIMA) ligation two and four weeks after sternotomy in normal and diabetic Sprague-Dawley rats.

The BIMA group showed a significant increase in neoangiogenesis two weeks after surgery compared to LIMA and control groups (control: 38.3 ± 5.1 vessels/mm², LIMA: 31.4 ± 3.6 vessels/mm², BIMA: 81.6 ± 7.7 vessels/mm²; P=0.047 and P=0.04, respectively). Four weeks after the procedure, bilateral devascularization was associated with lower microvessel formation when compared to LIMA or control groups (control: 50.4 ± 5.2 vessels/mm², LIMA: 64.6 ± 4.9 vessels/mm²; BIMA: 31.5 ± 4.4 vessels/mm²; P=0.006 and P=0.02, respectively). Diabetic animals showed similar results with lower four weeks microvessel formation. However, there were no significant differences when animals with induced diabetes were compared to the normal euglycemic groups for each procedure performed.

BIMA ligation promotes an early increase in neoangiogenesis. Progressive sternal consolidation is associated with a significant lower level of capillaries and arterioles in the BIMA group four weeks after ligation. Diabetes did not influence the extent of neoangiogenesis between groups with similar procedures. More important clinical determinants could explain the increase incidence of sternal infection in this specific population.