VIABILITY OF THE VERTICAL RECTUS-ABDOMINIS MUSCULOCUTANEONS FLAP IN THE RAT FOLLOWING PRIOR INTERNAL MAMMARY ARTERY LIGATION

A large abdominal skin flap nourished superiorly by a single rectus ab dominis muscle has well known advantages for providing vascularized ti ssue coverage of thoracic defects. Unfortunately, if both internal mam mary arteries have previously been violated, as is increasingly common today following coronary artery revascularization, initial considerat ion of this flap would seem to be contraindicated. Nevertheless, anecd otal examples of clinical survival of the rectus abdominis muscle flap in this situation exist. This laboratory study was initiated to ascer tain whether a musculocutaneous flap could also be expected to survive . Using a Sprague-Dawley rat model, identical bilateral vertical rectu s abdominis musculocutaneous (VRAM) flaps were designed. The internal thoracic [sie. mammary] vessels supplying one muscle had been divided two weeks previously just above the costal margin, as frequently encou ntered in the clinical situation. Mean survival of control flaps (inta ct internal thoracic) was 85.5+/-5.9% versus 67.9+/-35.3% for the dela yed flap that relied on collateral circulation for any viability. Alth ough no statistical difference per se existed between these groups (p= 0.32), the great variability in surviving portions of those flaps depe ndent only on available collaterals suggests extreme caution before as suming that any abdominal skin flap based on a rectus abdominis muscle without an intact internal mammary source vessel would be reliable.