Viability of the vertical rectus abdominis musculocutaneous flap in the rat following prior internal mammary artery ligation

Abstract

A large abdominal skin flap nourished superiorly by a single rectus abdominis muscle has well known advantages for providing vascularized tissue coverage of thoracic defects. Unfortunately, if both internal mammary arteries have previously been violated, as is increasingly common today following coronary artery revascularization, initial consideration of this flap would seem to be contraindicated. Nevertheless, anecdotal examples of clinical survival of the rectus abdominis muscle flap in this situation exist. This laboratory study was initiated to ascertain whether a musculocutaneous flap could also be expected to survive. Using a Sprague-Dawley rat model, identical bilateral vertical rectus abdominis musculocutaneous (VRAM) flaps were designed. The internal thoracic [sic. mammary] vessels supplying one muscle had been divided two weeks previously just above the costal margin, as frequently encountered in the clinical situation. Mean survival of control flaps (intact internal thoracic) was 85.5±5.9% versus 67.9±35.3% for the delayed flap that relied on collateral circulation for any viability. Although no statistical difference per se existed between these groups (p=0.32), the great variability in surviving portions of those flaps dependent only on available collaterals suggests extreme caution before assuming that any abdominal skin flap based on a rectus abdominis muscle without an intact internal mammary source vessel would be reliable.