Venous interruption is unnecessary to achieve an adequate delay in the rat TRAM flap model

Staged division of any or all inferior dominant pedicles to the human lower transverse rectus abdominis musculocutaneous (TRAM) flap has previously been attempted to invoke the delay phenomenon to enhance the rate of success with the superior-pedicled version, especially for patients at high risk for complications. Regardless of the specific vessels ligated, this has usually been accomplished by division of the source artery and its accompanying vein. Whether division of both vessels is essential remains unclear, however. This issue was investigated by using the authors' standard rat TRAM flap model in 43 female Sprague-Dawley rats, which were randomly assigned to four groups. In group A, both the predominant ipsilateral cranial epigastric artery and the cranial epigastric vein were divided 2 weeks before elevation of the TRAM flap. In group B, only the artery was divided; in group C, only the vein was divided. In an undelayed control group, the TRAM flap was elevated immediately, with no prior pedicle division. The percentages of flap survival in group A (89.3 +/- 7.0 percent) and group B (88.8 +/- 6.5 percent) (both with division of the predominant artery) were significantly greater than that in the control group (64.6 +/- 20.5 percent) (p < 0.001) or that in the group in which the vein alone was divided (73.9 +/- 11.3 percent) (p < 0.01). There was no significant difference between the group that underwent vein division only and the control group (p = 0.102). The clinical implication is that arterial division is critical for TRAM flap delay and that arbitrary venous interruption is unnecessary.