The effect of the delay phenomenon on the vascularity of rabbit abdominal cutaneous island flaps.

The beneficial effects of the delay phenomenon have been evaluated extensively and are widely known. However, no study has quantified the vascular changes seen in an abdominal cutaneous island flap following a surgical delay by vascular pedicle ligation. We evaluated the effect of unilateral superficial inferior epigastric and deep inferior epigastric pedicle ligation on the vascularity of a rabbit abdominal cutaneous island flap. Thirty rabbits underwent a left superficial inferior epigastric and deep inferior epigastric pedicle ligation as a delay procedure. A 19 x 15 cm abdominal cutaneous island flap was elevated at the time of sacrifice, based solely on the right superficial inferior epigastric pedicle. The flap vasculature was then evaluated by methylene blue injection and lead oxide microangiography at 0, 5, 10, 15, 21, and 27 days following the delay procedure. Methylene blue studies revealed perfusion of only the right (nonligated) side of the flap on day 0 and perfusion of the entire flap by day 15. This "capture" of the left (ligated) superficial inferior epigastric artery angiosome by day 15 could only have been achieved through enhanced cross-midline perfusion. Lead oxide microangiography revealed an increase in the number of vessels from day 0 to day 27 on both the ligated and nonligated sides in all the following: the number of large "choke" vessels (> 0.5 mm) crossing the flap midline, total number of vessels (all sizes) crossing the flap midline, and total number of vessels (all sizes) at the medial aspect of the right and left superficial inferior epigastric artery angiosomes. A statistically significant increase in these vessels was not seen until day 21. The effect of the delay phenomenon was significantly greater on the ligated side compared with the nonligated side. The areas of the flap that were relatively more ischemic following left superficial inferior epigastric pedicle ligation (medial aspect of the caudad half of the left superficial inferior epigastric artery angiosome) showed greater increases in vascularity with the delay procedure than did areas of lesser ischemia (medial aspect of the cephalad half of the right superficial inferior epigastric artery angiosome).