Rat Epigastric Flow-Through Flap as a Modulated Arteriovenous Fistula: Model for the Radial Artery Flow-Through Flap in Distal Arterial Bypass

ABSTRACT The authors describe a rat flap model that is useful for flow studies. It is an epigastric flow-through flap that mimics the clinical use of a radial artery flow-through (RAFT) flap that has been used as an adjunct to a distal lower extremity arterial bypass graft to improve patency when there is potential high outflow resistance. The hypotheses were that this RAFT flap serves two purposes: 1) it allows additional blood flow through the skin flap and drainage via the vena comitans to increase the blood flow through the bypass graft and help to maintain bypass graft patency; and 2) it acts as a modulating arteriovenous fistula in which the additional flow through the vena comitans of the flow-through flap fluctuates with distal arterial outflow resistance. The rat epigastric flow-through flap model was designed to test these hypotheses. High outflow resistance was induced by sequentially ligating the outflow vessels of the rat femoral artery. Using this model, an increase in blood flow to the skin via the epigastric artery of the flow-through flap was demonstrated as outflow obstruction increased. Then, the patency rates of the flow-through flap bypass were compared to an interpositional arterial graft. The flow-through flap maintained patency while the arterial interposition bypass thrombosed, with near total outflow obstruction induced by serial ligation of the outflow vessels (75 percent patent anastomoses at 1 week for flow-through flap vs. 0 percent for the arterial graft). This flow study demonstrates the inherent ability of the flow-through flap to divert blood flow through the skin capillaries when there is high arterial outflow resistance. The authors believe that a flow-through flap such as the RAFT flap can be an important adjunct to the traditional distal arterial bypass in a subset of patients with high outflow resistance in the recipient artery.