Relationship between flow and incidence of thrombosis in polytetrafluoroethylene vascular grafts in free microvascular flaps in lambs

Abstract

We have done an experimental study inlambs in which we investigated the influence of flowrate on free microvascular flaps using polytetrafluoroethylene (PTFE) vascular grafts. We set up fivesurgical groups in which blood flow was progressively increased through the PTFE vascular graft. Ingroup I (venous autograft) we observed just onevascular thrombosis which was located at the site ofthe anastomosis. In group II (PTFE 3-10 mm) allthe microvascular flaps became necrosed after thethird postoperative day. In group III (PTFE 310 mm) necrosis also developed in all cases, but theanastomoses remained permeable no longer thaneight days. In group IV (3 15 mm) the permeabilityin the microvascular free flaps was about 40% after 21days, and in group V (3 10 mm) it reached 70%. Tomatch graft flow rates with flap survival we did aregression analysis of flow rates for groups II, III, andV and the corresponding survival periods for the flaps.There was a clear and highly significant relationship(r = 0.717, p = 0.0001). In conclusion, it is necessaryto maintain blood flow through the prosthesis at a ratehigher than the thrombogenic threshold. When theflow rate in the vessels through the PTFE grafts washigher, the viability of the flaps was better. The idealsurgical technique should always be based on anarteriovenous fistula distal to the PTFE vascular graft.It is necessary to maintain blood flow through aprosthesis at a rate higher than the thrombogenicthreshold.