The predictive value of blood flow velocity in femoro-distal bypass

The predictive value of peroperative blood flow measurements has been evaluated in a prospective study of femoro-distal bypass grafts. Seventy grafts placed in patients with critical ischaemia were assessed with a minimum follow-up of 2 years. Thirty-one grafts were performed using autogenous saphenous vein (ASV), 27 using a polytetrafluoroethylene prosthesis (PTFE) and in 12 human umbilical vein (HUV) was used. Six grafts failed early (within 1 month of operation) and 19 failed late, giving an overall patency rate of 60% at 5 years. ASV grafts had a significantly better patency rate than either prosthetic material. Analysis of flow rates measured before and after regional vasodilatation revealed no significant differences between types of graft or between grafts that subsequently failed and those remaining patent. Flow velocity prior to vasodilatation was significantly higher in patent grafts (mean 13.6) compared to those failing early (mean 6.3), but not compared to those failing late (mean 9.4). Flow velocities were also significantly higher in ASV grafts than prosthetic grafts. Flow velocity measured after vasodilatation was significantly higher in grafts remaining patent (mean 28.4) than those which failed late (mean 19.2). It is concluded that flow velocity is of value in the prediction of graft outcome. Graft velocity after vasodilatation of less than 20 cm/s. Predicted failure in 19 of 25 grafts that occluded. We are currently evaluating the selective use of anticoagulants in femoropopliteal grafts with a maximal flow velocity below 20 cm/s.