Pressure traps in femoro-popliteal reversed vein grafts. Are valves culprits?

Background Stenosis is a major cause of vein graft failure In peripheral ar terial surgery, Our goal is to determine whether vein valves play a role in this process by creating a "pressure trap". Methods. Seventeen patients with femoro-popliteal reversed saphenous vein g rafts were studied intraoperatively. Flow and pressure in the grafts were m easured, while the graft outflow was gradually occluded and released for 2- 4 seconds, In 3 patients the graft now was reduced by compressing calf musc les. Results. Patients heart rates were 54-84 BPM, blood pressures 170/80-110/55 mmHg, and normal graft flow was 40-180 ml/min. In 12 patients with compete nt vein valves, at reduced flow (< 30 ml/min) the valves opened and closed in each cardiac cycle. At each closure the pressure was "trapped" distal to the valve producing diastolic hypertension. Also the flow was stagnant for a considerable portion of the cardiac cycle. Maximum diastolic pressure gr adient across the valve ranged from 35 to 60 mmHg and the level of pressure trapped was inversely proportional to the graft flow. Conclusions. In patients in whom reversed vein grafts with competent valves are placed in the femoro-popliteal positions a "pressure-trap" develops in the distal segment. This segmental hypertension combined with the flow sta gnation could play an important role in the graft thickening and stenosis.