The inherent limitations of sequential arterial bypass grafts: a hemodynamic study

While proximal bypass graft flows are known to increase by the sequential technique, the possibility of a "steal phenomenon" caused by the intermediate anastomosis has been raised. We compared graft and distal flow rates using simple reversed vein versus sequential bypass grafts in a canine model. A blind segment was created by occluding the common iliac artery above and the superficial femoral artery below a profunda femoris artery equivalent, which served as runoff from the blind segment. Reversed saphenous vein harvested from the contralateral thigh in seven anesthetized dogs was used to perform a simple common iliac artery to superficial femoral artery bypass. Graft and distal superficial femoral artery flow were measured with a calibrated flow probe of appropriate diameter (3-5 mm). A sequential side-to-side vein graft to arterial blind segment anastomosis was then added and flow measurements repeated after equilibration. Mean graft flow increased by 20 cc/min with the sequential technique (p = 0.05), while distal flow actually decreased by 1 cc/min (NS). Although no "steal phenomenon" was demonstrated, distal flow was not significantly improved by the sequential technique. We conclude that no convincing case based on presumed hemodynamic superiority can be made for performing sequential bypass in preference to standard reversed vein bypass. The increased potential for technical error introduced by the additional anastomosis and the lack of any demonstrable augmentation in distal flow suggest inherent limitations of the technique, and caution against its widespread use.