Early duplex-derived hemodynamic parameters after lower extremity bypass in diabetics: implications for mid-term...

Early postoperative changes in the hemodynamic parameters of infrainguinal bypass grafts in diabetics have not been well defined. We undertook this study to better define such changes in duplex-derived velocities and waveforms, and correlate any observed changes with intermediate-term outcomes. A prospective study of 68 primary vein bypasses for limb salvage was carried out, with scans obtained intraoperatively, daily until discharge, and at 8- to 12-weeks intervals. During follow-up (12 +/- 6 months), 20 grafts developed stenoses, 17 occluded, and 8 limbs were amputated. Most grafts show a variant of a biphasic waveform intraoperatively at the mid-graft (MG) and distal graft (DG) levels (54% and 57%); 65% of waveforms remain unchanged during the first week, and 54% remain unchanged at 3 months. No duplex-derived factors were predictive of the development of stenoses. A number of parameters were predictive of ultimate graft thrombosis. Intraoperative MG velocity was higher in grafts that eventually remained patent (83 +/- 36 vs. 60 +/- 29 cm/sec; p <0.025). Grafts that remained patent also had a much lower decline in DG and distal native (DN) velocities from immediately postoperative to 8-12 weeks later, than grafts that eventually thrombosed (-3 +/- 35 vs. -44 +/- 43 cm/sec for DG, p <0.001; and -17 +/- 66 vs. -76 +/- 53 cm/sec for DN, p <0.04 respectively). In terms of limb salvage, when the MG or DG waveform worsened (from postoperation to 12 weeks later), amputation was more likely than when it remained unchanged or improved (MG 67% vs. 9% limb loss, p <0.04; DG 43% vs. 8% limb loss, p <0.04). We conclude that intensive graft duplex surveillance does not identify grafts likely to develop stenoses. However, a number of features allow the prediction of ultimate graft failure or limb loss.