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

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.