Doppler spectral characteristics of infrainguinal vein bypasses

With the aim of assessing the velocity profile of femoropopliteal and femorocrural vein bypasses, 128 patients undergoing infrainguinal vein bypass surgery entered a postoperative Duplex surveillance protocol, which included clinical assessment and Duplex scanning, using Doppler spectral analysis. Doppler spectra were obtained at three sites in each graft and the following waveform parameters recorded: maximum systolic velocity, minimum diastolic velocity and resistance index. In patent reconstructions systolic velocity decreased by 30% during the first 6 months after surgery. In the absence of arteriovenous fistulas the initially antegrade diastolic velocity was replaced by a retrograde flow within 3 months, whereas a forward flow in diastole was sustained in grafts with patent fistulas. Abnormal Duplex findings in 31 patients led to angiography and revision in 13 cases. Four revised grafts failed, while nine remained patent at follow-up 1-12 months later. Ten (56%) of 18 non-revised bypasses with abnormal Duplex findings failed within 9 months compared to 1 (1%) of 76 bypasses with a normal velocity profile (p < 0.00001). In conclusion, Ultrasound Duplex scanning with spectral analysis provides valuable information concerning haemodynamics of infrainguinal vein bypasses and identifies grafts at risk of thrombosis. Inclusion of low resistance index (< 0.75) as an additional criteria for detection of stenoses appears to improve the sensitivity of Duplex scanning.