Usefulness of Peak-to-Peak Pulsatility Index in Infrainguinal Bypass Graft Surveillance

Purpose. We conducted this study to find out whether the peak-to-peak pulsatility index (PPI) predicted graft failure and which factors affected the PPI.Methods. Color-duplex sonography was used to take 520 scans of 74 infrainguinal bypasses, 62 of which were femoropopliteal bypasses and 12 of which were femorocrural bypasses. Vessel diameter and velocity waveform were measured in the graft as well as in the proximal and distal arteries.Results. There were 13 cases of graft failure. The PPI in the mid-graft was significantly different in the normal group (12.30 ± 8.77) and the graft failure group (4.17 ± 1.79). A PPI of less than 7.0 in the mid-graft was defined as graft failure, with a sensitivity of 96.0% and a specificity of 77.6%. There was no correlation between the graft diameter and the PPI. The average mode frequency was inversely correlated with the PPI (PPI = 44.8 × Mode F^–1 + 3.50, correlation co-efficient: 0.78).Conclusion. One point measurement of the PPI in the mid-graft could be a simple and useful parameter for diagnosing graft failure, based on our finding that the waveform was very similar in the proximal artery, the entire graft, and the distal artery. PPI was inversely correlated with average mode frequency because reverse flow decreased or diminished when a significant stenosis existed.