Duplex scan characteristics of bypass grafts to mesenteric arteries

Background: Mesenteric bypass grafts may be followed postoperatively with duplex scanning. It is unknown, however, if duplex-derived velocity measurements vary over time or if the type of procedure (antegrade vs retrograde) and the caliber of graft affect velocity measurements. The purpose of this study was to characterize duplex findings in mesenteric bypass grafts with respect to the type of revascularization, graft caliber, and changes over time. This study also sought to identify duplex characteristics that could predict subsequent graft failure. Methods: Duplex examinations of mesenteric bypass grafts were reviewed. Peak systolic velocities (PSV) from the inflow artery, proximal anastomosis, mid graft, distal anastomosis, and outflow arteries were analyzed with respect to timing of the examination (index study vs follow-up exam), inflow source, distal target, and graft diameter. The results were compared with analysis of variance (P < .05). Univariate and multivariate analyses were used to determine any association with mid-graft PSV. Results: Fasting postoperative duplex scans were reviewed from 43 mesenteric bypass grafts in 38 patients (28 superior mesenteric artery [SMA] alone, 3 celiac alone, 5 celiac and SMA, 2 SMA and renal). A total of 167 duplex exams were analyzed (mean of 4.5 studies per patient; range, 1 to 14). Inflow artery velocities were significantly lower in antegrade vs retrograde configurations (93 ± 73 cm/s vs 154 ± 73 cm/s, P < .05); however, proximal and mid-graft PSVs were not significantly different between the two groups. In addition, no effect was noted on mid-graft PSV when distal targets were compared (SMA vs celiac, 149 ± 42 cm/s vs 160 ± 78 cm/s, P = NS). An association between smaller graft diameter and higher mid-graft PSV was seen with univariate analysis (P = .03), with a trend toward significance with multivariate analysis (P = .06). In 18 bypass grafts where a follow-up examination was available >1 year (mean 38 ± 25 months) after the index postoperative exam, velocity did not significantly change over time. No duplex scan characteristics were predictive of graft thrombosis. Conclusion: This is the first study, to our knowledge, to fully characterize duplex-derived flow velocities in mesenteric artery bypass grafts. Although surveillance duplex scans after mesenteric bypass procedures may be affected by graft diameter, they are not significantly affected by the choice of inflow artery. These data can serve as standards for postoperative surveillance of mesenteric bypass grafts.