Comparison of patency rate and structural changes of in Situ and reversed vein arterial bypass

We hypothesize that in situ vein may be a better arterial conduit than reversed vein. In order to evaluate this hypothesis, 47 in situ and 22 reversed vein bypasses from femoral to below knee arterial reconstructions were done for limb salvage and followed at 3-month intervals up to 30 months. Patients' age, sex, and run-off were similar in both groups. The cumulative patency rates at 12 and 30 months were 95 and 92% for the in situ group in contrast to 63 and 63% for the reversed group. These differences were significant (P < 0.01). This study was begun in a randomized manner, however, in situ vein bypass became the preferred procedure in the later part of the study. We further investigated the structural changes of in situ and reversed vein bypass in eight dogs. The left carotid artery was bypassed using in situ external jugular vein (ISV) and the right carotid artery was bypassed with reversed external jugular vein (RV) in each dog. These veins were examined by light and electron microscopy (scanning and transmission) prior to and at 1, 4, 8, 16, and 24 weeks following arterialization. At each interval RV showed endothelial disruption, degenerative changes, and progressive structural abnormalities similar to those of early atherosclerosis. In contrast, ISV showed minimal degenerative change, and underwent smooth transformation into a histologically appearing normal artery. This difference suggests that ischemia of the venous wall of RV may be responsible for the structural changes. The improved clinical patency rates seen with the in situ bypass may be explained by these experimental data.