Wall thickness
Grafts assessed using IVUS had, on average, thicker walls than the surgically prepared veins assessed by histology. There was a trend towards a difference in mean wall thickness according to the harvest technique and pressure test used (test for interaction between the pressure test and harvest technique, p=0.070). In patients randomised to conventional harvest, those in the low-pressure group had, on average, a thinner vessel wall compared to those in the high-pressure group (mean difference MD (low minus high) = -0.059mm, 95%CI -0.12, +0.0039, p=0.066). By contrast, in patients randomised to pedicled harvest the wall thickness was similar irrespective of distension pressure (MD (low minus high) = +0.019mm, 95%CI -0.038, +0.075, p=0.51).
Comparing the results by harvest method in patients randomised to a high pressure test, grafts with a pedicle had a thinner vessel wall than those in the conventional harvest group (MD (pedicle minus conventional) = -0.057mm, 95%CI -0.12, +0.0037, p=0.066). For those randomised to a low-pressure test, wall thicknesses were similar for the two harvest techniques (MD (pedicle minus conventional) = +0.021mm, 95%CI -0.038, +0.081, p=0.48, Figure 2, Table 4, Appendix Table A6 ).