Follow-up
Postoperative management was in accordance with hospital protocols. Participants were followed up at 3 and 12 months by questionnaire to assess wound infection, leg wound pain and dysesthesia, and readmissions to hospital; and attended hospital for IVUS and angiographic imaging at 12 months.

Statistical Methods

Analyses were based on a pre-specified statistical analysis plan, were performed on an intention-to-treat basis and are reported in line with the CONSORT reporting guidelines. Patient level means of the multiple IVUS measurements per graft were calculated for wall thickness, lumen diameter, lumen area and wall area. Binary outcomes were compared using logistic regression, counts using Poisson regression, time to event outcomes using Cox proportional hazards models and continuous longitudinal outcomes using hierarchical mixed effects models, to account for participants with multiple grafts and IVUS frames of each graft. Analyses were adjusted for IVUS frame number as a continuous fixed covariate and patient and graft number as random effects. Multiple imputation by predictive mean matching using chained equations was used to impute missing data for the primary outcomes and angiographic assessment of lumen diameter. Data missing due to graft occlusion was not imputed. See Appendix for further details. All analyses used the conventional harvest and high pressure as the reference groups and included harvest technique, pressure test and the interaction between two (if significant at the 10% level) and were adjusted for baseline measurements where available. If a significant interaction is indicated, pressure testing is compared and reported for each harvest technique separately (and harvest technique is compared and reported for each pressure test separately) otherwise the main effects of harvest technique and pressure test are reported. There was no adjustment for multiple comparisons. All analyses were performed in Stata version 14.0 (StataCorp LP, College Station, Tex) and SAS version 9.4 (SAS Institute Inc, Cary, NC).