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).