RESULTS

Recruitment

Trial recruitment was from December 2009 until October 2013. A total of 712 patients were assessed for eligibility. Of 195 patients who were approached, 109 consented, and 97 were randomised into the trial. Overall, 46 patients were allocated to receive conventional harvest, and 51 to receive pedicled harvest; 49 to receive low pressure, and 48 to receive high pressure (Figure 1 ).
The primary analysis included 96 randomised patients, excluding one patient who was withdrawn during surgery as no vein grafts were harvested. Protocol deviations occurred in 37 grafts from 21 patients (Table 1 , Appendix Table A1 ). In total, 17 patients randomised to pedicled harvest received conventional harvest, 6 patients randomised to low-pressure received high-pressure. Unblinding of treatment allocation occurred for one patient randomised to the pedicled harvest and high-pressure group.
A total of 20 of the 96 patients did not attend for the 12-month IVUS and angiography assessment, 12 of whom returned at least one questionnaire at 12 months. Seventeen patients formally withdrew from the trial, 15 from 12-month IVUS and angiography assessment only and 2 from all follow-up (Figure 1 , Appendix Table A2) .

Baseline data

The mean age of participants was 66.0 years (SD 8.9), and 87/96 (91%) were male. By chance, patients randomised to pedicled harvest were slightly older than those randomised to the conventional harvest group (mean 67.3 years vs. 64.5 years), and the low-pressure group had proportionally more males than the high-pressure group (96% vs. 85%). From histology of veins after surgical preparation, the median wall thickness was greater in the low-pressure (0.39 vs. 0.32mm) and pedicled harvest (0.39 vs. 0.31mm) groups and the median lumen diameter was smaller in these groups (pressure comparison 2.87 vs. 3.30mm; harvest comparison 2.87 vs. 3.35mm) (Table 2, Appendix Table A3 ).

Operative details

The median duration of surgery was 3 hours and was similar across groups. Overall, 28/96 (29%) procedures were performed on-pump. Study participants received a total of 275 grafts (mean 2.9 grafts per patient), of which 160 (58%) were vein grafts. The most common vein graft sites were RCA-PDA (n=50, 31%), Diag (n=21, 13%), OM1 (n=39, 24%) and OM2 (n=19, 12%), while the majority of arterial grafts were LAD (n=90, 80%). Most vein graft conduits were judged good quality (n=90, 56%), with a higher proportion of good quality conduits in the conventional harvest group compared to the pedicled harvest group (61% vs. 52%). Most vein grafts were taken from the left leg long saphenous vein (n=132, 83%, Table 3, Appendix Tables A4 and A5 ).

Primary Outcomes at 12 months