A retrospective analysis of a multicenter randomized clinical trial conducted at 18 Veterans Affairs hospitals using the Randomized On/Off Bypass (ROOBY) trial data set examined one-year graft patency and intraoperative revision rates in 1,607 patients undergoing CABG based on intraoperative transit time flow assessment in 2,738 grafts.

Included in the analysis was frequency of flow probe use; intraoperative flow values and pulsatility index (PI) values; intraoperative revision rates with pre-revision and post-revision flow and PI values; one-year graft patency rates for the 1,710 (62.5 percent) grafts that underwent cardiac catheterization assessment and the sensitivity, specificity and positive and negative predictive values of using the transit-time flows to predict graft patency.

Single outlet grafts, sequential and T-grafts were excluded from the study. Intraoperative flow values of less than 20 mL/min in grafts were considered low flow grafts; more than 20 mL/min were considered normal graft flows. PI values of ≤3, 3-5, >5 were compared due to ambiguity in the literature regarding which PI threshold indicates a questionable graft. Graft patency was scored at one year by the FitzGibbon classification system. The decision of whether to revise a graft or not was left to the judgment of the attending surgeon.

The consortium of surgeons concluded that intraoperative transit-time flow data may be helpful in predicting long-term patency and also be useful for surgeons in deciding on whether to revise a questionable graft for patients undergoing CABG surgery.