Clinicians at the University of Calgary, Alberta, Canada sought to evaluate transit-time flow (TTF) as a tool to detect technical errors in arterial bypass grafts intraoperatively and predict outcomes. They measured flow in 336 consecutive patients who had an average of 3.02 grafts each. Ninety-nine percent of these bypass grafts were arterial. Three parameters: pulsatility index (PI), flow (cc/min) and diastolic filling (DF) were measured in 990 of the total 1,000 grafts.

If the measurements supported suspected graft malfunction, the grafts were revised. If no other signs/suspicion of graft malfunction existed and the PI was >5, grafts were not revised. Major adverse cardiac events (MACE) were correlated to the flow measurements.

They deemed 93% of the grafts were satisfactory and revised 14 conduits in 20 grafts that were suspected of being problematic. A high PI predicts technically inadequate arterial grafts during surgery, even if all other intraoperative assessments indicate good grafts; it also predicts outcomes, particularly mortality. Even though they concluded that flow and DF were not predictive of outcomes, they advise that intraoperative use of transit time flow measurements of arterial bypass grafts should become the standard of care.