Cut-off values for transit time flowmetry: are the revision criteria appropriate?

Area of Science:

• Cardiovascular Surgery
• Vascular Surgery
• Surgical Technology

Background:

• Previous studies, including the GRIIP trial, found no improvement in one-year graft patency after coronary artery bypass grafting (CABG) using intraoperative graft assessment with transit time flowmetry (TTF) and intraoperative fluorescent angiography.
• The utility of TTF in predicting saphenous vein graft (SVG) failure and clinical outcomes requires further investigation.

Purpose of the Study:

• To determine if specific TTF values are more predictive of SVG failure and/or major adverse cardiac events (MACE) at one year post-CABG.
• To re-evaluate the predictive value of TTF in the context of SVG patency and clinical outcomes.

Main Methods:

• Retrospective case-control study analyzing 65 SVGs from 44 patients previously enrolled in the GRIIP trial.
• Outcomes assessed included graft patency at 12 months and MACE (death, myocardial infarction, repeat revascularization).

Main Results:

• Mean TTF flow was a significant predictor of one-year SVG failure (AUC=0.698, p<0.01), with 31 mL/min identified as the optimal cutoff value.
• Grafts with mean flow <31 mL/min had a 50% occlusion rate versus 21.6% for grafts with mean flow ≥31 mL/min.
• Mean flow predicted early SVG failure (OR 0.95 [0.91-0.99] per mL/min, p=0.014), but TTF values did not predict MACE.

Conclusions:

• Intraoperative TTF can identify non-functional grafts during CABG.
• The value of TTF in improving one-year graft patency remains questionable, as specific thresholds did not consistently predict outcomes.