Computed tomography–derived fractional flow reserve versus transit-time flow measurement for predicting early competitive graft flow after coronary artery bypass grafting

OBJECTIVES: Competitive graft flow caused by functionally non-significant coronary stenosis may compromise graft performance after coronary artery bypass grafting (CABG). We compared the ability of preoperative computed tomography-derived fractional flow reserve (CT-FFR) and intraoperative transit-time flow measurement (TTFM) to predict competitive graft flow on early postoperative angiography. METHODS: This retrospective study included 235 patients who underwent isolated CABG using an in-situ internal thoracic artery-based composite graft and had preoperative CT-FFR values available. Intraoperative TTFM parameters, including mean graft flow (MGF), pulsatility index (PI), diastolic filling percentage (DF%), and percentage of backward flow (%BF), were recorded for each anastomosis. Early postoperative angiography was performed in all patients, and graft flow was classified as perfectly patent, bidirectionally competitive, unidirectionally competitive, or occluded. Receiver operating characteristic analyses were performed to compare the predictive performance of CT-FFR and TTFM parameters. RESULTS: Among 744 anastomoses (median, 3[3.0, 4.0] per patient), 602(80.9%) were perfectly patent, 69(9.3%) were bidirectionally competitive, 70(9.4%) were unidirectionally competitive, and 3(0.4%) were occluded. CT-FFR values increased according to the degree of competitive graft flow and demonstrated the highest predictive accuracy for competitive flow (cutoff 0.764; area under the curve[AUC], 0.845; P < 0.001). The predictive performance of CT-FFR was superior to that of all TTFM parameters, including MGF(AUC, 0.730), PI(AUC, 0.701), DF%(AUC, 0.625), and %BF(AUC, 0.707)(all P < 0.001). CONCLUSIONS: In patients undergoing composite CABG, preoperative CT-FFR demonstrated superior predictive performance compared with intraoperative TTFM parameters for early competitive graft flow. These findings support the integration of physiologic lesion assessment into surgical planning to optimize revascularization strategy.