Prediction of graft patency during the year following coronary artery bypass grafting: Preoperative computed tomography-derived fractional flow reserve versus intraoperative transit-time flow measurement.

Abstract

Preoperative cardiac computed tomography-derived fractional flow reserve (CT-FFR) and intraoperative transit-time flow measurement (TTFM) values were compared with graft patency after coronary artery bypass grafting (CABG). One hundred and eight patients who underwent isolated CABG using an in situ internal thoracic artery (ITA)-based composite graft and whose CT-FFR values were obtained were included. TTFM values (mean graft flow [MGF; mL/min], pulsatility index [PI], and diastolic filling percentage [DF%]) were obtained for each anastomosis in all study patients. Early angiographies examined 342 anatomoses performed in all 108 patients, and 1-year angiographies examined 310 anastomoses performed in 97 patients (89.8%). Angiographic findings of graft flow were categorized as perfectly patent, bidirectionally competitive, unidirectionally competitive, and occluded. Receiver operating characteristic (ROC) curve analysis of CT-FFR and TTFM values for predicting angiographic findings was performed, and cutoff values and area under the ROC curve of CT-FFR and TTFM values were identified. The early angiograms identified 281 (82.2%) perfectly patent grafts, 33 (9.6%) bidirectionally competitive grafts, 27 (7.9%) unidirectionally competitive grafts, and 1 (0.3%) occluded graft. These numbers were 278 (89.7%), 13 (4.2%), 8 (2.6%), and 11 (3.5%), respectively, on the 1-year angiograms. CT-FFR values in coronary arteries with perfectly patent, bidirectionally competitive, and unidirectionally competitive grafts were significantly different during the year (0.640, 0.807, and 0.816, respectively, in early angiograms [P < .001] vs 0.658, 0.841, and 0.857, respectively, in 1-year angiograms [P < .001]). Cutoff values of CT-FFR, MGF, PI, and DF% predicting competitive graft flow were 0.774, 11 mL/minute, 2.8, and 72%, respectively, in early angiograms and 0.767, 12 mL/minute, 2.8, and 58.0%, respectively, in 1-year angiograms. CT-FFR values better predicted the early and 1-year competitive graft flow compared to TTFM values (MGF, P < .001; PI, P < .001; DF%, P < .001). The diagnostic accuracy of CT-FFR values for predicting competitive graft flow during the year following CABG using an in situ ITA-based composite graft was high and superior to TTFM values.