A 51-year-old woman underwent off-pump coronary artery bypass surgery. Preoperative coronary angiography showed 70% segmental stenosis in the midpart of the left anterior descending coronary artery (LAD) and multiple fistula tracks from the proximal LAD and the proximal right coronary artery (RCA) to main pulmonary artery (MPA) (Fig. 1).Pairs of orthogonal 2-dimensional (2D) midesophageal aortic valve images with color-flow Doppler (CFD) in "X-plane mode" that focused on the proximal RCA and LAD were taken by using intraoperative transesophageal echocardiography (TEE) (iE33™ and X7-2t™; Philips Healthcare, Bothell, WA) (Fig. 2, A and B; see Video 1, Supplemental Digital Content 1, http://links.lww.com/ AA/A713): the proximal LAD flow and multidirectional turbulent color jet branches suggesting known LAD fistulae flows were partly delineated, but the RCA flow and its fistula flow were not visualized. Spectral velocity tracing of pulsed-wave Doppler by placing the sample volume at the proximal LAD showed abnormal flow patterns comprising notched systolic antegrade flow and diastolic reversal flow, which presumably indicates the complexity of the flow pattern (Fig. 2C). However, sample volume might indicate mixing of the LAD and adjacent fistula flows, since the fixed sampling site could not consistently trace the LAD flow during the entire cardiac cycle.Electrocardiographically gated acquisition of 3D full-volume images with CFD was performed with brief cessation of mechanical ventilation. The regions of interest (ROI) of the echocardiographic image and color-Doppler box were placed on the assumed proximal LAD and RCA in 2D midesophageal aortic valve X-plane images. Seven narrow-volume datasets were rendered over 7 consecutive heartbeats and automatically integrated to produce a single 3D full-volume image with CFD data ( Fig. 3; see Video 2, Supplemental Digital Content 2, http://links.lww.com/ AA/A714 and see Video 3, Supplemental Digital Content 3, http://links.lww.com/AA/A715): echocardiographic gain, compression, and smoothing were adjusted to 15%, 25% to 35%, and 5/9, respectively. Next, 3D echo bright (black/ white, B/W) anatomic datasets were selectively removed by activating B/W suppression in on-cart after processing. Finally, only 3D CFD datasets remained in the display with the scale of 112.4 cm/s and depicted a multidirectional flow pattern (Fig. 3). For better delineation of the fistulae flows and their differentiation from coronary arterial flows, CFD gain, smoothing, and filter were adjusted to 40 to 50/100, 5/9, and 4 to 5/9, respectively. Back-and-forth toggling "B/W suppression" of the 3D CFD images with further fine rotation facilitated a more detailed understanding of their spatial relationships between the fistulae and adjacent cardiac structures. The overall extent and shape of the fistulae delineated in these 3D images corresponded well to the preoperative angiographic findings: a single fistula arose from the proximal RCA and drained into the anterior aspect of the MPA, and a fistula networ...