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 network of 2 to 3 cm comprising multiple turbulent color flows arose from the proximal LAD and drained into the posterior aspect of the MPA.
The LAD fistula to the MPA was ligated after constructing the left internal mammary artery to the LAD graft. However, the RCA fistula was left alone due to its unfavorable location for exposure or ligation, and postoperative transcatheter embolization was planned.
Although various imaging modalities have been used, intraoperative 2D TEE has been used for diagnosis and evaluation of coronary artery fistulae.1–3 However, the limitations of 2D TEE make angiography the preferred method of visualizing this pathology.4 Manipulating the TEE probe to acquire appropriate 2D images and interpreting the images accurately are challenging in complex fistula pathology. Even under favorable conditions, greater effort may be required to obtain and combine multiple 2D images. The X-plane mode may partly overcome the limitation of 2D TEE imaging; it instantaneously produces an additional 2D image and multiplane angle, and angulation of the additional image to the original can be changed by adjusting knob and cursor line in the display without physically tilting the TEE probe. However, it also requires considerable effort to localize and intersect the targeted vascular flows in its 2D tomographic image planes and sometimes cannot visualize tortuous or nonparallel flows, as in the RCA of the present case.
By contrast, 3D full-volume CFD image could provide not only various intuitive cardiac images from any perspective (3D echocardiographic datasets) but also comprehensive delineation of the flows (3D CFD datasets) with less sophisticated localization of its ROI. The selective removal of 3D echocardiographic datasets by suppressing B/W is a key to visualize targeted flows and their distributions in the ROI.
A single clip of a 3D full volume with CFD image may be superior to angiography, which is more invasive and usually lacks spatial information. Furthermore, its applicability to the intraoperative setting is clinically important because intraoperative imaging modalities to evaluate coronary fistulae are limited. However, 3D CFD imaging requires a regular cardiac rhythm and brief cessation of ventilation for several seconds to avoid stitch artifacts. It requires fine adjustment in color-Doppler gain, scale, and filtering; exaggerated CFD signals increase the noise and complexity of flow, while heavily attenuated signals result in intermittent interruption of small or slower flows. It also depends on the axes of the Doppler signals and flows, although a turbulent fistula running perpendicular was well visualized. Its small-volume coverage (60° width and thickness) and poor temporal resolution (frame rate, < 10 Hz) may impede its analysis of wide and dynamic flows. In conclusion, intraoperative 3D full volume with CFD imaging is useful in evaluating coronary artery fistulae and their relationship to adjacent cardiac structures.
Clinicians Key Teaching Points
By Kent H. Rehfeldt MD, Nikolaos J. Skubas MD, FASE, and Martin J. London MD
* Visualization of coronary fistulae with 2-dimensional (2D) transesophageal echocardiography (TEE) necessitates multiple fine adjustments of nonstandard imaging planes. It is often difficult to accurately delineate the course of the complex, 3D communications.
* Simultaneous display of 2 orthogonal imaging planes is now possible with all currently marketed 3D TEE probes and may improve visualization of the tortuous course of coronary fistulae. However, even this mode may not provide adequate visualization.
* In this case of a patient undergoing off-pump coronary artery bypass surgery, 3D full-volume datasets with color-flow Doppler were obtained by using multibeat acquisition. Adjusting gain and compression and selectively suppressing the black-and-white component of the image enabled the imaging of the fistula tracks.
* Three-dimensional TEE imaging of coronary fistulae in the intraoperative setting allows recognition of these vascular abnormalities, delineation of their course, and may help confirm successful ligation. However, a relatively low frame rate, reliance on a regular heart rhythm, and a limited color Doppler imaging sector limit its utility.
Name: Joungmin Kim, MD.
Contribution: This author helped design and conduct the study, analyzed the data, and wrote the manuscript.
Attestation: Jungmin Kim approved the final manuscript.
Name: Ga-Yon Yu, MD.
Contribution: This author helped conduct the study and contributed for writing the manuscript.
Attestation: Ga-YonYu approved the final manuscript.
Name: Jungho Seok, MD.
Contribution: This author helped conduct the study.
Attestation: Jungho Seok approved the final manuscript.
Name: Chung-Sik Oh, MD.
Contribution: This author helped data analysis.
Attestation: Chung-Sik Oh approved the final manuscript.
Name: Seong-Hyop Kim, MD, PhD.
Contribution: This author helped data analysis.
Attestation: Seong-Hyop Kim approved the final manuscript.
Name: Tae-Yop Kim, MD, PhD.
Contribution: This author helped data analysis and design and conduct study.
Attestation: Tae-Yop Kim approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.