Transthoracic echocardiography (TTE) is a valuable tool for echocardiographic evaluation of the pulmonic valve (PV); however, poor acoustic windows, body habitus, and the thin leaflets of the PV limit its use.1 Typically, in a conventional parasternal window, only 2 leaflets are seen in its long axis, and there are no dedicated views to visualize all 3 leaflets except in rare cases when the valve is displaced anteriorly.2 Visualization of the PV by transesophageal echocardiography (TEE) also has its limitations. The anterior location and thin leaflets of the PV make TEE evaluation challenging. Nevertheless, TEE evaluation in the intraoperative setting is useful in identifying infectious lesions of the PV, congenital malformations, or the presence of pulmonary stenosis or regurgitation. TEE also is useful for immediate intraoperative assessment after PV interventions. The conventional TEE views—the midesophageal (ME) short-axis view of the aortic valve, the ME right ventricular (RV) inflow-outflow view, ME ascending aortic short-axis view, upper esophageal aortic arch short-axis views, transgastric (TG) RV basal view, and TG RV inflow-outflow view3—allow for PV visualization only in long axis. None of these views allows visualization of the PV in short-axis. Simultaneous orthogonal plane imaging coupled with matrix array probes that allow 2D and 3D imaging allow for a second adjustable orthogonal imaging plane. This secondary plane can be tilted using the trackball. We describe the use of simultaneous orthogonal plane imaging with tilt to enable simultaneous evaluation of the PV in both short- and long-axis views and present our observational analysis of its feasibility in 100 consecutive patients undergoing intraoperative TEE.
The objective of this study was to evaluate the feasibility of using simultaneous orthogonal plane TEE imaging with tilt to visualize and evaluate PV in its short axis.
With IRB approval that waived the requirement for written patient consent, 100 consecutive adult patients undergoing intraoperative TEE for cardiac or noncardiac surgery were enrolled in the study. Study images were acquired by 3 physician anesthesiologists who are certified by the National Board of Echocardiography for Advanced Perioperative Transesophageal Echocardiography. Imaging and assessment of the PV, as well as data collection, were performed in real time in the operating room.
Following standard surgical protocol, a 3D matrix array TEE probe (iE33; X7-2t; Philips Healthcare Inc., Andover, MA) was inserted into the esophagus after induction of anesthesia and a comprehensive TEE examination was performed using American Society of Echocardiography and Society of Cardiovascular Anesthesiologists (ASE/SCA) guidelines.3
After optimizing the view of the PV in the ME RV inflow-outflow view, PV leaflets were imaged in its long axis (Table 1, Figs. 1 and 2). Simultaneous orthogonal plane imaging was then activated, enabling visualization of the original image on the left side of the screen (primary plane) and the secondary image (90° omni plane from the original) on the right side of the screen (Fig. 3). However, the plane of the PV is superior and oblique to the plane of the aortic valve with a tilt to the left. Adding a tilt (−30 to +30) using the trackball for the cursor will account for this and further optimize the secondary image to provide an optimal 2D image of PV in short-axis view (Video 1, Supplemental Digital Content 1, http://links.lww.com/AA/B152; Figs. 1 and 4). Flow assessment across the PV using color Doppler was performed in all cases using Nyquist limits of 50 to 60 cm/s (Video 2, Supplemental Digital Content 2, http://links.lww.com/AA/B153; Fig. 5). Planimetry was performed when feasible.
One hundred patients were enrolled consecutively over a 6-month period. Most subjects (76%) presented for coronary artery bypass graft (CABG) surgery, 7% for valve surgery (aortic and mitral), 7% for CABG plus valve surgery, and 10% for other noncardiac procedures. Using the short-axis view, the PV was successfully visualized with all 3 leaflets in 65% (65/100) of cases and 2 leaflets in 32% of the cases. In 3% of cases, the imaging was poor and we could barely visualize one leaflet. Although, incidentally, more males were enrolled in the study, the ability to visualize leaflets did not differ by gender. We were able to evaluate the flow across the valve in short axis and long axis during simultaneous orthogonal plane imaging using color Doppler in all cases (Fig. 5). No pathologies were identified in our study group. Planimetry for valve area was possible when all 3 leaflets were visualized (Fig. 6). The age, height, weight, or body surface areas did not appear to influence the imaging success rate.
The newer generation matrix array probes that enable acquisition of 3D images also allow for real-time, simultaneous orthogonal plane imaging. Two 2D images are displayed, allowing the appreciation of additional clinical information without postprocessing. In addition, the use of vertical or lateral tilt of the secondary plane makes it possible to obtain additional views that may not otherwise be possible with the rotation of the multiplane angle to an extra 90°. It is important to inspect the PV during routine examinations. Being able to see the PV in both long and short axis can be valuable, especially with pathology involving structures of the right side of the heart. To the best of our knowledge, this is the first study reporting the use of simultaneous orthogonal plane imaging technology to evaluate the PV in its short axis during a TEE examination.
ASE/SCA guidelines recommend specific cross-sectional views in a comprehensive multiplane TEE examination.3 However, there is a distinct lack of nomenclature dedicated to PV as the main structure of interest in the standard views. An understanding of the PV anatomy is often dependent on the preoperative TTE assessment. PV is rarely visualized in short axis with conventional 2D TTE, although it may be feasible using 3D TTE imaging.4 Recognizing the limitation of echocardiography in short-axis imaging of the PV, Kivelitz et al.5 described the use of cine magnetic resonance imaging for in-plane visualization of the PV. In a prospective study, Kasper et al.6 demonstrated the usefulness of additional TG TEE views that improved visualization of the PV compared with standard views. However, the ability to see all 3 leaflets in a short-axis view was not described. Another useful long-axis view of the PV that allows spectral Doppler evaluation has been described in the upper esophageal aortic arch short-axis view.7 When establishing the guidelines and standards for 3D imaging, Lang et al.8 noted that only 2 leaflets of the PV can usually be simultaneously visualized by 2D echocardiography and that valve leaflets are difficult to visualize on the short-axis view. They described a useful 3D en face view of the PV using real-time or full volume 3D imaging, which allows the evaluation of all 3 leaflets concurrently in its short-axis. However, acquisition and optimization of the 3D images can be time-consuming and may need postprocessing. This alternative technique can complement ours, although its use is open for validation.
Several applications of simultaneous orthogonal plane echocardiographic imaging have been described, including its use in fetal imaging with transthoracic probes.9–11 This modality permits the display of a simultaneously adjustable biplane 2D image in real-time. From the primary image, a secondary image can be visualized at an orthogonal plane. The secondary image will be at the same depth as the primary imaging plane. The leaflets of the PV are defined by their relationship to the aortic valve (i.e., anterior, right, and left). In the primary image, the leaflet farthest from the probe is the anterior leaflet and proximal leaflet is usually the left or right. In the secondary image with tilt, the leaflet farthest from the probe is the anterior leaflet, the leaflet on right of the screen (distal to ascending aorta) is the left leaflet, and the leaflet on left of the screen is the right leaflet (Figs. 2 and 4). The use of color Doppler while visualizing the valve in long and short axis can further provide valuable information regarding flow characteristics, such as the presence of regurgitant jet and its spatial orientation to the leaflets or presence of turbulent flow (Fig. 5). Trace pulmonary regurgitation is a common finding in normal subjects. The presence of a pulmonary artery catheter may have minimal to no effect on the regurgitation.12 Pulmonary regurgitation can be seen because of annular dilation from pulmonary hypertension or connective tissue disorders. Additional etiologies include restricted leaflet mobility from carcinoid or rheumatic disease, congenital malformations, and previous surgeries. Pulmonary stenosis in disease states, such as congenital lesions involving the PV, carcinoid syndrome, or rheumatic heart disease, can result in turbulent flow. The ability to view PV in the short-axis view allows the use of planimetry to measure the valve area when all 3 leaflets are visualized, although the technique needs validation (Fig. 6).
The frame rate with simultaneous orthogonal plane imaging is reduced compared with traditional single-plane imaging, thus decreasing temporal resolution. Adding color Doppler will further reduce the frame rate. In 35% of our sample group, we were unable to visualize all 3 leaflets. In addition to sampling bias and subjective error, possible factors may be the oblique plane of PV, resulting in an inability to position the ultrasound beam across the PV, dropout because of the anterior location of the PV, presence of pulmonary artery catheter, thin leaflets, and calcified aortic valve resulting in shadowing. The presence of bicuspid PV may be another factor, but it is rare, and its true incidence is poorly studied because of difficulty in imaging the PV.13 In the 3 patients in whom we visualized only 1 leaflet, the imaging quality of the entire heart was poor. Most of our sample group underwent isolated CABG procedures. The presence or absence of aortic valve disease was not recorded, and hence, its influence on the success rate of visualization not evaluated. As with a short-axis evaluation of any other structure, spectral Doppler velocities are not possible with this technique because of the perpendicular orientation of the Doppler beam and blood flow. We did not assess intra- and interobserver variability or the influence of the pulmonary artery catheter on imaging quality, both of which could limit the validity of the presented data. Finally, none of the patients in our study underwent interventions involving the PV.
This relatively simple and feasible method provides additional information while evaluating the PV during TEE. Short-axis visualization may be beneficial when assessing spatial orientation of the existing pathology to the leaflets. It may facilitate better evaluation of prosthetic valves using color Doppler imaging. This technique is based on real-time imaging, as opposed to 3D imaging, which may require postprocessing and hence reduce the time required to evaluate the short axis view of the PV. Incorporating additional TEE views to the standard views can potentially improve comprehensive assessment of the PV.
In this study, we demonstrate the simplicity and feasibility of using a simultaneous orthogonal plane imaging technique. Routine incorporation of this view in a comprehensive intraoperative TEE examination will enable better evaluation of the PV. Further validation of this imaging technique is needed.
Name: Sanjay Dwarakanath, MB BS.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Sanjay Dwarakanath has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.
Name: Manuel R. Castresana, MD.
Contribution: This author helped conduct the study and write the manuscript.
Attestation: Manuel R. Castresana has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
Name: Amanda Y. Behr, MA.
Contribution: This author helped develop the medical illustrations in Figure 1.
Attestation: Amanda Y. Behr approved the final manuscript.
Name: Mary E. Arthur, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Attestation: Mary E. Arthur has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
The authors thank Nadine Odo, Georgia Regents University, for help in editing this manuscript and Carter Galbraith for editing the videos.
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