A comprehensive assessment of the mitral valve (MV) apparatus with 2-dimensional (2D) intraoperative transesophageal echocardiography (TEE) is necessary for successful surgical repair of a regurgitant MV.1–3 The demand for comprehensive imaging has further increased with advancements in MV repair4 and minimally invasive approaches.5 Recent studies have assessed MV prolapse (MVP) localization using real-time (RT) 3D transthoracic echocardiography relative to either 2D transthoracic echocardiography or 2D TEE.6–8 The transition from offline 3D reconstruction to intraoperative RT imaging has been facilitated by RT3DTEE, which allows for 3D imaging without interruption of the surgical procedure. Several pilot studies have explored the advantages of RT3DTEE for diagnosing MV pathology.9–13 Sugeng et al.14 used a considerable study population (47 patients) to explore new methods of prosthetic valve visualization using RT3DTEE, but 2D TEE was not used for comparison. Grewal et al.13 provided the first statistical comparison of MVP localization with RT3DTEE and 2D TEE in 42 individuals undergoing MV repair. They reported superiority of RT3DTEE over 2D TEE for several leaflet scallops and for the detection of chordal rupture.
Leaflet clefts are frequently encountered lesions in MV repair, although their detection by TEE has not been systematically investigated.15–17 Confident identification of leaflet clefts using 2D TEE has proven problematic and may adversely affect the outcome of MV repair.
This prospective observational trial was designed to test whether RT3DTEE is superior to 2D TEE in the detection and localization of MVP and ruptured chordae tendineae. In addition, although cleft assessment was not part of our standard 2D TEE routine, we hypothesized that RT3DTEE would be feasible and accurate for the assessment of MV leaflet clefts.
Sixty-two consecutive patients with mitral regurgitation (MR) who were scheduled for MV repair because of suspected MVP were enrolled in this study after permission from the Institutional Ethics Committee was obtained. The only exclusion criterion was contraindication to TEE. All studied patients provided informed written consent to participate in the investigation.
Two-dimensional and RT3DTEE were performed using an iE33 system equipped with an X7-2t matrix array transducer (Philips Medical Systems, Bothell, WA) after the induction of anesthesia. Five echocardiographers certified by the European Association of Echocardiography, with additional training in RT3DTEEa (TS, MH, CS, TM, and JM),b acquired the images. All operators performed TEE on a similar number of cases, and no priority was given to any specific operator.
The TEE examination was conducted following our standard clinical intraoperative TEE protocol (described below), which is based on the American Society of Echocardiography/Society of Cardiovascular Anesthesiologists guidelines1 and newer literature.18,19 A single echocardiographer acquired both 2D and RT3DTEE images during the same examination to minimize the potential effects of alteration in hemodynamic status and to minimize bias caused by variability among echocardiographers.
Image quality was graded as excellent, satisfactory, or poor by the interpreters depending on the display of the entire profile of the MV.
The 2D TEE Examination
The MV was examined in multiple cross-sectional views. They were optimized to display the entire MV taking care to optimize detail and image quality by adjusting the sector depth, width, lateral gain, and transducer frequency settings. The MV was imaged in the midesophageal (ME) 5-chamber views at 0°, which transected the anterior segments (A1/P1), followed by gradual advancement of the probe to acquire the ME 4-chamber view at 0°, in which the adjacent middle and caudal segments were visualized varying with patient anatomy and the probe position (A2/P1 or A2/P2, further caudal A3/P2 or A3/P3). Next, the 60° ME commissural view (with clockwise and counterclockwise rotation and withdrawal or advancement of the probe anterior [A1-A2-A3], middle [P1-A2-P3], and posterior [P1-P2-P3]), the 90° ME 2-chamber view (P3, free margin A3-A1), and an anterior, middle, and posterior section of the 120° to 150° ME long-axis view (A1-P1, A2-P2, A3-P3) were obtained. The 2D examination was supplemented by color Doppler recordings of the MV imaging planes and whenever feasible by a transgastric basal short-axis view.
The RT3DTEE Examination
Starting in the ME 4-chamber view, 2D images were optimized in the “x-plane” mode (featuring 2 orthogonal 2D sections) before RT3DTEE recordings were acquired in the 3D zoom mode. This mode displays a selectable pyramidal volume that can be focused to capture the MV with maximum resolution.
The 2D and RT3DTEE images were interpreted offline by 2 separate investigators certified by the European Association of Echocardiography and the German Association of Anesthesiology and Intensive Care with additional training in RT3DTEE (HR, CR), blinded to patient data, images of the other modality, preoperative diagnosis, and intraoperative findings. TEE data were stored on an external workstation with 2D and 3D files maintained in separate locations. Each interpreter examined the 2D and 3D recordings of 31 randomly selected patients in a randomized order.
MVP was defined as the displacement of leaflet tissue above the mitral annular plane into the left atrium by at least 2 mm during systole, considering the annular saddle shape.18
Three-dimensional interpretation was performed on 3D zoom recordings using Qlab 7.1 software (Philips Medical Systems). An initial en-face view of the left atrial perspective of the MV was used for the primary orientation and adjustment of gain and color schemes. The image was rotated to resemble the surgical orientation, with the aorta at 12 o’clock (Fig. 1a). The image was tilted to the left and right to compensate for the saddle shape of the MV19 and detect prolapsing scallops, chordal ruptures (systole), and leaflet clefts (early diastole). A more detailed inspection of the lesions was performed in the multiplanar reconstruction (MPR) mode of the same RT image, which features 3 cross-sectional views in any desired plane or angle (Fig. 2). The default settings of the MPR mode provide 2 orthogonal planes intersecting approximately the short and long axis of the MV annulus when recorded from an initial 2D ME 4-chamber view. Using the 3D image for orientation, these planes can be adjusted by the operator to intersect any leaflet or scallop. Additionally, the third, horizontal, plane can be adjusted to detect displacement inside the left atrium during systolic frames. Dragging the short-axis plane from one commissure to the other in a systolic frame (with adjustments to compensate for the curved commissural line) allows both MV leaflets to be inspected for the displacement of leaflet tissue into the left atrium past the mitral annular plane in systolic frames. Clefts through the anterior or posterior leaflet that lack connective tissue were assessed in frames before and after end systole and evaluated at different gain levels for consistency.
The MV was assessed from the opened left atrium during cardiopulmonary bypass (Fig. 1c). Six cardiac surgeons performed the operations in this study. The operating surgeon inspected the MV in the arrested heart for ruptured chordae and clefts that required surgical repair. The left ventricle was filled with saline to test for regurgitation and MVP, which was classified according to the Carpentier nomenclature.1
Variables assessed with both 2D and RT3DTEE were the absence or presence of MVP, the localization of the predominant prolapse, the localization of all prolapsing scallops of each patient, the scallop of origin of ruptured chordae tendineae, and the image quality of 2D and 3D images of each patient. Detection and localization of leaflet clefts were assessed with RT3DTEE, but not with 2D TEE.
The sensitivity and specificity were calculated for 2D and RT3DTEE for MVP presence, predominant scallop, prolapsing scallops, ruptured chordae tendineae (per scallop), and leaflet clefts. The accuracy for each scallop was determined as the sum of the true positive and true negative divided by the number of cases investigated. Differences in accuracy of 2D and RT3DTEE for the respective lesions of each scallop were assessed using 2-sided statistical testing and by the calculation of 2-sided 95% confidence intervals (CIs) for differences in paired-sample proportions according to methods described by Tango20 with the difference in proportions (delta statistic) = 0. Any P values <0.05 were considered significant findings. Image quality was analyzed with the Wilcoxon signed rank test. Agreement of RT3DTEE and 2D TEE images with surgical findings was assessed using Cohen kappa (κ) coefficient.21 κ [0.81–1.00] was considered “almost perfect,” κ [0.61–0.80] “substantial,” κ [0.41–0.60] “moderate,” κ [0.21–0.40] “fair,” and κ [0.0–0.20] “slight agreement.”21 The 95% CIs for κ bias-corrected and accelerated bootstrap intervals were determined; each interval was calculated from 1000 bootstrap samples. After 6 months, the studies of 20 patients were randomly selected, reviewed, and tested for inter- and intraobserver variability using the κ statistic. Statistical testing and the calculation of CIs were performed using the statistical software R 2.10.1 (Bell Laboratories, Murray Hill, NJ) and SPSS Statistics 19 (IBM, Armonk, NY). Bootstrapping was performed using the R package version 1.2-41.
As determined by the cardiac surgeon, the underlying cause of MR was myxomatous degeneration in 52 cases (21 with leaflet clefts), functional or ischemic in 9, and an isolated leaflet cleft in 1 case. The details of the surgical inspection are summarized in Table 1 and the findings for each of the 6 scallops are presented in Tables 2 and 3. The majority of lesions involved the posterior leaflet. Thirty-six patients were treated with minimally invasive surgery via lateral thoracotomy, and 17 patients received valvular replacement instead of repair. Thirty-five patients had concurrent surgery (tricuspid valve reconstruction, closure of persisting foramen ovale, myxoma, coronary artery bypass grafts, aortic valve replacement, grafting of the aorta, myocardial resection). Surgical MV procedures are listed in Table 4. There was a frequent incidence of complex MV disease (MVP involving >1 scallop [19 patients]). Figure 2 and online Figures 1 and 2 (see Supplemental Digital Content 1, http://links.lww.com/AA/A432, and 2, http://links.lww.com/AA/A433; see Appendix for online figure legends) show different cases of complex MV disease. Further patient characteristics are shown in Table 5. TEE acquisition did not prolong or interrupt surgical procedures and no patient was subsequently excluded from our study.
Mitral Valve Prolapse
The presence or absence of MVP was diagnosed correctly in all 62 cases (100%) using RT3DTEE and in 57 cases (91.9%) using 2D TEE (difference in proportions = 8.1%, CI [1.8%, 17.5%], P = 0.025). In the 52 patients with MVP, the predominant prolapse was correctly diagnosed with RT3DTEE in 51 cases (98.1%), and was misdiagnosed as occurring in A3 instead of P3 in 1 case. The predominant prolapse was accurately diagnosed in 46 cases (88.5%) with 2D TEE (difference in proportions = 9.6%, CI[ −0.5%, 21.5%], P = 0.059).
In evaluating the predominant prolapse as well as all prolapsing scallops, RT3DTEE was identical to the surgical inspection in 48 of the 62 study cases (77.4%) compared with 27 cases (43.5%) using 2D TEE (difference in proportions = 33.9%, CI [17.5%, 48.6%], P < 0.001). Agreement analysis with κ revealed substantial agreement of surgical findings and RT3DTEE (κ = 0.69, CI [0.54, 0.81]) compared with the fair agreement of surgical findings and 2D TEE (κ = 0.28, CI [0.17, 0.42]). When considering the potential impact of surgical approach (e.g., lateral thoracotomy versus sternotomy), agreement of both 2D and 3D TEE was lower in patients operated with the lateral thoracotomy approach. This decline affected both methods to the same extent. Accuracy was calculated separately for each of the 6 MV scallops for further differentiation (Table 6). RT3DTEE accuracy was significantly higher in scallops A2 (difference in proportions = 11.3%, CI [2.3%, 22.2%], P = 0.020), P1 (difference in proportions = 19.4%, CI [6.6%, 32.5%], P = 0.005), and P2 (difference in proportions = 16.2%, CI [9.0%, 27.2%], P = 0.002). The most frequent error in 2D TEE was differentiating P1 and P2 in posterior prolapse (10 cases), as shown in Figure 3.
Surgical inspection identified 37 and 25 patients with and without chordal rupture, respectively. RT3DTEE correctly diagnosed the presence or absence of chordal rupture in 59 of these patients (95.2%) as opposed to 43 patients (69.4%) using 2D TEE (difference in proportions = 25.8%, CI [16.6%, 37.9%], P < 0.001). Agreement of TEE and surgical reference regarding the scallops of origin of ruptured chordae was almost perfect using RT3DTEE (κ = 0.82, CI [0.68, 0.93]) and fair using 2D TEE (κ = 0.27, CI [0.14, 0.44]). Chordal rupture of the posterior leaflet is compared in Figures 3 and 4. Online Figure 2 (see Supplemental Digital Content 2, http://links.lww.com/AA/A433; see Appendix for online figure legends) shows chordal rupture of the anterior leaflet.
The analysis by scallop is listed in Table 6. The accuracy of RT3DTEE was significantly higher for the most frequent lesions, scallop P2 (difference in proportions = 24.2%, CI [13.1%, 36.7%], P < 0.001), and for A2 (difference in proportions = 6.5%, CI [0.2%, 15.4%], P = 0.046). There were 2 cases of papillary muscle rupture and both were correctly identified by either method.
The surgeon described 22 and 40 patients with and without leaflet clefts, respectively. RT3DTEE was feasible for the detection of surgically relevant MV leaflet clefts (Fig. 5) with a substantial agreement of RT3DTEE and intraoperative findings (κ = 0.65, CI [0.44, 0.81]). Five clefts reported by surgical inspection were not detected by RT3DTEE. Conversely, 7 clefts reported by RT3DTEE were not reported by surgical inspection (Table 6), which equals a false-positive rate of 17.5%. All true-positive clefts detected with RT3DTEE were localized accurately.
Three-dimensional zoom recordings had an average of 10.3 ± 2.1 frames per second compared with 42.8 ± 8.4 in 2D recordings. Image quality was rated excellent in 64.5%, satisfactory in 21.0%, and poor in 14.5% of the 3D examinations compared with 74.2% excellent, 24.2% satisfactory, and 1.2% poor in 2D. The mean image quality rating in 2D TEE was better than in RT3DTEE (P = 0.03). Poor 3D image quality was attributable to (a) an incomplete capture of the MV structures in a single 3D clip (n = 3), (b) interruption of acquisition by the surgical procedures (n = 2), and (c) poor echocardiographic signal quality (n = 4). None of these patients was excluded from the statistical evaluation.
Inter- and Intraobserver Agreement
Inter- and intraobserver agreement was substantial for both methods with a median κ value of 0.75 (range [0.35; 0.83]) and 0.80 (range [0.44; 0.89]) for inter- and intraobserver interpretations, respectively.
Mitral Valve Prolapse
RT3DTEE was more accurate than 2D TEE for the diagnosis of MVP in patients with MR. However, the predominant prolapse was correctly identified in the majority of cases using both RT3DTEE and 2D TEE. Although 2D TEE was reliable for the localization of a major prolapse of the MV, RT3DTEE was more accurate in detecting all prolapsing scallops in complex cases or excluding the involvement of adjacent scallops. The close visual resemblance of the 3D images to the surgical inspection is an advantage of RT3DTEE and was confirmed by the κ analysis, which illustrated a large difference of 2D versus 3D agreement with the surgeon when evaluating the entire valve for prolapsing scallops (difference in proportions = 33.9%) and for chordal ruptures (difference in proportions = 25.8%) (Figs. 3 and 4). However, superiority of RT3DTEE was not proven for all scallops. This effect is related to the small number of lesions in less frequently involved scallops (Table 6). Differences were significant in scallops P1 and P2, which accounted for two-thirds of all prolapsing scallops. Similar results were obtained for chordal rupture with significance for scallop P2 and a trend for P1. The frequent incidence of P2 lesions is consistent with the published literature22 and may reflect surgical patient selection.23,24
The differentiation of P1 versus P2 or a combined involvement is challenging in 2D TEE images (Figs. 3 and 4). Slight differences in patient anatomy or probe position may cause alterations in 2D sections, leading to intersection with the scallop that is adjacent to the expected one. The challenge increases when 2 scallops appear simultaneously in one 2D section (Fig. 3a). Diagnosis in these cases was better using RT3DTEE, in which the physiological interscallop indentations were observed in 3D en-face views, which facilitated the localization of MVP.
Three-dimensional images obviate these difficulties by including the entire information of the valve that is necessary for spatial orientation in 1 image (Fig. 2). MPR planes, which are very similar to 2D sections, can be obtained from the same heartbeat and can be arranged freely, to intersect the MV annulus anywhere.
Although 2D TEE can detect chordal ruptures sensitively,25 localization remains challenging (Fig. 3) (online Fig. 2, http://links.lww.com/AA/A433; see Appendix for online figure legends) because these fine structures only partially appear in the image, often without visualization of their leaflet insertion. Updating the results on RT3DTEE in previous studies,7,26 we found that the insertion at the leaflet of the majority of ruptured chordae can be detected accurately (Fig. 4) (online Fig. 2, http://links.lww.com/AA/A433). The visualization of multiple ruptured chordae in one “bird’s eye view” provides an advantage for the precise description of complex MV pathology.
Even though 22 patients in our study were reported to have MV leaflet clefts, the anatomical definition of leaflet clefts is not well defined and their clinical significance is uncertain. In addition to visualization, it is challenging to distinguish physiological interscallop indentations27 from clefts in the mitral leaflets that cause regurgitation and require surgical intervention. These clefts can arise from interscallop indentations that exceed what Victor and Nayak27 refer to as anatomically regular “slits” (online Fig. 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A432; see Appendix for online figure legends), and intrascallop clefts in abnormal places20 (Fig. 5). We found substantial agreement of RT3DTEE with the surgical inspection. Seventeen clefts were correctly visualized using RT3DTEE, providing new information that may be used for surgical planning. Two reasons likely account for the number of false-positive clefts in RT3DTEE: the overestimation of interscallop indentations at low gain settings, and the exceptionally frail leaflet tissue that sometimes presents as a tissue defect in RT3DTEE (Fig. 6) and leads to a false-positive diagnosis. When imaging with a low number of frames per second, a cleft may be visible in one single frame only, making it difficult to determine true anatomical clefts from imaging artifacts.
Limitations of 2D TEE
Intraoperative 2D TEE is the standard method for the evaluation of MV pathology and provides accurate data with proven feasibility in the operating room.2,25,28 However, spatial orientation is often difficult with 2D TEE, and interpretation of 2D images remains challenging and requires a high level of expertise. Clinicians limited to 2D imaging are often confronted with ambiguous 2D recordings, in which the affection of adjacent scallops cannot be distinguished with certainty. Information regarding the position of the probe at the moment of acquisition and the impact of manual adjustments on images is essential for correct interpretation, thus making it highly operator-dependent. Ahmed et al. suggested that the limitations of conventional 2D TEE lie in its inability to display the entire surface of the mitral leaflets in the short axis, and true localizations may differ from the established standard 2D sections.29,30 Further factors leading to these aberrations are anatomical differences of patients, the left lateral positioning in minimally invasive surgery, and cases with complex MV disease.6 Sensitivity has been reported between 50% and 96% for the diagnosis of MVP with 2D TEE.2,6,9,28 The accuracy of 2D TEE in our study is consistent with these numbers and reflects the aforementioned challenges. Color Doppler helps with orientation in addition to 2D imaging of the MV apparatus.
Limitations of RT3DTEE
Although the spatial resolution of RT3DTEE technology has advanced notably, temporal resolution remains limited. Three-dimensional zoom recordings offer approximately 25% of the frame rate of 2D imaging, which may lead to an inability to diagnose scallop pathologies associated with motion, such as ruptured chordae and leaflet clefts. RT3DTEE also has a greater tendency to misidentify normal structures as pathology (Fig. 6), especially when the image gain is reduced to suppress image noise.27,29 In our study, this led to a false-positive rate of 17.5% for leaflet clefts with respect to the surgical findings.
RT3DTEE acquisition of one 3D zoom-mode recording takes approximately 1 to 2 minutes. Considering that one recording has to be made compared with a full set of 2D recordings, acquisition of RT3DTEE is considerably faster. However, thorough interpretation of a 3D zoom-mode recording requires gain changes, rotation, and MPR analysis after acquisition, which is not necessary with 2D TEE interpretation.
In this study, the average image quality was rated higher with 2D TEE than RT3DTEE. This difference may have been attributable to a longer experience with 2D acquisition. RT modes such as the 3D zoom mode can obviate the problem of artifacts caused by the stitching of subvolumes with faulty alignment caused by arrhythmia or movements.31 Unfortunately, it is restricted by its maximum image window width, and anatomically significant structures may be cut off in large valves.
At present, there is only one vendor who offers RT3DTEE for intraoperative use, and the analysis of RT3DTEE data requires specific software, which limits widespread clinical availability.
Limitations of This Study
The comparison of 2D versus RT3DTEE was performed after surgery to ensure proper blinding of the interpreters. The relative diagnostic inferiority of 2D TEE, as shown in our study, might have been influenced by the offline analysis of 2D images. In everyday clinical practice, the intraoperative physician is using color flow Doppler along with 2D imaging. Two-dimensional interpretation also depends on the experience of the echocardiographers and the knowledge of the probe depth or right-left turn. This information was not recorded and could have impaired 2D interpretations, whereas it is not necessary for RT3DTEE interpretation because the images contain all of the information.
In several cases, more leaflets were reported as prolapsing in RT3DTEE images than during surgical inspection. Using TEE before institution of cardiopulmonary bypass, MV function can be evaluated in a relatively physiological state (assuming normal ventricular loading conditions). However, the surgeon is evaluating the anatomical features in a resting heart devoid of blood during the surgical inspection period. Consequently, smaller lesions may be missed by the surgeon despite a correct diagnosis with TEE.
In this prospective study of intraoperatively acquired TEE imaging, RT3DTEE proved feasible and more accurate than 2D for the detection, localization, and description of MVP and ruptured chordae tendineae. The new generation of RT3DTEE imaging facilitates the detection of leaflet clefts. RT3DTEE provides a full view of the MV annulus, which can be further “dissected” offline so that any component can be interrogated. Two-dimensional TEE is an indispensable tool in MV surgery, but RT3DTEE offers distinct improvements in spatial orientation and visualization of valvular pathology. The increasing sophistication of MV surgery requires that the surgeon be supplied with the best available imagery. We recommend RT3DTEE as a routine supplement to intraoperative MV imaging.
Appendix: Online Figure Legends
Online Figure 1: Complex mitral valve prolapse (MVP) involving all scallops. Severe mitral valve (MV) bi-leaflet prolapse disease that involved all scallops. All images are from the same patient. Red lines mark the annular level in both 2-dimensional (D) and real-time 3-dimensional transesophageal echocardiography (RT3DTEE) images. (a-d) Standard 2D ME sections. It seems as if there is no A1 prolapse in (a) and no A2 prolapse in (d). In (b), A2 prolapse is visible, in (c), A1 and A2 prolapse is visible, which would contradict (a) and (d). (c): in this complex case involving bi-leaflet prolapse of different extents, it is difficult to specify which scallops are intersected. An MPR would be helpful. (e-f): RT3DTEE images. (e) The annular level and the commissural line are marked in white. (*) marks PL interscallop indentations. In (e), all scallops, with the exception of A2, are clearly prolapsing. (f) The same image turned clockwise and cropped from the PMC shows that A3 and A2 are also prolapsing above the annular level (red line). [AL: anterior leaflet; ALC: anterolateral commissure; Ao: aortic valve; LV: left ventricle; ME: midesophageal; MPR: multiplanar reconstruction; PL: posterior leaflet; PMC: posteromedial commissure]
Online Figure 2: Anterior prolapse with chordal ruptures. (a-d) Four standard midesophageal (ME) views of the mitral valve (MV) in 2-dimensional (D) transesophageal echocardiography (TEE) reveal prolapse and chordal rupture of the anterior leaflet. (e) Four Chordae (black arrows) can be distinguished in the real-time (RT) 3D en-face view at end systole, including their exact origin, corresponding to the surgeon’s view. (f) Surgeon’s view (minimally invasive access) with prolapse and broad tear-off of chordae in A2 (black arrows).
Name: Maximilian Dominik Hien, MD.
Contribution: This author assisted in the study design, conducted the study, analyzed the data, and wrote the manuscript.
Attestation: Maximilian Dominik Hien has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is responsible for archiving the study files.
Name: Helmut Rauch, MD.
Contribution: This author assisted in the study design, conducted the study, and supervised the performance of the study.
Attestation: Helmut Rauch has seen the original study data, reviewed the analysis of the data, and has approved the final manuscript.
Name: Artur Lichtenberg, MD.
Contribution: This author assisted in the conduct of the study and the revision of the manuscript.
Attestation: Artur Lichtenberg has seen the original study data, reviewed the analysis of the data, and has approved the final manuscript.
Name: Raffaele De Simone, MD.
Contribution: This author conducted the study, assisted in the writing and revising of the manuscript, and provided valuable advice.
Attestation: Raffaele De Simone has seen the original study data, reviewed the analysis of the data, and has approved the final manuscript.
Name: Marc Weimer, DSc.
Contribution: This author assisted in data analysis, calculated the statistics, and acted as a consultant.
Attestation: Marc Weimer has seen the original study data, reviewed the analysis of the data, and has approved the final manuscript.
Name: Oriana Amanda Ponta, MSc.
Contribution: This author assisted in data analysis, calculated the statistics, and acted as a consultant.
Attestation: Oriana Amanda Ponta has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is responsible for archiving the study files.
Name: Christian Rosendal, MD, DESA.
Contribution: This author assisted in the study design, conducted the study, analyzed the data, and wrote the manuscript.
Attestation: Christian Rosendal has seen the original study data, reviewed the analysis of the data, and has approved the final manuscript.
This manuscript was handled by: Martin J. London, MD.
The authors thank Thomas Müller, Tanja Sacconi, Christoph Schramm, and Johann Motsch for their assistance in data acquisition. They also thank the Research Training Group 1126 and the German Research Foundation (DFG) for supporting the research project.
a Two-day intensive training course on 3D TEE and clinical practice.
b Tanja Sacconi, Maximilian Hien, Christoph Schramm, Thomas Müller, and Johann Motsch.
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