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A Free-Access Online Interactive Simulator to Enhance Perioperative Transesophageal Echocardiography Training Using a High-Fidelity Human Heart 3D Model
Address correspondence to Susana Arango, MD, Division of Cardiothoracic Anesthesia, Department of Anesthesiology, The Visible Heart Laboratory, University of Minnesota, 2929 University Avenue SE Minneapolis, MN 55414.
University of Minnesota, Division of Cardiothoracic Anesthesia, Department of Anesthesiology, Minneapolis, MNThe Visible Heart Laboratories, Department of Surgery, Institute for Engineering in Medicine University of Minnesota, Minneapolis, MN
The clinical uses of perioperative transesophageal echocardiography have grown exponentially in recent years for both cardiac and noncardiac surgical patients. Yet, echocardiography is a complex skill that also requires an advanced understanding of human cardiac anatomy. Although simulation has changed the way echocardiography is taught, most available systems are still limited by investment costs, accessibility, and qualities of the input cardiac 3-dimensional models. In this report, the authors discuss the development of an online simulator using a high-resolution human heart scan that accurately represents real cardiac anatomies, and that should be accessible to a wide range of learners without space or time limitations.
TRANSESOPHAGEAL ECHOCARDIOGRAPHY (TEE) is a perioperative diagnostic tool whose application has grown significantly in recent years to include not only cardiac surgical patients but non-cardiac and intensive care patients as well.
Impact of critical care transesophageal echocardiography in medical-surgical ICU patients: Characteristics and results from 274 consecutive examinations.
Despite the American Society of Echocardiography (ASE) and the Society of Cardiovascular Anesthesiologists having recognized the potential for TEE to improve patient safety during general anesthesia in noncardiac surgical patients by offering “basic echocardiography” to anesthesiologists,
Council on Perioperative Echocardiography of the American Society of Echocardiography; Society of Cardiovascular Anesthesiologists. Basic perioperative transesophageal echocardiography examination: A consensus statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.
Guidelines for performing a comprehensive transesophageal echocardiographic examination: Recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.
In fact, the authors believe that one of the most significant barriers to rapid clinical adoption is the lack of accurate, detailed, and realistic training.
Prior to clinical experiences, knowledge acquisition relative to TEE comes in some combination of memorization and understanding. Although the intent of the basic and advanced ASE guidelines was to shorten the path to clinical application, learners are now more likely to memorize than to understand. This is evidenced by any number of available training tools, online or otherwise, whereby learners commit to memory the standard recommended echocardiographic views without necessarily understanding the relative cardiothoracic anatomies or potential nuances therein. The authors here contend, as do many, that to take echocardiography beyond mere vocation, experts must have an understanding of TEE that allows them to apply their understanding not idiosyncratically from one clinical scenario to the next, but rather to all clinical scenarios despite nuanced anatomy or extraneous interferences. To this end, the more familiar the learner is with 3-dimensional (3D) cardiac anatomy and the relationship of anatomic structures with the projections of the ultrasound beam of the TEE probe before applying this skill set in the perioperative setting, the more intentional the trainee will be when using the TEE probe to acquire, diagnose and communicate significant anatomic variations consistently and reliably.
In theory, simulation-based education tools should augment how echocardiography is taught and accelerate a learner's ability to successfully apply their understanding in the clinical setting.
To date, most hands-on simulators are expensive, difficult to store and transport, and do not lend themselves to self-guided learning. Although simulation-based TEE training is concentrated in large academic institutions, private practice colleagues—those who likely make up the majority of anesthesiologists and intensivists in the United States—have little recourse. Finally, almost all available simulators use hand-crafted, idealized heart models that often lack critical accuracy, detail, and anatomic variabilities.
Taken together, even simulation-based TEE training has been, for the most part, failing to adequately accelerate the rapid educational adoption necessary for all perioperative patients to benefit from the inherent values of echocardiography.
In hopes of bridging such deficiencies, the authors have developed means to further enhance echocardiography training, and have generated a novel, high-fidelity, low-cost online TEE simulator. This system uses high-resolution, three-dimensional human heart models that accurately represent cardiac anatomy in ways that can be standardized and made accessible to a wide range of learners. Herein, the authors describe the development of this novel educational tool.
Methods
This research conformed to the ethical guidelines of the 1975 Declaration of Helsinki and was reviewed and approved by [name deleted to maintain the integrity of the review process]. After consent, fresh human heart specimens unfit for orthotopic transplantation were procured in collaboration with LifeSource (Minneapolis, MN) and donated to the [name deleted to maintain the integrity of the review process]. Each specimen was cannulated through the great vessels and perfusion-fixed with 10% formalin for at least 24 hours to preserve an approximation of the end-diastolic state.
Next, a magnetic resonance imaging scan was performed (Siemens Healthineers, Erlangen, Germany) with a 0.7 × 0.8-pixel resolution. Anonymized datasets were imported into Mimics Innovation Suite (Materialise NV, Leuven, Belgium) software for segmentation and generation of the 3D cardiac model.
Extracardiac anatomy was derived from a contrast-enhanced computed tomography. The resulting models of such a heart (from magnetic resonance imaging) and surrounding organs (from computed tomography) were superimposed using anatomic landmarks and merged into a single image using Geomagic Design X (3D Systems, Rock Hill, SC) and Blender (Blender Foundation, Amsterdam, the Netherlands).
A model of the TEE probe also was generated in Blender using stock geometry. An online virtual TEE simulator was developed on Windows-10 64-bit (Microsoft, Inc, Redmond, WA) using Unity 3D (Unity Technologies, San Francisco, CA), a commercially available game engine.
Results
The authors successfully developed an interactive, online TEE simulator using a high-resolution 3D model of human hearts and surrounding organs—one such model presented of a patient with mild cardiac hypertrophy and a patent foramen ovale (Figs. 1 and 2). The authors believe this simulator bridges the gaps needed to facilitate the learner's understanding beyond rote memorization, and may prove to be an accessible, inexpensive, and immersive tool for accelerating the clinician's ability to apply their understanding in a meaningful way.
Fig 1A 3-dimensional model of the heart and the surrounding organs (esophagus, red arrow; stomach, yellow arrow).
The simulator has several features designed to enhance the learner's experiences and accelerate skill acquisition. First, the simulator has a central image on the learner's dashboard displaying a high-resolution 3D image of a human heart, the esophagus stomach, ribs, and the airway in the correct anatomic positions. A fully interactive echocardiography probe with an ultrasound plane fixed within the esophagus can be manipulated in real-time by the learner. The probe movements include withdrawal and advancement, turning right or left, omniplane angle rotation through 180°, anteflexion, and retroflexion. This is controlled using either a keyboard or a mouse. Second, there is a 2D representation of the ultrasound image that is being gained from the central 3D image that is displayed contiguously in the learner's dashboard. This is the image that a clinician would see on their ultrasound machine, the edges of which are demarcated by red and green lines that correspond to the left and right side of the central image, respectively. Probe depth and degrees of omniplane also are indicated in real-time on the learner's screen. (Fig 3 and Video 1). Third, if the learner wishes to review any number of ASE-recommended views automatically, they can do so by selecting that view from the available menu and view and a video player with the corresponding 2D echocardiographic view appears (Figs. 4, 5, and 6). From a programmed view, the learner can manipulate the probe to find adjacent echocardiographic planes or move on to the next ASE-recommended view. Fourth and final, to keep the learner engaged, as soon as the ultrasound plane has been manipulated to a view that has been recommended by the ASE, a video player with the corresponding 2D echocardiographic view appears as confirmation to the learner that they have attained the ’correct’ view.
Fig 3A midesophageal 4-chamber view of the heart as seen from the esophagus (left) and the corresponding echocardiographic image (right). The chest wall has been hidden.
Fig 4A midesophageal aortic valve short-axis view as seen from the esophagus (left) and the corresponding echocardiographic representation (bottom right), and a clip of an actual echocardiographic view (upper right).
Fig 5A transgastric midpapillary short-axis view as seen from the stomach (left) and the corresponding echocardiographic representation (bottom right), and a clip of an actual echocardiographic view (upper right).
Fig 6A midesophageal 5-chamber view as seen from the esophagus (left) and the corresponding echocardiographic representation (right). A menu with the predefined views to choose from can be seen on the top screen.
With these features, the authors believe a learner can perform a fully virtual examination on their own with immediate feedback on image quality and efficiency. As the learner moves from beginner to advanced skill levels, the central 3D model can be deactivated, leaving the learner with the 2D image as would be seen during an actual clinical care scenario. Importantly, the authors have made this online simulator accessible and free to users through their website (https://play.unity.com/mg/other/unitywebbuild).
Discussion
The authors describe herein the development of an intuitive simulation-based tool for acquiring, enhancing, and potentially accelerating all levels of learners’ TEE skills. This system is being made widely accessible and free to clinicians in training or those continuing their training. Although the authors have yet to quantitatively test the utility and usability, qualitatively, their own institution's trainees have found this tool to be useful for better preparing themselves during their cardiac anesthesia rotation, as well as their instructors consider it invaluable for teaching TEE in and around the operating rooms.
Simulation-based training is not novel, and a meta-analysis conducted by Jujo et al. reported on the value of simulators in acquiring competencies in TEE.
Yet, currently, such systems are quite expensive and, thus, largely restricted to academic simulation centers. In 2013, Vegas et al. developed an online TEE simulator, demonstrating improved acquisition of 20 standardized TEE views in a diverse group of learners.
The website on which this simulator can be accessed for free has become very popular among learners at all levels. Although this system is accurate, the 3D heart model employed lacks internal anatomic details, including atrioventricular valves, papillary muscles, ventricular trabeculae, and the nuances of the interatrial septum. Additionally, in their system, the TEE probe cannot be manipulated freely beyond what has been preprogrammed, leaving the learner blind to the relative anatomies lying 'between' standardized views.
In developing and making this freely available simulator online—one that is accurate, detailed, and realistic—the authors have bridged many deficiencies inherent to other currently available simulation-based training, many of which, because of the expense and components required, create barriers to wide-spread uses and implementations. The developed simulator-based training by the authors should accelerate the skill acquisitions needed to improve efficient and effective patient care by clinicians (ie, they will have an authentic understanding of cardiac anatomies, special orientations of the employed ultrasound beam directed toward the cardiac anatomy in question: applied echocardiography). Although the authors are confident in the tool they have developed and that it is ready for use, any such system has identified limitations on which the authors will focus their future work. In the first iteration the authors have made publicly available, they only have made 2 detailed human heart models available. To accurately represent variabilities in cardiac anatomy, including both adult and congenital patients, the authors have and continue to generate computational models of human hearts with a variety of clinical conditions (eg, with hypertrophic cardiomyopathy, septal defects, valve disease, and hearts in which valves have been replaced or repaired). Furthermore, they currently are working with developers to animate the myocardial wall and valve motion to provide learners with more physiologic detail. In the current system, the learners will not gain insights or experiences in the tensile forces needed to insert or manipulate the TEE probe within a patient, and, for such future iterations, will not have access to standardized ‘knobology’. Finally, to assess qualitative usability, the authors have trialed multiple iterations of this simulator with their cardiac-trained anesthesia staff, cardiothoracic anesthesia fellows, and residents. However, they have yet to quantitatively assess the value of this tool when compared with the currently available methods for teaching perioperative echocardiography.
Conclusions
The online simulator the authors have developed and presented here is a novel and powerful teaching tool. It aids in simplifying one's understanding of nuanced human cardiac anatomy and spatial 3D orientations as it relates to TEE. Furthermore, this simulator is currently offered as a free and interactive resource for academic programs involved in echocardiography education. The authors believe that this online simulator has the potential to change the landscape of global echocardiography training. Accordingly, additional educational research should be performed to confirm its value and expanded utilities.
Acknowledgments
The authors express their gratitude to the patients and families who have donated these human hearts for research and to LifeSource for their assistance in the recovery and transport of these organs.
Video 1. A user can move the plane along the designated track to obtain various echo views. As seen in the video, the plane is advanced down the “esophagus “and retroflexed to obtain a 4-chamber view and then advanced further to expose the coronary sinus. The 2-dimensional representation can be seen simultaneously on the left side of the screen with the omniplane degrees and the depth of the probe in the esophagus.
References
Arntfield R
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et al.
Impact of critical care transesophageal echocardiography in medical-surgical ICU patients: Characteristics and results from 274 consecutive examinations.
Council on Perioperative Echocardiography of the American Society of Echocardiography; Society of Cardiovascular Anesthesiologists. Basic perioperative transesophageal echocardiography examination: A consensus statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.
Guidelines for performing a comprehensive transesophageal echocardiographic examination: Recommendations from the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists.
ALTHOUGH THE use of transesophageal echocardiography (TEE) for the diagnosis and management of patients outside of the cardiac operating room has gained increased application and importance in recent years, there remains a significant barrier in accessing the training required to widely implement its use. 1 The American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists provide clear guidelines for obtaining a complete examination, with the National Board of Echocardiography producing the requisite standardized examination and defining the clinical experience necessary for certification in basic or advanced perioperative echocardiography.
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