Virtual Dissection: Emerging as the Gold Standard of Analyzing Living Heart Anatomy

Virtual Reality Computed Tomography Evaluation - Anatomy and Clinical Implications for Valve-Sparing Aortic Root Replacement

BACKGROUND

Three-dimensional aortic root evaluation using virtual reality (VR) techniques for valve-sparing aortic root replacement (VSARR) preparation has not yet been implemented, so we demonstrated VR computed tomography (VR-CT) and assessed its utility for VSARR.Methods and Results: We enrolled 72 patients who underwent multidetector CT before elective VSARR for annuloaortic ectasia with tricuspid aortic valve. The geometries of their aortic roots were measured with a VR-CT workstation. The mean values of geometric height (GH), free margin length (FML), and commissural height (CH) were 17.2±2.4 mm, 36.0±5.2 mm, and 24.0±4.3 mm, respectively. The right coronary/noncoronary CH was significantly greater than the left coronary/right coronary and left coronary/noncoronary CH. The left coronary cusp had the shortest FML, intercommissural distances (ICD), and smallest central angle. Although the right coronary cusp had the largest values for FML, ICD, and central angle, the right coronary cusp had the lowest GH and EH. The VR-CT measurements strongly correlated with intraoperative alternatives, especially with mean GH (R2=0.75) and left coronary/noncoronary CH (R2=0.79). Furthermore, mean GH was observed to be significantly different among the selected graft size groups; therefore, the preoperative mean GH could play a significant role in graft sizing.

CONCLUSIONS

VR-CT evaluation allows a thorough understanding of aortic root anatomy, which could facilitate VSAAR.

Virtual Dissection: an Educational Technology to Enrich Medical Students' Learning Environment in Gastrointestinal Anatomy Course

Background

Virtual dissection provides a digital experience of medical images to visualize anatomy on touchscreen tables. This study aimed to integrate the virtual dissection table (VDT) into the gastrointestinal anatomy course and assess medical students' intended learning outcomes and satisfaction with this educational technology.

Methods

This quasi-experimental study enrolled second-year undergraduate medical students who studied anatomical sciences in the autumn semester of 2021-2022 at a single medical school. In the intervention and control groups, the participants were randomized to study anatomy by VDT or topographical anatomy textbooks. The knowledge tests evaluated the students' learning outcomes of gastrointestinal anatomy, and following the course, students completed a satisfaction survey.

Results

The findings indicated that a significant gain occurred, and instructional intervention during which the learning environment was enriched with virtual dissection could enhance the students' learning (F = 13.33, df = 2, P < 0.01, partial η2 = 0.20) and satisfaction (T = 6.10, df = 54, P < 0.01, Cohen's d = 1.63, CI95% = 1.02-2.23).

Conclusions

This study demonstrates the potential for virtual dissection to augment anatomical science education. Further research is required to consider the contributing features and apply this educational technology to enhance students' anatomy learning.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40670-023-01867-z.

Vulnerability of the ventricular conduction axis during transcatheter aortic valvar implantation: A translational pathologic study

The ventricular components of the conduction axis remain vulnerable following transcatheter aortic valvar replacement. We aimed to describe features which may be used accurately by interventionalists to predict the precise location of the conduction axis, hoping better to avoid conduction disturbances. We scanned eight normal adult heart specimens by 3T magnetic resonance, using the images to simulate histological sections in order accurately to place the conduction axis back within the heart. We then used histology, tested in two pediatric hearts, to prepare sections, validated by the magnetic resonance images, to reveal the key relationships between the conduction axis and the aortic root. The axis was shown to have a close relationship to the nadir of the right coronary leaflet, in particular when the aortic root was rotated in counterclockwise fashion. The axis was more vulnerable in the setting of a narrow inferoseptal recess, when the inferior margin of the membranous septum was above the plane of the virtual basal ring, and when minimal myocardium was supporting the right coronary sinus. The features identified in our study are in keeping with the original description provided by Tawara, but at variance with more recent accounts. They suggest that the vulnerability of the axis during transcatheter valvar replacement can potentially be inferred on the basis of knowledge of the position of the aortic root within the ventricular base. If validated by clinical studies, our findings may better permit avoidance of new-onset left bundle branch block following transcatheter aortic valvar replacement.

Evaluation of aortopulmonary window using virtual dissection of multidetector computed tomography angiography data sets

AIM

The present study sought to evaluate the morphology and associated cardiovascular anomalies in patients with aortopulmonary window on virtual dissection of multidetector computed tomography (CT) angiography data sets.

MATERIAL AND METHODS

We conducted a retrospective search of our departmental database from January 2014 to September 2021 to identify patients with aortopulmonary window and relevant information was extracted from the electronic case records and from routine examination as well as virtual dissection of CT data sets.

RESULTS

An aortopulmonary window was observed in 26 patients (20 males; 6 females). Based on location of the defect, a distal aortopulmonary window was the most common subtype, seen in 13/26 (50%) patients followed by a proximal, complete and intermediate subtypes seen in 7/26 (27%), 5/26 (19%) and 1/26 (4%) patients respectively. Associated ventricular septal defect was observed in 9/26 (34.6%) patients while an interrupted aortic arch was present in 5/26 (19.2%) patients. Tetralogy of Fallot was seen in 5/26 (19.2%) patients. Anomalous origin of right pulmonary artery from ascending aorta and crossed pulmonary arteries were seen in 2/26 (7.6%) patients each. An isolated aortopulmonary window without any simple/complex congenital anomaly was seen in 10/26 (38.5%) patients.

CONCLUSION

Aortopulmonary window is associated with a wide gamut of cardiovascular lesions, with ventricular septal defect being the commonest associated anomaly followed by tetralogy of Fallot and interrupted aortic arch respectively. Virtual dissection of multidetector CT angiography allows detailed anatomical evaluation of aortopulmonary window, allowing a clear visualization of the defect and associated cardiovascular anomalies.

Ex-vivo aortic root and coronary artery cast measurement to validate the accuracy of virtual imaging

BACKGROUND AND AIM OF THE STUDY

To investigate the accuracy of two methods of measuring features in cardiac anatomy, using an objective standard cast model.

METHODS

We made a silicone cast using a swine heart. Computerized tomography data of the solidified cast were processed through virtual reality (VR) software and through two-dimensional multiplanar-reconstruction (2D-MPR), and all measurements were compared against physical measurements of the cast.

RESULTS

The cast perfectly demonstrated the fine detail of the aortic valve and the proximal parts of coronary arteries. Anatomical features were measured by 3D-VR, 2D-MPR, and directly on the cast. Measurement differences between 2D-MPR and the cast were on average at least 3.6 times larger than those between 3D-VR and the cast.

CONCLUSIONS

Based on the observed accuracy, 3D-VR measurements seem considerably more accurate than the current standard 2D-MPR, and 3D-VR may be considered as the next gold standard for 3D measurement of cardiac anatomy in vivo.

Stereogram of the Living Heart, Lung, and Adjacent Structures

Innovations in invasive cardiovascular diagnostics and therapeutics, not only limited to transcatheter approaches but also involving surgical approaches, are based on a precise appreciation of the three-dimensional living heart anatomy. Rapid advancements in three-dimensional cardiovascular imaging technologies in the 21st century have supported such innovations through the periprocedural assessment of the clinical anatomy of the living heart. However, even if high-resolution volume-rendered images are reconstructed, they cannot provide appropriate depth perception when displayed and shared on a two-dimensional display, which is widely used in clinical settings. Currently, images reconstructed from clinical datasets can visualize fine details of the cardiovascular anatomy. Therefore, this is an optimal time for cardiologists and cardiac surgeons to revisit the classic technology, stereopsis, and obtain bonus information from carefully reconstructed clinical images. Using anaglyphs or cross/uncross-fusion of paired images, striking depth perception can be readily obtained without the need for expensive equipment. This conventional technique, when applied to high-resolution volume-rendered images, may help in obtaining appropriate diagnostics, choosing optimal therapeutics, securing procedural success, and preventing complications. Furthermore, it can be used for anatomical education. In this review, we demonstrate multiple stereoscopic images reconstructed from cardiac computed tomographic datasets and discuss their clinical and educational implications.

Living Anatomy of the Pericardial Space: A Guide for Imaging and Interventions

The pericardium of the human heart has received increased attention in recent times due to interest in the epicardial approach for cardiac interventions to treat cardiac arrhythmias refractory to conventional endocardial approaches. To support further clinical application of this technique, it is fundamental to appreciate the living anatomy of the pericardial space, as well as its relationships to the surrounding structures. The anatomy of the pericardial space, however, is extremely difficult regions to visualize. This is due to its complex 3-dimensionality, and the "potential" nature of the space, which becomes obvious only when there is collection of pericardial fluid. This potential space, which is bounded by the epicardium and pericardium, can now be visualized by special techniques as we now report, permitting appreciation of its living morphology. Current sources of knowledge are limited to the dissection images, surgical images, and/or illustrations, which are not necessarily precise or sufficient to provide relevant comprehensive anatomical knowledge to those undertaking the epicardial approach. The authors demonstrate, for the first time to their knowledge, the 3-dimensional living anatomy of the pericardial space relative to its surrounding structures. They also provide correlative anatomy of the left sternocostal triangle as a common site for subxiphoid access. The authors anticipate their report serving as a tool for education of imaging and interventional specialists.

Anaglyph stereo virtual dissection: a novel inexpensive method for stereoscopic visualisation of intracardiac anatomy on CT angiogram

Three-dimensional visualisation is invaluable for evaluating cardiac anatomy. Patient-specific three-dimensional printed models of the heart are useful but require significant infrastructure. The three-dimensional virtual models, derived from 3D echocardiography, computed tomographic (CT) angiography or cardiac magnetic resonance (CMR), permit excellent visualisation of intracardiac anatomy, but viewing on a two-dimensional screen obscures the third dimension. Various forms of extended reality, such as virtual reality and augmented reality, augment the third dimension but only using expensive equipment. Herein, we report a simple technique of anaglyph stereoscopic visualisation of three-dimensional virtual cardiac models. The feasibility of achieving stereovision on a personal computer, using open-source software, and the need for inexpensive anaglyph glasses for viewing make it extremely cost-effective. Further, the retained depth perception of resulting stereo images in electronic and printed format makes sharing with other members of the team easy and effective.

Understanding the Aortic Root Using Computed Tomographic Assessment: A Potential Pathway to Improved Customized Surgical Repair

There is continued interest in surgical repair of both the congenitally malformed aortic valve, and the valve with acquired dysfunction. Aortic valvar repair based on a geometric approach has demonstrated improved durability and outcomes. Such an approach requires a thorough comprehension of the complex 3-dimensional anatomy of both the normal and congenitally malformed aortic root. In this review, we provide an understanding of this anatomy based on the features that can accurately be revealed by contrast-enhanced computed tomographic imaging. We highlight the complimentary role that such imaging, with multiplanar reformatting and 3-dimensional reconstructions, can play in selection of patients, and subsequent presurgical planning for valvar repair. The technique compliments other established techniques for perioperative imaging, with echocardiography maintaining its central role in assessment, and enhances direct surgical evaluation. This additive morphological and functional information holds the potential for improving selection of patients, surgical planning, subsequent surgical repair, and hopefully the subsequent outcomes.

Lacunae regarding dearth of dissection-based teaching during COVID-19 pandemic: how to cope with it?

Introduction

In view of the ongoing COVID-19 pandemic, anatomy education programs were amended so as to shift to primarily online mode from physical classes. In the whole process, main concern area that has emerged is regarding dearth of physical human dissection sessions. There is enough evidence available in literature to suggest that dissection room is an ideal place to cultivate and inculcate discipline independent skills or humanistic skills among the students. These include attributes in relation to ethical practice, professionalism, communication skills, empathy and compassion. Imbibing these skills are an essential element of medical education curriculum as it is desirable that students exhibit these traits when they begin medical practice. Hence deficiency in terms of exposure to physical dissection sessions can adversely affect training of medical students on a long term.

Methods

A literature search of relevant, peer-reviewed, published articles was undertaken from indexed databases (Medline and PubMed, Scopus, Embase, CINAHL Plus, Web of Science and Google Scholar) for this study.

Results

To counter the pertinent issue in online anatomy teaching program, a few measures have been suggested in this paper based on identification of actual deficit areas in terms of learning and analysis thereof. Live streaming of real time dissection, awareness sessions on human dissection, online interactive learning sessions and reflective thoughts-based exercise can contribute to building discipline independent skills in present scenario.

Conclusion

Incorporation and implementation of these interventions within the realm of online anatomy education programs during COVID-19 pandemic can possibly contribute towards desirable learning outcomes.

Three-dimensional visualization of the bovine cardiac conduction system and surrounding structures compared to the arrangements in the human heart

In the human heart, the atrioventricular node is located toward the apex of the triangle of Koch, which is also at the apex of the inferior pyramidal space. It is adjacent to the atrioventricular portion of the membranous septum, through which it penetrates to become the atrioventricular bundle. Subsequent to its penetration, the conduction axis is located on the crest of the ventricular septum, sandwiched between the muscular septum and ventricular component of the membranous septum, where it gives rise to the ramifications of the left bundle branch. In contrast, the bovine conduction axis has a long non-branching component, which penetrates into a thick muscular atrioventricular septum having skirted the main cardiac bone and the rightward half of the non-coronary sinus of the aortic root. It commonly gives rise to both right and left bundle branches within the muscular ventricular septum. Unlike the situation in man, the left bundle branch is long and thin before it branches into its fascicles. These differences from the human heart, however, have yet to be shown in three-dimensions relative to the surrounding structures. We have now achieved this goal by injecting contrast material into the insulating sheaths that surround the conduction network, evaluating the results by subsequent computed tomography. The fibrous atrioventricular membranous septum of the human heart is replaced in the ox by the main cardiac bone and the muscular atrioventricular septum. The apex of the inferior pyramidal space, which in the bovine, as in the human, is related to the atrioventricular node, is placed inferiorly relative to the left ventricular outflow tract. The bovine atrioventricular conduction axis, therefore, originates from a node itself located inferiorly compared to the human arrangement. The axis must then skirt the non-coronary sinus of the aortic root prior to penetrating the thicker muscular ventricular septum, thus accounting for its long non-branching course. We envisage that our findings will further enhance comparative anatomical research.