Name the Cardiac Device • Xray of the Week
Figure 1. Name the cardiac device.
Figure 2. A: Plain radiograph demonstrating the TMVR (red arrows). Note on the plain xray that the long axis of the TMVR replacement is more horizontal than seen with TAVR B: Axial CT image of the chest showing TMVR (yellow arrows). C: Coronal CT image of the chest showing TMVR (green arrows).
Figure 3. Video demonstrating transapical placement technique for Transcatheter Mitral Valve Replacement (Neovasc).
Figure 4. A: Plain radiograph demonstrating the TAVR (red arrows). Note on the plain xray that the long axis of the TAVR replacement is more vertical than seen with TMVR B: Axial CT image of the chest showing TAVR (green arrow). Note the location of the normal mitral valve (yellow arrows) C: Coronal CT image of the chest showing TAVR (green arrow).
Mitral regurgitation (MR) is the most common type of mitral valve disease in developed nations, and mitral valve disease itself is the second most common valvular heart disease within adults. Untreated MR can lead to systolic and diastolic congestive heart failure (CHF) with an annual mortality rate of 5%. Treatment options for MR include both surgical and minimally invasive approaches. The latter of these approaches includes both the MitraClip (transcatheter mitral valve repair technique or TMVr) or transcatheter mitral valve replacement (TMVR) (Fig. 1-3). Currently only TMVr via MitraClip is FDA approved and thus remains standard of care, but this approach is limited in use due to the small proportion of suitable patients. Unlike the MitraClip, TMVR has been mostly experimental and while over 30 different systems are in development, only a few of these technologies have reached early feasibility studies in humans including but not limited to the Tendyne MV system, Sapien 3 and Highlife Valve. Transeptal, transapical and transfemoral approaches have been used for placement of these prosthetic valves (Fig. 3). All of the valves are comprised of 3 bovine or porcine leaflets in an expandable stentframe (Fig. 3).
Imaging for mitral valve replacement falls into 3 main categories, pre-procedural, intra-procedural, and post-procedure. Due to lack of visualization during transcatheter approaches and the complex anatomical structure of the mitral valveposes a number of additional difficulties that make replacement more complicated than that of the AV. Among these is the fact that the mitral valve lacks the same calcifications, which function as landmarks for fluoroscopy, that AV valves contain make visualization, positioning, and anchoring all the more difficult. Intra-procedural imaging via fluoroscopy is used to ensure proper placement and deployment of the prosthesis. Unfortunately, due to the limitations of fluoroscopy , pre-procedural imaging via 2D echocardiography and angiography are crucial for success. Multidetector CT (MDCT), which provides a 3D reconstruction of the valve allowing for detailed measurements, has gained use in pre-procedural imaging as well. Recent studies have shown that even 3D TEE compared to 2D echo allow for better evaluation and flow convergence. In addition to its complex geometry, the mitral valve in identifying soft tissue structures, imaging will be inadequate in a mitral valve with a lack of calcifications. Thus, TEE also plays a role in intra-procedural imaging as well as immediately following deployment and identifying potential complications such as tamponade, septal rupture, and coronary sinus trauma.
While crossover of Transcatheter Aortic Valve Replacement TAVR technologies and approaches continue to aid in the development of similar TMVR devices, several key differences do exist that limit this. Included within these differences are patient age in that MR patients tend to be much younger than Aortic Stenosis (AS) patients, disease etiology, and the benefit of conservative therapy. Complications of TMVR include left ventricular outflow tract valve displacement, cardiovascular mortality, device malfunction, and stroke. On plain radiographs a TMVR prosthesis can easily be misidentified as a TAVR and that studies have shown that the “imaginary line method” may not be a reliable method of discerning between the two. Rather use of the “valve orifice” or “perceived direction of blood flow” methods should be employed. As seen in this case, CT is definitive in discerning the valve location (Fig. 4).
1. Kelley C, Lazkani M, Farah J, Pershad A. Percutaneous mitral valve repair: A new treatment for mitral regurgitation. Indian Heart J. 2016;68(3):399-404. doi:10.1016/j.ihj.2015.08.025
2. Meng Z, Zhang E-L, Wu Y-J. Current Status and Future Direction of Transcatheter Mitral Valve Replacement. Chin Med J (Engl). 2018;131(5):505-507. doi:10.4103/0366-6999.226080
3. Alkhouli M, Alqahtani F, Aljohani S. Transcatheter mitral valve replacement: an evolution of a revolution. J Thorac Dis. 2017;9(Suppl 7):S668-S672. doi:10.21037/jtd.2017.05.60
4. Ramlawi B, Gammie JS. Mitral Valve Surgery: Current Minimally Invasive and Transcatheter Options. Methodist Debakey Cardiovasc J. 2016;12(1):20-26. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4847963/
5. Foot CL, Coucher J, Stickley M, Mundy J, Venkatesh B. The imaginary line method is not reliable for identification of prosthetic heart valves on AP chest radiographs. Crit Care Resusc. 2006;8(1):15-18. https://www.ncbi.nlm.nih.gov/pubmed/16536714
6. del Val D, Ferreira‐Neto AN, Wintzer‐Wehekind J, et al. Early Experience With Transcatheter Mitral Valve Replacement: A Systematic Review. Journal of the American Heart Association. 2019;8(17):e013332. doi:10.1161/JAHA.119.013332
7. Natarajan N, Patel P, Bartel T, et al. Peri-procedural imaging for transcatheter mitral valve replacement. Cardiovasc Diagn Ther. 2016;6(2):144-159. doi:10.21037/cdt.2016.02.04
Transcatheter Aortic Valve Replacement (TAVR)
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Neal Shah is a medical student at The Edward Via College of Osteopathic Medicine (VCOM)–Carolinas and intends on completing his residency within the field of radiology. Prior to medical school, he completed his undergraduate studies at the University of North Carolina at Chapel Hill where he majored in economics and chemistry. During his 4 years there he worked in UNC’s Biomedical Research Imaging Center where he helped develop formulations for iron-oxide nanoparticles used for MRI; it was here that his love for the field of radiology developed. He eventually wishes to also pursue his MBA and hopes to use it to help advance the field of medicine in terms of medical innovation.
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Kevin M. Rice, MD is the president of Global Radiology CME
Dr. Rice is a radiologist with Renaissance Imaging Medical Associates. and is currently the Vice Chief of Staff at Valley Presbyterian Hospital in Los Angeles, California. Dr. Rice has made several media appearances as part of his ongoing commitment to public education. Dr. Rice's passion for state of the art radiology and teaching includes acting as a guest lecturer at UCLA. In 2015, Dr. Rice and Natalie Rice founded Global Radiology CME to provide innovative radiology education at exciting international destinations, with the world's foremost authorities in their field. In 2016, Dr. Rice was nominated and became a semifinalist for a "Minnie" Award for the Most Effective Radiology Educator.
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