Transcatheter mitral valve replacement: an evolution of a revolution

Role of computed tomography in transcatheter replacement of 'other valves': a comprehensive review of preprocedural imaging

Transcatheter procedures for heart valve repair or replacement represent a valid alternative for treating patients who are inoperable or at a high risk for open-heart surgery. The transcatheter approach has become predominant over surgical intervention for aortic valve disease, but it is also increasingly utilized for diseases of the 'other valves', that is the mitral and, to a lesser extent, tricuspid and pulmonary valve. Preprocedural imaging is essential for planning the transcatheter intervention and computed tomography has become the main imaging modality by providing information that can guide the type of treatment and choice of device as well as predict outcome and prevent complications. In particular, preprocedural computed tomography is useful for providing anatomic details and simulating the effects of device implantation using 3D models. Transcatheter mitral valve replacement is indicated for the treatment of mitral regurgitation, either primary or secondary, and computed tomography is crucial for the success of the procedure. It allows evaluating the mitral valve apparatus, the surrounding structures and the left heart chambers, identifying the best access route and the landing zone and myocardial shelf, and predicting obstruction of the left ventricular outflow tract, which is the most frequent postprocedural complication. Tricuspid valve regurgitation with or without stenosis and pulmonary valve stenosis and regurgitation can also be treated using a transcatheter approach. Computer tomography provides information on the tricuspid and pulmonary valve apparatus, the structures that are spatially related to it and may be affected by the procedure, the right heart chambers and the right ventricular outflow tract.

Transcatheter mitral valve replacement

Transcatheter mitral valve (MV) repair, specifically the edge-to-edge leaflet repair, is a less invasive treatment of symptomatic mitral regurgitation (MR) in patients with high or prohibitive surgical risk. In cases with severe leaflet calcification, small mitral orifice area, and/or extremely wide regurgitation across the entire MV commissure, transcatheter MV repair may rather cause suboptimal or potentially hazardous outcomes. In these cases, MV replacement can be a more suitable option. Recently, percutaneous transcatheter MV replacement has emerged as an acceptable therapeutic option for the treatment of degenerated surgical bioprosthetic disease. Moreover, several transcatheter devices for native MV replacement are under evaluation with a hope to provide more complete and reproducible restoration of MV function. In this article, we will review current status, applications, clinical outcomes, and limitations that need to be overcome for transcatheter MV replacement for both degenerated surgical bioprosthetic disease and native MV disorders.

Cardiac prostheses-related hemolytic anemia

Hemolysis is an unintended sequel of temporary or permanent intracardiac devices. However, limited data exist on the characteristics and treatment of hemolysis in patients with cardiac prostheses. This entity, albeit uncommon, often poses significant diagnostic and management challenges to the clinical cardiologist. In this article, we aim to provide a contemporary overview of the incidence, mechanisms, diagnosis, and management of cardiac prosthesis‐related hemolysis.

Transcatheter Mitral Valve Planning and the Neo-LVOT: Utilization of Virtual Simulation Models and 3D Printing

PURPOSE OF REVIEW

Transcatheter mitral valve replacement (TMVR) is an emerging alternative for patients with severe mitral valve regurgitation who are considered at high risk for conventional surgical options. The early clinical experience with TMVR has shown that pre-procedural planning with computed tomography (CT) is needed to mitigate the risk of potentially lethal procedural complications such as left ventricular outflow tract (LVOT) obstruction. The goal of this review is to provide an overview of key concepts relating to TMVR pre-procedural planning, with particular emphasis on imaging-based methods for predicting TMVR-related LVOT obstruction.

RECENT FINDINGS

Risk of LVOT obstruction can be assessed with CT-based pre-procedural planning by using virtual device simulations to estimate the residual 'neo-LVOT' cross-sectional area which remains after device implantation. A neo-LVOT area of less than 2 cm² is currently thought to increase the risk of obstruction; however, additional studies are needed to further validate this cutoff value. Three-dimensional printing and personalized computational simulations are also emerging as valuable tools which may offer insights not readily confered by conventional two-dimensional image analysis. The simulated neo-LVOT should be routinely assessed on pre-procedural CT when evaluating anatomical suitability for TMVR.

Contemporary outcomes of isolated bioprothestic mitral valve replacement for mitral regurgitation

Background

Early experience with transcatheter mitral valve replacement (TMVR) highlighted several investigational challenges related to this novel therapy. Conclusive randomised clinical trials in the field may, therefore, be years ahead. In the interim, contemporary outcomes of isolated surgical bioprosthetic mitral valve replacement (MVR) can be used as a benchmark for the emerging TMVR therapies.

Methods

We used the nationwide inpatient sample to examine recent trends and outcomes of surgical bioprosthetic MVR for mitral regurgitation (isolated and combined).

Results

21 007 patients who had bioprosthetic MVR between 2003 and 2014 were included. Of those, 30% had isolated MVR and 70% had concomitant cardiac surgical procedure(s). In patients who underwent isolated bioprothestic MVR, mean age was 68±13, and females were the majority (58.4%). Most of these procedures were performed at teaching institutions (71.3%) and during an elective admission (64%). In-hospital mortality improved during the study period (7.8% in 2003 to 4.7% in 2014, p trend=0.016). Postoperative morbidities were common; permanent pacemaker 11.7%, stroke 2.4%, new dialysis 4.9% and blood transfusion 41.6%. Mean length of stay was 13±12 days, and 27.2% of patients were discharged to an intermediate care of rehabilitation facility. Cost of hospitalisation was $62 443±50 997.

Conclusions

Isolated bioprosthetic MVR for mitral regurgitation is performed infrequently but is associated with significant in-hospital morbidity and mortality and cost in contemporary practice. These data are useful as benchmarks for the evolving TMVR therapies.

Degenerative Mitral Stenosis: From Pathophysiology to Challenging Interventional Treatment

Mitral stenosis (MS) is characterized by obstruction of left ventricular inflow as a result of narrowing of the mitral valve orifice. Although its prevalence has declined over the last decade, especially in developed countries, it remains an important cause of morbidity and mortality.  The most often cause of MS worldwide is still postrheumatic mitral valve disease. However, in developed countries, degenerative or calcific changes cause MS in a siginificant proportion of patients. Although the range of treatment for mitral valve disease has grown over the years in parallel with transcatheter therapies for aortic valve disease, these improvements in mitral valve disease therapy have experienced slower development. This is mainly due to the more complex anatomy of the mitral valve and entire mitral apparatus, and the interplay of the mitral valve with the left ventricle which hinders the development of effective implantable mitral valve devices. This is especially the case with degenerative MS where percutaneous or surgical comissurotomy is rarely employed due to the presence of extensive annular calcification and at the base of leaflets, without associated commissural fusion. However, the last few years have witnessed innovations in transcatheter interventional procedures for degenerative MS which consequently hinted that in the future, transcatheter mitral valve replacement could be the treatment of choice for these patients.

Percutaneous Mitral Valve Technology: What Is on the Horizon?

Mitral valve disease is common, with mitral regurgitation (MR) being the most frequent pathology. The etiology of MR is diverse, but, if left untreated, MR results in left ventricular (LV) volume overload, leading to remodeling, dilation of the LV, pulmonary hypertension, heart failure, and death. Mitral regurgitation is a high-risk diagnosis, yet a minority of symptomatic patients are referred for discussion of surgical treatment options. Percutaneous repair options are under development to address this clinical need and emphasize correction of the underlying anatomical pathology to restore mitral valve coaptation. Transcatheter mitral valve replacement is in the early stages of development and may prove safe and effective in certain patient populations. Investigational devices are challenging our current thinking about the management of mitral valve disease, and it will be the task of the multidisciplinary Heart Team to determine the right device for the right pathology.