TMVR – Transcatheter Mitral Valve Replacement
TMVR, also known as transcatheter mitral valve replacement is a way of replacing the mitral valve in the heart without the need for conventional open-heart surgery. TMVR transcatheter mitral valve replacement is a treatment for mitral valve stenosis (tight mitral valve) or mitral valve regurgitation (leaky mitral valve) or a mix of the two. TMVR transcatheter mitral valve replacement was developed initially as a method of replacing the mitral valve in patients considered too high risk for surgery but will likely replace mitral valve replacement surgery in the future as the technology improves and the outcomes are proved.
TMVR – Dedicated Transcatheter Mitral Valve Replacement Systems
In the last few years there has been a flurry of activity by major device companies to acquire and advance transcatheter mitral valve replacement technology companies and move the field of TMVR from concept to reality. There are now a number of valves in trials that have been developed specifically for the mitral valve space. The challenges that face transcatheter mitral valve replacement are much greater than those of the aortic valve simply because the mitral valve is such a complex structure. Early results are very promising however and the challenges appear to be surmountable.
Current transcatheter mitral valve replacement TMVR systems that have been implanted in humans include:
Tendyne / Intrepid / Fortis / Navigate / CardiaQ / Tiara
These TMVR valves are all still in their relative infancy and only available in the setting of clinical trials. It will be a few years before the impact and success of these valves is known.
TMVR – Transseptal vs. Transapical Access vs. Transatrial Access
Transseptal access is performed through the femoral vein of the leg and is the least invasive of all the implantation methods. No surgical access is required and the recovery time is fast. Technical expertise is required and the transseptal approach for transcatheter mitral valve replacement is technically challenging as compared to other approaches. Transseptal approaches are widely used in a number of cardiac procedures in addition to TMVR, including watchman device and Mitraclip procedure.
Transapical access involves a small surgical incision on the chest wall on the left hand side through which a valve is passed up in to the mitral position. Advantages of this approach to TMVR include much easier valve positioning. The major disadvantage is a direct cardiac incision and related complications. Many of the current options for dedicated transcatheter mitral valve replacement devices use the transapical approach however it is most likely that over time this transitions toward transseptal delivery.
Transatrial access is more involved than the other approaches and is similar in many ways to a standard cardiac surgical approach. See the robotic approach for a description.
TMVR – Hybrid Robotic Approach
Princeton Baptist Medical Center, Birmingham, Alabama is a pioneer of this approach of transcatheter mitral valve replacement. Using the surgical robot small ports is used to obtain access to the right atrium chamber of the heart for the TMVR. The anterior leaflet of the mitral valve is resected and then under direct visualization a transcatheter valve is placed in position then inflated. Stitches are placed to prevent leak and allow fixation of the valve. The disadvantage of this approach is the need for cardiac bypass and surgical technique. The major advantages are elimination of leak and stabilization and direct positioning of the valve.
TMVR – Transcatheter Mitral Valve In Prosthetic Valve Procedures
Transcatheter Mitral Valve In Prosthetic Valve procedures are where a transcatheter valve is placed inside an existing surgically implanted mitral tissue valve. Prosthetic heart valves can either fail by becoming too tight (prosthetic mitral stenosis) or too leaky (prosthetic mitral regurgitation). The two main access sites for this form of TMVR are transapical and transseptal. For those with the technical ability, transseptal is associated with a much faster recovery. In general these procedures as with other transcatheter mitral valve replacement procedures are reserved for patients who are considered high risk for standard cardiac surgery. Outcomes of transcatheter mitral valve in valve procedures are considered promising and acceptable.
TMVR – Transcatheter Mitral Valve In Ring Procedures
Mitral rings are used as part of a standard surgical mitral valve repair procedure. In mitral valve in ring procedures a transcatheter mitral valve is placed inside a failing ring repair. The treatment is usually for mitral valve regurgitation for failed repair. TMVR Transcatheter mitral valve in ring procedures are much more technically difficult and unpredictable as compared to transcatheter mitral valve in valve procedures. The two main access sites for this form of TMVR are transapical and transseptal. Transapical is much more common however transseptal is becoming much more common. The outcomes of transcatheter mitral valve in ring procedures are worse than valve in valve procedures with higher risk of complications including outflow tract obstruction, valve malpositioning and valve embolization. All of these are potentially lethal complications of TMVR that can necessitate emergent surgical intervention.
TMVR – Transcatheter Mitral Valve In MAC Procedures
MAC is short for mitral annular calcification and describes the process whereby the mitral valve is infiltrated by calcium. The bad news here is that the calcium can lead to failure of the valve that often becomes tight or leaky. The MAC however can act as an anchor point for the placement of a transcatheter mitral valve. The main access sites are transapical, transseptal or transatrial. The outcomes data for mitral valve in MAC are limited and the complication rate can be significant. Complications including outflow tract obstruction, valve malpositioning and valve embolization may occur. In the future, the dedicated TMVR transcatheter mitral valve replacement systems are likely to be the treatment of choice here.