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What Is a Transcatheter Mitral Valve In Ring (TMVIR) Procedure?
A Transcatheter Mitral Valve in ring procedure, also known as TMVIR, is when a transcatheter valve is placed in to an existing surgically implanted mitral ring to treat a failing mitral valve repair. The TMVIR procedure is used to treat either a leaky or tight mitral valve that has had a prior placed mitral valve repair with placement of a mitral valve ring. The mitral valve in ring procedure is a procedure which is considered part of the transcatheter mitral valve replacement, which along with the TAVR procedure are revolutionizing our approach to heart valve disease.
Transcatheter Mitral Valve In Ring Procedures
Mitral annuloplasty rings are a standard part of mitral valve repair. Failure of prior mitral valve repairs with recurrent regurgitation is common and the prospect of reoperation in this often high-risk group is often daunting. This has led to the development of catheter based or hybrid mitral valve in ring approaches whereby a transcatheter heart valve is placed inside an existing mitral ring that is used as an anchor for the transcatheter heart valve. This is known as a transcatheter mitral valve in ring procedure TMVIR.
Transcatheter mitral valve in ring procedures (TMVIR) requires experience and the infrastructure only seen in mature structural heart programs. Expertise in structural heart intervention, pre and peri procedural imaging, and cardiac surgery are required given the complexity of such procedures.
Access For Transcatheter Mitral Valve In Ring Procedures
Primary methods of access for mitral valve in ring (TMVIR) procedures are
Of course apical and trans-atrial involve surgical associated risks and the downsides of that. Transseptal is a technically harder procedure for many operators but allows avoidance of surgical access and is easier on patient with much faster recovery.
Trans-atrial may have potential for positioning sutures and accurate placement however outcomes data are not great and this is currently limited. In my opinion for valve in ring procedures (particularly valve in full ring) the trans-atrial role is very limited.
Advantages of a transapical access include a ‘straight shot’ to the valve and easier stable positioning. In general transapical access has been the predominant method of implantation worldwide however as technical expertise is growing the transseptal method is becoming more common.
In our program, transseptal access is standard for transcatheter mitral valve in ring TMVIR procedures given our excellent results, experience and comfort with this method and the clear advantages in terms of patient recovery through avoiding the need for any surgical incisions.
Characteristics of Failed Mitral Rings
In transcatheter mitral valve in ring procedures it is critical to understand the characteristics of the surgically implanted ring. Important questions in mitral valve in ring procedures include:
Is the ring a rigid or flexible ring? A flexible ring will allow more likely complete sealing and conform to the expanded valve. A rigid ring will lead to the potential for stent deformation and the lack of conformity may lead to significant paravalvular leak.
Is it a complete or incomplete ring? A complete ring will allow for more likelihood of complete sealing and fixation of the transcatheter valve. An incomplete ring will lead to a much less predictable result and uncertainty regarding anchoring particularly in the absence of annular calcium.
What does the ring look like on fluoroscopy? Fluoroscopy is essentially the primary method of positioning implant thus critical. Some rings are much more visible on fluoroscopy than others.
What is the size / internal diameter of the ring? There should be some degree of oversizing in the choice of implant however excessive oversizing carries a risk of complication also.
What is the optimal implantation target? Typically it is for the final deployment to be 50/50 on the ring.
Type of Transcatheter Valve Used For Mitral Valve In Ring
By far the most commonly used transcatheter mitral valve in ring valve is the Sapien valve. Currently the S3 valve. There are case reports of direct flow, lotus and melody valves being used.
Potential Complications of Transcatheter Mitral Valve In Ring Procedures
Valve Malposition And Embolization
Registries from centers performing the transcatheter mitral valve in ring procedures report that malposition is uncommon and around 10% only, however it must be taken in to account that centers involved have experienced structural heart programs and so are not necessarily generalizable.
Transcatheter mitral valve in ring poses a significant risk for the development of LVOT obstruction. The LVOT is dynamic and the structures involved need to be assessed carefully to select those at high risk. Angles between aortic and mitral planes taken together with chamber size and wall thickness are important. The characteristics, size and redundancy of the anterior leaflet are important also. 3D TTE / TEE and cardiac CT scans are potentially useful also. Ultimately there is no 100% way to predict clinically significant LVOT obstruction however careful decision-making is important. There has been development of novel transcatheter options to lacerate the anterior leaflet potentially decreasing the risk of LVOT obstruction.
TMVIR transcatheter mitral valve in ring procedures risk of paravalvular regurgitation between the valve and the ring, more so with rigid rings that cause valve stent deformation.
Infrastructure Needed For Transcatheter Mitral Valve In Ring Procedures
There is no doubt that mitral valve in ring procedures should only be attempted in a mature structural heart program. Outcomes are far from perfect even in registry settings and patients should not be surgical candidates.
Pre-procedural – For transcatheter mitral valve in ring (TMVIR) procedures heart team approach and imaging expertise is key in case selection, picking up, and avoiding pitfalls such as LVOT obstruction. The characteristics of the valve need to be known to allow for accurate sizing and 3D TEE/CT scan expertise is needed also in this regard for geometric characterization. Availability of free communication with device representatives and strong support is important in our opinion.
Procedural – The room should have appropriate facility for surgical intervention, i.e. a dedicated structural lab or a hybrid lab. In our opinion availability of ECMO or pump is required for transseptal approach in the event of instability for complication such as malpositioning or embolization. For transseptal procedures operators should have a more than basic experience with transseptal itself and the use of typical stiff type guidewire and delivery in to the left heart chambers. Intraprocedural imaging is key with 3DTEE and fluoroscopy.
Brief Literature Review For Transcatheter Mitral Valve In Ring Procedures
In this report, mitral valve in ring procedure led to ring fracture and annular injury. This was likely due to aggressive post-dilation of the ventricular aspect of the valve.
In this report, the use of a dedicated transcatheter mitral valve replacement system in a mitral ring is described.
Short-term outcomes of mitral valve in ring are described in these reports and while they are inferior to valve in valve, they demonstrate acceptable short-term outcomes. In the larger of the studies, 72 patients across many centers underwent mitral valve in ring procedures. Technical success was reported as 83% with 11% needing 2nd valve implantation. 20% had moderate or greater residual MR, 1 year mortality was 29%. There is still a long way to go however before the outcomes of transcatheter mitral valve in ring (TMVIR) can be considered good.
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