Transcatheter Mitral Valve Replacement
Multiple studies acknowledge that surgical repair of the MV is the
preferred method of management in both primary and secondary MR,
however, not all patients qualify for it.7,13,27,31.
Transcatheter mitral valve replacement (TMVR) is a relatively new
therapy, a little over 500 patients receiving it to date worldwide. It
is not as advanced as transcatheter aortic valve replacement due to the
complexity of the MV and its anatomical structure: asymmetric annulus,
intricate subvalvular apparatus, and located in close proximity to the
left ventricle, subsequently being affected by changes in the left
ventricular function.49
Similar to transcatheter MV repair, TMVR is accomplished using TEE
guidance. In early studies, a left mini-thoracotomy was required to gain
access to the left ventricle. Once inside, the device is directed up to
the left atrium and aligned over the mitral annulus. A specific target
area is identified and the new valve will be deployed, while the
delivery system will be retracted.50 Most of TMVR
procedures still use this technique, as only 4 reported devices were
technically successful using a transfemoral-transseptal approach, the
first-in-human trial using the Sapien M3 valve publishing its results in
2019. Ten patients received the procedure and success was recorded in
nine of them (one patient reported recurrent MR due to paravalvular
leak).51,52
The valves can be mechanical or bioprosthetic and around 70% of
patients who undergo mitral valve replacement will receive a
bioprosthetic valve. Conversely, mechanical valves are believed to be
more resilient as multiple studies report a much lower mortality rate,
despite the need for anticoagulation therapy.31,53,54The same studies, however, highlighted the worryingly high rates of
complications and postoperative mortality. Systematic reviews place the
mortality rate anywhere between 10 to 60% after one year, while the
risk of developing heart failure can be as high as
31%.49,51,53,55 Tendyne prosthesis (Abbott
Structural, Santa Clara the US) is the first TMVR device to gain CE
approval in January 2020, but the evolution of TMVR systems is far from
rapid, due to the strict selection criteria of ongoing clinical trials,
which affect results by diminishing the external validity of the studies
and their transferability to real-life clinical scenarios
.49,51