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Nappi et al. Vessel Plus 2021;5:40 https://dx.doi.org/10.20517/2574-1209.2021.06 Page 3 of 20

TMViV or the TMViR technique [12-19] . This type of approach can be considered a safe alternative to reduce
[12]
the risk of operative mortality and increase the clinical benefit in patients experiencing heart failure (HF) .
Reoperation for previous mitral repair failure or prosthesis degeneration can be performed via a second
sternotomy or through a right thoracotomy approach [20-22] . The intraoperative risk assessment of a
resternotomy is evaluated by thoracic CT and coronary or graft catheterization. Cardiopulmonary bypass
(CPB) will be established using the femoral vessels and the sternum will be reopened using an oscillating
saw. The right thoracotomy instead will be performed by making an incision on the right infra-mammary
fold, isolating the right lung and opening the pericardium anterior to the right phrenic nerve, which will be
isolated and protected so as to allow safe surgical access to the left atrium [20,23-25] .

Despite the lack of established guidelines to choose the safest therapeutic approach and the presence of
established evidence related to surgical approaches, the recent feasibility results for transcatheter mitral
valve-in-valve procedures place the treatment of structural heart disease into a novel prospective with
evidence [13-16] .

We undertake this review with the primary goal to reassume the existing evidence for the use of
transcatheter mitral valve procedures or when repeat reoperative mitral valve surgery is required. We focus
on the recent results from prospective registry studies, propensity matched observational series, meta-
analyses and unmatched observational series. Our secondary objective is to identify a pool of patients for
whom the benefits of the transcatheter mitral valve (TMViV) and ring valve (TMViR) procedure are more
evident than standard redo surgical therapy [5-7,12,13] .

With the aim to encourage a broader use of transcatheter mitral valve-in-valve implantation and provide
drive for health professionals, we herein argue the current evidence for the choice of the various
transcatheter mitral valve-in-valve therapies (TMViV-T). Finally, we develop a useful evidence-based
algorithm to guide the choice of the mitral valve prosthesis in case of reoperation.

The emerging new contribution of transcatheter mitral valve-in-valve therapy
TMViV-T is presently considered in the United States and Europe for the management of deteriorated MV
(TMViV) or mitral ring (TMViR) prostheses in patients at high risk for standard surgical approach [17,18] .

Unlike Mitraclip therapy, in which the legislative endorsement is based on the results reported from the
[19]
Endovascular Valve Edge-to-Edge Repair randomized Study (EVEREST) , there is poor evidence on the
survival benefit in patients who have undergone TMViV/TMViR for deteriorated bioprostheses compared
to those who had redo surgery for SVD of MV [3,14,15,17,19] .

Both procedures had the same enrollment method for the patients who were considered suitable for the use
of devices, therefore 349 persons from 98 sites were included in the US registry from 2013 to 2015 .
[26]
Nevertheless, the recent literature shows that the transcatheter procedure with the use of Mitraclip has a
slight advantage over TMViV-T due to a better understanding of the pathophysiology of mitral
rigurgitation and the normalization of the geometry [2-4,8,9,27-30] .

Recipients of transcatheter mitral valve implant (n = 248) were treated for degenerated mitral valve
prosthesis (TMViV 76.1%) or severe mitral regurgitation occurring after a mitral valve repair using annular
ring (TMViR 23.9%). The population recruited in the TMViV-T group was at high risk for conventional
open mitral valve operation, with a median age of 76 years and being predominantly female (61%) [18,26] .