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Echarte-Morales et al. Vessel Plus 2021;5:54 https://dx.doi.org/10.20517/2574-1209.2020.105 Page 7 of 13

[36]
Despite these technical challenges, Avenatti et al. did not find significant differences in procedural time or
outcomes in 12 patients undergoing PMVR after MVr compared to 54 subjects who received MitraClip to
treat to native MR. Although available evidence is limited to small registries, PMVR appears to be a safe and
effective alternative to conventional surgery in patients with MR recurrence after MVr. In this setting,
patient selection may be particularly important, with special focus on preprocedural transmitral gradient
and MV area, echocardiographic window, remaining mobile tissue of both leaflets, the presence of ring
dehiscence or rupture, and the mechanism of MR recurrence .
[31]

Transcatheter mitral valve replacement
Mitral ViV and ViR techniques are based on the implant of dedicated transcatheter prosthesis for the aortic
and pulmonary valves in the MV position, with anchoring at previous surgical prosthesis or annuloplasty
[37]
ring, respectively [Figures 2 and 3]. The transapical route was the first access used for TMVR; however,
the transseptal approach is gaining popularity with the introduction of the third and fourth generation of
percutaneous prosthetic valves. Compared to transeptal access, the transapical route is associated with a
higher incidence of bleeding, respiratory and infectious complications, and a longer recovery period after
[39]
[38]
the procedure . Moreover, TMVR through the femoral vein may reduce periprocedural mortality .
Different transcatheter prosthesis have been used for mitral VIV or ViR implantation, including balloon-
expandable MELODY (Medtronic, Minneapolis, MN, USA) and SAPIEN valves (Edwards Lifesciences,
Irvine, CA, USA), mechanically expandable LOTUS valve (Boston Scientific, Marlborough, MA, USA), and
inflatable prosthetic heart valve DIRECTFLOW (Direct Flow Medical, Inc., Santa Rosa, CA). To date,
balloon expandable SAPIEN valve is by far the most commonly used device and the one with the largest
reported evidence. Cheung et al. analyzed short- and long-term outcomes of 23 patients with severe
[40]
mitral bioprosthetic valve dysfunction (39.1% MR, 26.1% mitral stenosis, and 34.8% both) undergoing
transapical ViV due to high risk for redo MVS (STS score 12.1% ± 6.8%). A SAPIEN valve was successfully
implanted in all patients leading to a significant reduction in transvalvular MV gradient and clinical
improvement, with no significant residual MR. At 30 days, all patients were alive, although one patient
presented a stroke and six subject had major bleeds during hospitalization. During a median follow up of
over two years, survival was 90.4%. One patient needed an early percutaneous reintervention due to atrial
migration of the transcatheter valve . More recently, Whisenant et al. evaluated one-year outcomes in
[40]
[39]
1529 patients undergoing SAPIEN 3 mitral ViV replacement. Procedural technical success was achieved in
96.8% of the cohort and LV outflow tract (LVOT) obstruction was documented in 0.9% of cases. All-cause
mortality was 5.4% and 16.7% at 30 days and 1 year, respectively, and, at 12-month follow-up, over 90% of
patients were in NYHA functional Class I or II.

Compared to ViV procedures, ViR is related to worse outcomes, including lower rates of technical success
and higher rates of device embolization, residual MR, LVOT obstruction, and all-cause mortality [41,42] . The
incidence of recurrent MR after ViR can be over 10%, and it is associated with the incidence of MAE,
including death, stroke, or hemolytic anemia [43,44] . The following features were identified as independent
predictors of this serious complication in patients undergoing TMVR: an anterior leaflet length > 20 mm, a
small native LVOT (< 18 mm), an aorto-mitral annular angle < 115°, a reduced ventricular cavity (left
ventricular end-diastolic diameter < 48 mm), a significant septal bulge, and a predicted neo-LVOT
≤ 1.7 cm 2[45,46] . Two interventional techniques have been described to prevent this major problem in selected
cases with good outcomes: the laceration of the anterior MV leaflet and alcohol septal ablation [47,48] .

Yoon et al. evaluated outcomes in 248 patients who underwent TMVR (ViV and ViR in 176 and 72
[43]
patients, respectively). The indications for procedure were degenerated bioprosthesis and failed