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Palacios Mini-invasive Surg 2020;4:73 I http://dx.doi.org/10.20517/2574-1225.2020.72 Page 21 of 24

lower survival and event-free survival (survival with freedom from mitral valve surgery or NYHA class III
[59]
or IV heart failure). Furthermore, Cruz-Gonzalez et al. examined the effect of elevated PVR on PMV
procedural success, short- and long-term clinical outcomes (i.e., mortality, mitral valve surgery, and redo
PMV) in 926 consecutive patients undergoing PMV at the Massachusetts General Hospital. Of the 926
patients, 263 (28.4%) had PVR ≥ 4 Woods units (WU) and 663 (71.6%) had PVR < 4 WU. Patients with
PVR ≥ 4 WU were older and more symptomatic and had worse valve morphology for PMV. The patients
with PVR ≥ 4 WU also had lower PMV procedural success than those with PVR < 4 WU (78.2% vs. 85.6%,
P = 0.006). However, after multivariate adjustment, PVR was no longer an independent predictor of PMV
success nor an independent predictor of the combined end point at a median follow-up of 3.2 years. They
concluded that elevated PVR at PMV is not an independent predictor of procedural success or long-term
outcomes. Therefore, appropriately selected patients with rheumatic mitral stenosis might benefit from
[59]
PMV, even in the presence of elevated pre-procedural PVR .

TRANSCATHETER MVR, A FUTURISTIC PROMISING APPROACH
Mitral annulus calcification (MAC) is another disease that could result in severe mitral stenosis or mixed
mitral valve disease. Patients with MAC are frequently an elderly high-risk population with multiple
comorbidities and a high risk of cardiovascular death and all-cause mortality. The risk of surgical MVR in
patients with severe MAC is high. Transcatheter MVR (TMVR) has recently emerged as an exciting new
frontier in the field of cardiac structural interventions. Results of the earlier experience with TMVR are
encouraging but remain at an early stage [60,61] .

PMV IN PATIENTS WITH STENOSED MITRAL BIOPROSTHESIS
Transcatheter mitral valve-in-valve implantation for dysfunctional biological mitral prosthesis can
be performed with minimal operative morbidity and mortality and favorable midterm clinical and
hemodynamic outcomes. Nowadays, transcatheter valve in valve has a class IIa indication for bioprosthetic
mitral valve degeneration in high-risk to prohibited surgical risk patients according to AHA/ACC 2017
guidelines. However, due to anatomic limitations, not all patients qualify for this procedure and PMV is
still an option with symptomatic and hemodynamic benefit. There have been limited reports of successful
procedures of balloon valvuloplasty for bioprosthetic mitral valve stenosis. However, there is a need for
prospective studies to assess the efficacy and durability of this procedure [62,63] .

CONCLUSION
PMV should be the procedure of choice for the treatment of patients with rheumatic mitral stenosis who
are, from clinical and morphologic points of view, optimal candidates for PMV. Patients with Echo-Sc
≤ 8 have the best results, particularly if they are young, are in normal sinus rhythm, have no pulmonary
hypertension, and have no evidence of calcification of the mitral valve under fluoroscopy. The immediate
and long-term results of PMV in this group of patients are similar to those reported after surgical mitral
commissurotomy. Patients with Echo-Sc > 8 have only a 50% chance to obtain a successful hemodynamic
result with PMV, and long-term follow-up results are worse than those from patients with Echo-Sc ≤ 8. In
patients with Echo-Sc ≥ 12, it is unlikely that PMV could produce good immediate or long-term results.
They preferably should undergo open heart surgery. PMV could be performed in these patients if they
are non- or high-risk surgical candidates. Finally, much remains to be done in refining indications for
patients with few or no symptoms and those with unfavorable anatomy. The question remains as to which
procedure, MVR or PMV, is more suitable for patients with Echo-Sc > 8 but ≤ 12 (the so called the gray
zone). Analysis of the individual component of the Echo-Sc could be helpful in decide to proceed with
PMV over surgery. Severity of leaflet thickening and degree of sub valvular disease would favor MVR, while
mobility and calcification would favor PMV. Surgical therapy for mitral stenosis should be reserved, for
patients who have ≤ 2 + Sellers grade of MR by angiography, and for those patients with severe mitral valve