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Palacios Mini-invasive Surg 2020;4:73 I http://dx.doi.org/10.20517/2574-1225.2020.72 Page 13 of 24

technique. PMV resulted in a substantial decrease in trans mitral gradient and an increase in MVA from
2
2
0.9 cm to 3.5 cm . Table 2 depicts changes in mitral valve area after PMV from different institutions with
large PMV series.
The predictors of the immediate results of PMV are multifactorial. In addition to the morphological
factors, preoperative variables (such as age, history of previous surgical commissurotomy, New York Heart
Association functional class of heart failure, smaller initial mitral valve area, and presence of tricuspid
regurgitation), and procedural factors (such as the non-use of Inoue technique) have been identified as
independent predictors of poor immediate results of PMV [6,10,15,16] .

MECHANISM OF PMV
The mechanism of successful PMV is splitting of the fused commissures toward the mitral annulus,
resulting in commissural widening. This mechanism has been demonstrated by pathologic, surgical, and
echocardiographic studies [7,12,42,43] . In addition, in patients with calcific mitral stenosis, the balloons could
increase mitral valve flexibility by the fracture of the calcified deposits in the mitral valve leaflets. Although
rare, undesirable complications, such as leaflets tears, left ventricular perforation, tear of the atrial septum,
[44]
and rupture of chordae, mitral annulus, and papillary muscle, could also occur .

RISKS AND COMPLICATIONS
The failure rates range from 1% to 15%, and they reflect primarily the learning curve of the
operators [8,9,12,16,37] . Table 3 depicts rate of complications from PMV from different centers with high volume
of PMV. Procedural mortality ranges from 0% to 3%. The incidence of hemopericardium varies from 0.5
to 12%. Embolism is encountered in 0.5% to 5% of cases. Severe mitral regurgitation is the most worrying
complication [21,25,26,37] . It occurs in 2% to 10% of patients and results from non-commissural leaflet tearing,
primarily in cases with unfavorable anatomy, and even more so if there is a heterogeneous distribution
of the morphological abnormalities [25,26] . Surgery is often necessary later and can be conservative in cases
with less severe valve deformity. Although urgent surgery is seldom needed for complications (< 1% in
experienced centers), it may be required for massive hemopericardium or, less frequently, for severe
mitral regurgitation, leading to hemodynamic collapse or refractory pulmonary edema. Immediately after
PMV, color Doppler echo shows small interatrial shunts in most patients. PMV is associated with a 15%
incidence of left-to-right shunt immediately after the procedure. The pulmonary-to-systemic flow ratio is <
1.5:1 in the majority of the patients. The incidence of left-to-right shunt through the atrial communication
[45]
[45]
is greater in patients with echocardiographic scores > 8 . Casale et al. reported the results of post-PMV
left to right shunting in 150 patients who underwent PMV at the Massachusetts General Hospital. A left to
[46]
right shunt through the created atrial communication was present in 28 patients (19%) after PMV . The
pulmonary to systemic flow ratio was > 2:1 in 4 patients and < 2:1 in 24. Univariate predictors of left to right
shunting after valvuloplasty included older age (P < 0.01), lower cardiac output before mitral valvuloplasty
(P < 0.01), higher New York Heart Association functional class before PMV (P < 0.05), presence of mitral
valve calcification under fluoroscopy (P < 0.01) and higher Echo-Score (P < 0.05). Multiple stepwise logistic
regression analysis identified the presence of mitral valve calcification (P < 0.02) and lower cardiac output
(P < 0.02) as independent predictors of a left to right shunt through the atrial communication after PMV.
A persistent atrial septal defect was demonstrated by oximetry in only 5 of 13 patients who underwent
elective right heart catheterization at 11 ± 1 months after mitral valvuloplasty. Doppler color flow echo
cardiography demonstrated a left to right shunt in only one of the remaining three patients who did
not undergo catheterization. Thus, 13 (59%) of 22 patients who had a left to right shunt after PMV were
demonstrated to have no evidence of residual left to right shunt through the created atrial communication
[45]
at 10 ± 1-month follow-up study .