**5.1. Cardiac perforation and tamponade**

Hemopericardium is the main complication of BMV and is seen in 1% of patients. The transseptal puncture is the source of most cardiac perforations during BMV. The anatomic factors of patients such as atrial enlargement and chest deformities increase the risk. TEE and ICE can guide the transseptal puncture, especially when the operator is inexperienced or in difficult cases, and reduce the risk of hemopericardium. Double-balloon mitral valvuloplasty and metallic commissurotome are associated with the risk of LV perforation because the wires are handled in the LV cavity. The management depends on the severity of pericardial effusion and the mechanism and consists of closed observation, reversal of heparin, pericardiocentesis, and emergent surgery. When the hemopericardium happens after septal dilation or LV perforation, especially if it is retractable despite prompt drainage, surgery is necessary to be proceeded.

#### **5.2. Systemic embolism and stroke**

While BMV might decrease the long-term risk of systemic embolism in patients with MS, the procedure itself can be associated with embolic stroke in about 1–1.5% of patients [28]. Meticulous anticoagulation and de-airing of the equipment and preprocedural TEE to rule out LA thrombi will reduce the chance of systemic embolism. An undiagnosed pre-existing LA/LAA clot and thrombus formation during the procedure are the main mechanisms, but calcium or air embolism also has a role.

#### **5.3. Severe MR**

**Figure 4.** Postprocedural 3D imaging of the mitral valve revealing final mitral valve area of 1.45 cm<sup>2</sup>

Balloon reference size (RS)

108 Interventional Cardiology

Balloon size selection

Inflation mode

Closing criteria

– MVA > 1.5 cm2

– 50% increase in the MVA – 50% fall in mean gradient

– 0.1 × height (cm) + 10 (after rounding the patient's height to the nearest zero) or

– Inter-commissural diameter measured on parasternal short-axis echocardiogram view

– RS-matched if the patient is young, valve is pliable, and MR is absent or less than 1+

– Start 2 mm below the RS in low risk patients, 4 mm in high risk patients

– Inflate in 1 mm increments under echocardiographic guidance

– Fall in mean gradient from >10 mm Hg to <5 mm Hg

MR, mitral regurgitation; MVA, mitral valve area; RS, reference size.

– Appearance or aggravation of MR > 1+ – Complete opening of at least one commissure

**Table 2.** Inoue balloon selection and inflation protocol.

– 1 size smaller than the RS if the valve is rigid, MR is >1+ and in high risk subjects (i.e., pregnancy, old age)

– 30 for height >180 cm, 28 for 160–180 cm, 26 for <160 cm or

.

Commissural opening, which is the main mechanism of increasing the MVA, is associated with aggravating MR after BMV in many patients but most are not significant and usually do not worsen functional status and long-term prognosis of the affected patients. Severe MR occurs in 2–15% of patients mainly because of non-commissural valve tearing and chordal rupture but exaggerated commissural splitting and rarely papillary muscle rupture are responsible [27, 29–31]. The incidence of severe MR does not change with different techniques (Inoue vs. double balloon and metallic commissurotomy) [20, 32]. Unfavorable valve anatomy and inappropriate balloon sizing and inflation protocol predict the occurrence of severe MR after BMV, but their predictive value is not high and it can occur unpredictably in some patients with good morphologic features. Most patients need subsequent mitral valve surgery (mostly MVR) because severe MR is associated with the deterioration of functional status and poor outcomes. The timing of the surgery is determined by clinical tolerance, hemodynamic stability, mechanism of MR, and surgical risk. Most patients with severe MR can be managed conservatively and are subjected to mitral valve surgery on a scheduled basis. In a small number of patients who remain severely symptomatic despite initial medical therapy or who experience hemodynamic instability, or when the mechanical background of MR is severe and irreversible, urgent MVR should be planned. Patients with moderate MR can be often followed-up for a long period of time and some even experience a reduction in the severity of MR over time [33, 34].

#### **5.4. Atrial septal defect**

A wide range of frequency has been reported (10–90%) depending on modality that has been used for detection [35, 36]. Most defects decrease in size or disappear over time and have no adverse effects [37]. Infrequently, the defect is large enough to cause significant left-to-right shunting, especially when there is a significant residual mitral valve gradient and, therefore, surgical repair should be performed along with mitral valve surgery. Percutaneous closure of post-BMV residual atrial septal defects has not been reported and seems to be unsuccessful. In rare circumstances, right-to-left shunting and subsequent paradoxical embolism might happen in patients with significant pulmonary hypertension.

#### **5.5. Emergent surgery**

Rarely, patients need emergent surgery because of the complications. The most frequent cause is hemopericardium unresponsive to pericardiocentesis, especially when it happens after septal dilation and LV perforation. In most patients, the surgery includes repair of the tearing and MVR. Severe MR can also necessitate urgent surgery in some patients.
