Percutaneous Mitral Balloon Valvuloplasty (Commissurotomy, Valvotomy)

Background

Before 1984, when Inoue et al first described the clinical application of percutaneous mitral balloon valvuloplasty (PMBV) (or percutaneous mitral commissurotomy [PMC], percutaneous mitral valvotomy [PMV]), ^[1] surgical mitral commissurotomy was the preferred option for patients who had severe mitral stenosis (MS). Since its introduction, percutaneous mitral balloon valvuloplasty has demonstrated good immediate and midterm results ^{[2, 3, 4]} and has replaced surgical mitral commissurotomy as the preferred treatment of rheumatic MS in appropriate candidates. ^[5]

The image below depicts mitral stenosis.

Relevant anatomy

The human heart has four valves. The mitral valve connects the left atrium (LA) and the left ventricle (LV). The mitral valve opens during diastole to allow the blood flow from the LA to the LV. During ventricular systole, the mitral valve closes and prevents backflow to the LA. The normal function of the mitral valve depends on its 6 components, which are (1) the left atrial wall, (2) the annulus, (3) the leaflets, (4) the chordae tendineae, (5) the papillary muscles, and (6) the left ventricular wall. For more information about the relevant anatomy, see Mitral Valve Anatomy.

American College of Cardiology/American Heart Association (ACC/AHA) guidelines

Indications for percutaneous mitral balloon valvuloplasty

Class I recommendations

• Transthoracic echocardiography (TTE) is indicated in patients with signs or symptoms of mitral stenosis (MS) to establish the diagnosis, quantify hemodynamic severity (mean pressure gradient, mitral valve area, and pulmonary artery pressure), assess concomitant valvular lesions, and demonstrate valve morphology (to determine suitability for mitral commissurotomy) (level of evidence: B). ^[6]

• Transesophageal echocardiography (TEE) should be performed in patients considered for percutaneous mitral balloon commissurotomy to assess the presence or absence of left atrial thrombus and to further evaluate the severity of mitral regurgitation (MR) (level of evidence: B). ^[6]

• Percutaneous mitral balloon commissurotomy is recommended for symptomatic patients with severe MS (mitral valve area ≤1.5 cm², stage D) who have favorable valve morphology in the absence of left atrial thrombus or moderate to severe MR (level of evidence: A). ^[6] ​

• Percutaneous mitral balloon valvotomy is effective for symptomatic patients (New York Heart Association [NYHA] functional class II, III, or IV) with moderate or severe MS and valve morphology favorable for percutaneous mitral balloon valvotomy in the absence of left atrial thrombus or moderate to severe MR) (level of evidence: A). ^[7]

• Mitral valve surgery (repair, commissurotomy, or valve replacement) is indicated in severely symptomatic patients (NYHA class III to IV) with severe MS (mitral valve area ≤1.5 cm², stage D) who are not high risk for surgery and who are not candidates for or who have failed previous percutaneous mitral balloon commissurotomy (level of evidence: B). ^[6]

• Percutaneous mitral balloon valvotomy is effective for asymptomatic patients with moderate or severe MS and valve morphology that is favorable for percutaneous mitral balloon valvotomy who have pulmonary hypertension (pulmonary artery systolic pressure > 50 mmHg at rest or > 60 mmHg with exercise) in the absence of left atrial thrombus or moderate to severe MR (level of evidence: C). ^[7]

• Concomitant mitral valve surgery is indicated for patients with severe MS (mitral valve area ≤1.5 cm², stage C or D) undergoing cardiac surgery for other indications (level of evidence: C). ^[6]

• Percutaneous mitral balloon commissurotomy is recommended before pregnancy for asymptomatic patients with severe MS (mitral valve area ≤1.5 cm², stage C) who have valve morphology favorable for percutaneous mitral balloon commissurotomy (level of evidence: C). ^[6]

Class IIa recommendations

• Percutaneous mitral balloon valvotomy is reasonable for patients with moderate or severe MS who have a nonpliable calcified valve, are in NYHA functional class III–IV, and either are not candidates for surgery or are at high risk with surgery (level of evidence: C). ^[7]

• Percutaneous mitral balloon commissurotomy is reasonable for asymptomatic patients with very severe MS (mitral valve area ≤1.0 cm², stage C) and favorable valve morphology in the absence of left atrial thrombus or moderate-to-severe MR (level of evidence: C). ^[6]

• Mitral valve surgery is reasonable for severely symptomatic patients (NYHA class III to IV) with severe MS (mitral valve area ≤1.5 cm², stage D), provided there are other operative indications (eg, aortic valve disease, coronary artery disease, tricuspid regurgitation, aortic aneurysm) (level of evidence: C). ^[6]

• Percutaneous mitral balloon commissurotomy is reasonable for pregnant patients with severe MS (mitral valve area ≤1.5 cm², stage D) with valve morphology favorable for percutaneous mitral balloon commissurotomy who remain symptomatic with NYHA class III to IV heart failure symptoms despite medical therapy (level of evidence: B). ^[6]

• Valve intervention is reasonable for pregnant patients with severe MS (mitral valve area ≤1.5 cm², stage D) and valve morphology not favorable for percutaneous mitral balloon commissurotomy only if there are refractory NYHA class IV heart failure symptoms (level of evidence: C). ^[6]

Class IIb recommendations

• Percutaneous mitral balloon commissurotomy may be considered for asymptomatic patients with severe MS (mitral valve area ≤1.5 cm², stage C) and valve morphology favorable for percutaneous mitral balloon commissurotomy who have new onset of atrial fibrillation in the absence of left atrial thrombus or moderate to severe MR (level of evidence: C). ^[6]

• Percutaneous mitral balloon commissurotomy may be considered for symptomatic patients with mitral valve area greater than 1.5 cm² if there is evidence of hemodynamically significant MS based on pulmonary artery wedge pressure greater than 25 mmHg or mean mitral valve gradient greater than 15 mmHg during exercise (level of evidence: C). ^[6]

• Percutaneous mitral balloon commissurotomy may be considered for severely symptomatic patients (NYHA functional class III-IV) with severe MS (mitral valve area ≤1.5 cm², stage D) who have suboptimal valve anatomy and who are not candidates for surgery or are at high risk for surgery (level of evidence: C). ^[6]

• Concomitant mitral valve surgery may be considered for patients with moderate MS (mitral valve area 1.6 cm² to 2.0 cm²) undergoing cardiac surgery for other indications (level of evidence: C). ^[6]

• Moderate-risk elective noncardiac surgery in patients with appropriate intraoperative and postoperative hemodynamic monitoring may be reasonable to perform in asymptomatic patients with severe MS if the valve morphology is not favorable for percutaneous balloon mitral commissurotomy (level of evidence: C). ^[6]

The images below depict simultaneous tracings of pulmonary capillary wedge pressure and left ventricular pressure in a patient with mitral stenosis before and after valvuloplasty.

European Society of Cardiology/European Association for Cardio-Thoracic Surgery (ESC/EACTS) guidelines

Indications for percutaneous mitral commissurotomy in clinically significant (moderate or severe) MS (valve area ≤1.5 cm²) ^[5]

• Symptomatic patients without unfavorable characteristics for percutaneous mitral commissurotomy (Class I, level evidence B)

• Any symptomatic patients with a contraindication or a high risk for surgery (Class I, level evidence C)

• Mitral valve surgery is indicated in symptomatic patients who are not suitable candidates for percutaneous mitral commissurotomy (Class I, level evidence C)

• Percutaneous mitral commissurotomy should be considered as the initial treatment in symptomatic patients with suboptimal anatomy but no unfavorable clinical characteristics for the procedure (Class IIa, level evidence C)

• Percutaneous mitral commissurotomy should be considered in asymptomatic patients without unfavorable clinical and anatomic characteristics for the procedure and (a) high thromboembolic risk (history of systemic embolism, dense spontaneous contrast in the left atrium, new onset or paroxysmal atrial fibrillation), and/or (b) high risk of hemodynamic decompensation (at-rest systolic pulmonary pressure >50 mmHg, need for major noncardiac surgery, desire for pregnancy) (Class IIa, level evidence C)

American College of Cardiology/American Heart Association (ACC/AHA) guidelines

Contraindications for percutaneous mitral balloon valvuloplasty (ie, class III recommendations) ^[7]

• Percutaneous mitral balloon valvotomy is not indicated for patients with mild mitral stenosis (MS) (level of evidence: C)

• Percutaneous mitral balloon valvotomy should not be performed in patients with moderate to severe mitral regurgitation (MR) or left atrial thrombus (level of evidence: C)

Transesophageal echocardiography is recommended before the procedure to determine the presence of left atrial thrombus, with specific attention paid to the left atrial appendage. If a thrombus is found, 3 months of anticoagulation with warfarin may result in resolution of the thrombus. A prognostic model for predicting the resolution of left atrial thrombi in candidates for percutaneous mitral commissurotomy has been suggested. ^[7]

European Society of Cardiology/European Association for Cardio-Thoracic Surgery (ESC/EACTS) guidelines

The ESC guidelines has the following contraindications for percutaneous mitral commissurotomy ^[5] :

• Mitral valve area larger than 1.5 cm ²; if symptoms cannot be explained by another cause and if the anatomy is favorable, then the procedure may be considered in those with a valve area above 1.5 cm ²
• Presence of a left atrial thrombus
• Presence of a more than mild mitral regurgitation
• Presence of severe or bi-comissural calcification
• Absence of commissural fusion
• Presence of severe concomitant aortic valve disease, or severe combined tricuspid stenosis and regurgitation requiring surgery
• Presence of concomitant coronary artery disease requiring bypass surgery

Preprocedural planning

The likelihood of hemodynamic benefit and the risk of complications with balloon valvuloplasty are predicted by the morphologic features of the valve leaflets and subvalvular structures. With rigid, thickened valves that exhibit extensive subvalvular fibrosis and calcification, results will be suboptimal. ^[7]

Physical examination is an important initial step in assessing the pliability of the valve. Accentuation of the first heart sound (S1) occurs when the mitral valve leaflets are flexible. Marked calcification or thickening of the mitral valve leaflets reduces the amplitude of S1, probably because of diminished motion of the leaflets.

The opening snap (OS) of the mitral valve is caused by a sudden tensing of the valve leaflets after the valve cusps have completed their opening excursion. It is most readily audible at the apex; if present, it indicates that the mitral valve has at least some mobility. ^[8]

The echocardiographic scoring system developed by Wilkins et al (see the table below) is useful for estimating likely outcomes of PMBV. ^[9]

Table 1. Echocardiographic Scoring System to Predict Outcome of Mitral Balloon Valvuloplasty (Open Table in a new window)

In this system, points are given for leaflet mobility, valve thickening, subvalvular thickening, and valvular calcification. The final score is determined by adding the points for each of the components (maximum, 16 points). A score of 8 or lower is usually associated with excellent immediate and long-term results for PMBV, whereas scores higher than 8 are associated with less impressive results, including the risk of development of MR.

The image below depicts mitral stenosis as demonstrated with two-dimensional (2D) echocardiography.

Another important factor in determining the suitability of the valve for PMBV is the presence of commissural calcification, assessed by means of a 2-D echocardiographic short-axis view. The presence or absence of severe calcification of one or both commissures is an independent determinant of near-term success during the procedure, as well as long-term outcome. ^{[7, 10]}

The emphasis on direct examination of the commissures may allow treatment to be extended to some patients with unfavorable scores (eg, patients with severe leaflet calcification and decreased mobility without severe calcification of the commissures).

Other patient subsets in whom results may not be accurately predicted by a simple score include elderly patients with nonrheumatic MS caused by annular calcification encroaching into the base of the mitral leaflet and patient with severe mitral inflow obstruction due to severe subvalvular fusion and little commissural fusion. Neither of these patient subsets should undergo PMBV.

PMBV is now the procedure of choice for selected MS patients. Optimally, a team comprising an interventionalist and a cardiac imager collaborates during the preprocedural and periprocedural assessment. ^[11] Targeted echocardiography not only is critical to the selection of candidates for PMBV but also can be of great value in guiding the procedure and assessing the results. ^[12] Simultaneous echocardiography (transthoracic, transesophageal, or intracardiac echocardiography) directly illustrates the relation of the catheter to myocardial structures.

In patients whose anatomy is distorted by an enlarged left atrium, echocardiography can be used to ensure that the catheter crosses the atrial septum at the level of the fossa ovalis. Catheter crossing elsewhere may give rise to complications, and a through the muscular portion of the septum may result in difficult manipulation of the balloon catheter. Echocardiography is useful for directing the catheter across the mitral valve; the balloon initially tends to position itself towards the lateral annulus in the left atrium.

Echocardiography can be used to avoid the complications that occur when a catheter is placed directly into the subvalvular apparatus and to confirm that the balloon is properly seated across the mitral valve. Finally, hemodynamic evaluation of the transmitral gradient and the severity of MR is easily performed by means of Doppler echocardiography—more accurately than by means of catheterization hemodynamic studies. ^[12]

Patient preparation

The equipment required depends on the specific approach to the procedure (see Technique). Usually, PMBV is done with the patient under moderate sedation. The patient remains in the supine position during the procedure.

Approach considerations

Retrograde (transarterial) and antegrade (transvenous) approaches to percutaneous mitral balloon valvuloplasty (PMBV) have been described. The retrograde approach eliminates the risk of atrial septal defect but carries a risk of potential arterial damage; because of its complexity, it has now been largely abandoned. ^[13] Currently, the antegrade approach with transseptal catheterization is more widely used. It is usually performed through the femoral vein; however, the jugular venous approach has also been described. ^[14]

Choice of technique

The Inoue balloon technique, first described in 1984, ^[1] is the one most commonly employed today (and the one used by the authors). Alternatives exist (see below) but are not as popular.

Double-balloon technique

The double-balloon technique is one of the 2 main techniques that are currently used. In this approach, after transseptal catheterization, a balloon-tipped catheter is advanced into the left ventricle. One or two exchange guide wires are advanced through the lumen of the balloon-tipped catheter and positioned in the apex of the left ventricle or, less frequently, in the ascending aorta.

The balloon-tipped catheter is withdrawn over the guide wires, and the interatrial septum is dilated with the use of a peripheral angioplasty balloon (6-8 mm in diameter). Finally, the valvotomy balloons (15-20 mm in diameter) are advanced over the guide wires and positioned across the mitral valve. ^[13]

Multitrack technique

Bonhoeffer et al have described the use of the multitrack system, which is a refinement of the double-balloon technique that employs a monorail system requiring only 1 guide wire. ^[15] This technique allows easier dilation than the standard technique; however, clinical experience with the multitrack system is still limited.

Metallic commissurotomy

Cribier et al introduced the metallic commissurotomy during the 1990s. ^[16] This procedure is as efficacious as balloon commissurotomy, but it is more demanding on the operator than the Inoue technique and appears to carry a higher risk of hemopericardium as a consequence of the presence of a stiff guide wire in the left ventricle. The dilator is reusable, and the potential advantage of the procedure is its cost-effectiveness.

Inoue balloon technique

The main steps of the Inoue approach to PMBV, as performed by the authors, are as follows.

Vascular access

A 7-French sheath is inserted in the right femoral vein for transseptal access; another is inserted in the left femoral vein (or a second venous sheath in the right femoral vein, depending on physician preference) for a pulmonary artery catheter. A 5-French sheath is placed in the left femoral artery for left-heart catheterization. Three pressure transducers are required for simultaneous left atrial, left ventricular, and right-side pressures. A pigtail (or multipurpose) catheter is advanced to the aortic valve, and aortic pressures are obtained.

Note that because a time delay is associated with transmission of the left atrial pressure through the pulmonary vasculature to the pulmonary capillary wedge position, using the pulmonary capillary wedge pressure instead of the left atrial pressure tends to result in overestimation of the gradient across the mitral valve.

Transseptal catheterization

The goal of transseptal catheterization is to cross from the right atrium to the left atrium through the fossa ovalis. Puncture of the fossa ovalis itself is safe; the danger of the transseptal approach lies in the possibility that the needle and catheter will puncture an adjacent structure (eg, the coronary sinus, the posterior wall of the right atrium, or the aortic root). To minimize the risk of complications, the operator must have a detailed knowledge of the regional anatomy of the atrial septum.

As viewed from the feet with the patient lying supine, the plane of the atrial septum runs from 1 o’clock to 7 o’clock. The fossa ovalis is posterior and caudal to the aortic root, anterior to the free wall of the right atrium, superior and posteriorly to the ostium of the coronary sinus, and well posterior of the tricuspid annulus and the right atrial appendage. It is approximately 2 cm in diameter and is bounded superiorly by the limbus.

In the presence of aortic or mitral valve pathology, the atrial septal anatomy can be distorted. In mitral stenosis (MS), the intra-atrial septum becomes flatter with a more horizontal orientation, and the fossa tends to lie lower.

In the classic approach, transseptal catheterization is performed from the right femoral vein. A 70-cm curved Brockenbrough needle that tapers from 18 gauge to 21 gauge at the tip is used. The needle is introduced via a matching Brockenbrough catheter or an 8-French Mullins sheath-dilator combination. Biplanar imaging is used. The current Mullins sheath designs have a side-arm connection and a back-bleed valve, allowing ongoing measurement of left atrial pressure. ^{[13, 17]}

The hub of the Mullins introducer to the Mullins sheath is locked. The sheath is inserted over a flexible 0.032- or 0.035-in. 145-cm J-tip guide wire, then advanced to the low superior vena cava (SVC). Once the wire has been removed, the catheter is flushed.

The Brockenbrough needle is then advanced through the Mullins sheath and dilator until its tip is near, but not at, the distal aspect of the sheath. During this process, the needle and its direction indicator should be allowed to rotate freely so that the needle may follow the curves of the catheter and venous structures: the hub of the needle should never be grasped and rotated at this point. The progress of the needle tip should be monitored fluoroscopically to look for any sign of perforation of the catheter by the needle.

The stylet is removed at the diaphragm, and the needle hub is connected to a pressure manifold via a stopcock with a short length of tubing and carefully flushed. The SVC pressure is then recorded through the needle, with the needle rotated so that the direction indicator points anteriorly.

Under the guidance of continuous biplane fluoroscopy with straight posteroanterior and lateral views and with a pigtail catheter in the ascending aorta for pressure monitoring and spatial orientation of the aorta, the Brockenbrough needle and catheter are held in a constant relation as they are withdrawn slowly with both hands. The direction indicator is firmly controlled with the right hand and used to rotate the needle clockwise during withdrawal from the SVC until the arrow is oriented posteromedially (4 o’clock position as seen from below).

As the tip of the catheter enters the right atrium, it moves slightly rightward (to the patient’s left). With slow withdrawal of the needle and catheter in the 4 o’clock orientation, a second rightward movement is felt as the catheter tip slips over the bulge of the ascending aorta. With further slow withdrawal, a third rightward movement is felt as the catheter tip snaps into the fossa ovalis.

If the foramen is patent, the catheter may cross into the left atrium spontaneously at this point, as indicated by a change in atrial pressure waveform and the ability to withdraw oxygenated blood from the needle. Otherwise, the needle is advanced to the tip of the catheter, and the whole system is then advanced. The first “pop” is due to advancing the needle and dilator; once this occurs, the system is fixed in position and advanced until a second “pop” is felt. The sheath is slightly advanced, and the needle and dilator are removed.

Successful entry into the left atrium should be confirmed both by recording a left atrial pressure waveform and by withdrawing oxygenated blood or demonstrating the typical fluoroscopic appearance of the left atrium during a small contrast injection through the needle. Once the catheter is safely in the left atrium, heparin (usually 5000 U) is administered for anticoagulation.

Role of radiofrequency needles for transseptal catheterization

Radiofrequency (RF) needles have become more popular for transseptal puncture in structural heart interventions to reduce procedure time, as well as to improve success rates and spatial accuracy. RF needles allow the physician to advance across the septum in a precise manner without using excessive force. Also, because the needle tip is not sharp, it does not scrape off plastic particles from the inside of the delivery catheter as it is being advanced.

The use of RF needles is particularly beneficial for patients who have had prior procedures, which often result in a thickened or scarred septa, and it also adds a level of control to the operator when treating patients with aneurysmal or elastic septa that is challenging to cross with a standard needle. In a study published by Sharma et al, procedural unassisted crossing success was higher with the RF needle approach as compared to the standard needle approach. ^[18] Procedural times and degree of septum tenting favored the RF needle approach over that of the standard needle. RF needle was a successful strategy when standard needle failed. Accuracy was similar with both approaches. There were no major complications with either approach. ^[18]

Role of echocardiographic guidance in transseptal catheterization

Although echocardiography is not required during transseptal catheterization, this imaging modality could potentially improve the safety and precision of the procedure, especially in the early phase of the operator's experience. ^{[19, 20, 21]} These becomes particularly important in patients with previous septal surgeries or punctures, an excessively mobile septum, or with very large atria or distorted anatomy, as can be seen in patients with significant scoliosis or a history of pneumonectomy.

Both transesophageal (TEE) and intracardiac echocardiographic (ICE) approaches have been used ^{[19, 20, 21]} ; however, using the TEE approach is not always easy in the cardiac catheterization laboratory (it requires extra physician support and, often, general anesthesia), and it is best used in selected cases with severe anatomic distortions or other technical challenges. More recently, a real-time three-dimensional (3-D) TEE technique has been used to enhance the visualization of the interatrial septum and the assessment of optimal location for transpetal puncture.

Currently, ICE has become the imaging modality of choice for many operators to identify the fossa ovalis and to guide placement of transseptal puncture at the limbus. ^{[19, 20, 21]} Tenting of the septum by the transseptal needle can be visualized by echocardiography, and the exact position of the septal puncture can be chosen. Crossing at the level of the fossa ovalis in the posterior inferior part is best for most PMBVs. Additionally, a full survey by ICE prior to performing PMBV to assess the left atrial appendage and the mitral valve can be done.

Echocardiography is also very helpful to optimize balloon position across the mitral valve leaflets and to avoid entrapment in the subvalvular apparatus. The ICE catheters provide real-time 360-degree images of the structures surrounding the catheter tip, and they are capable of producing high frequencies in the 10-30 MHz range, resulting in adequate imaging for up to 10 cm from the transducer, with excellent spatial resolution. The present generation of ICE probes range from 8 to 10 French in diameter. ^{[19, 20, 21]}

Hemodynamic assessment

The pulmonary artery catheter is then advanced through the left femoral venous sheath (or second right femoral sheath), and thermodilution cardiac output is measured. The pigtail catheter is advanced to the left ventricle to measure ventricular pressure. The gradient across the mitral valve is measured, and the valve area evaluated. Echocardiography can also be used to measure the gradient across the mitral valve, and parasternal short-axis views are used to look at mitral valve commissures.

Insertion of Inoue balloon

The Inoue balloon is composed of a nylon and rubber micromesh and is both self-positioning and pressure-extensible. It is available in 4 sizes: 24, 26, 28, and 30 mm. The balloon size is chosen in accordance with the patient’s height (26 mm in very small patients or infants, 28 mm in patients shorter than 1.6 m, and 30 mm in patients taller than 1.6 m); alternatively, the following equation may be used as a rule of thumb:

Balloon size = Patient height (cm)/10 + 10

The silver metal hub is advanced to the gold metal hub (the gold hub should not be advanced to the plastic hub without a balloon over the Inoue wire, because the gold metal elongator will perforate the balloon).

The vent port is opened and flushed with saline through the balloon port; this should be done slowly so as not to inflate the balloon. Once the vent port is properly flushed, it is closed. This process ensures that the balloon will be completely free of air should it rupture.

The balloon is then inflated to the desired size, with every 1 mL in the syringe equaling a 1-mm increase in the diameter of the balloon (the balloon size is measured at the waist). The balloon diameter is measured outside the patient’s body with the ruler included in the kit.

Inoue wire is advanced to the left atrium, making loops in the atrium, and the Mullins sheath is removed. The interatrial septum is dilated with a 14-French dilator. The Inoue balloon is loaded on the wire (this part of the procedure is sheathless), and the balloon is elongated outside the body by advancing the gold hub (with the silver hub attached) to the plastic hub and securing it (if this step is not done over a wire, the gold metal elongator will perforate the balloon).

The Inoue balloon is then advanced to the left atrium, and the guide wire and inner metal elongator are removed. The silver and gold elongators are pulled back in a single motion to the point where the gold elongator stops (approximately 3 cm), and the silver hub and the Inoue wire are pulled back and all the way out. The stylet is then inserted; this creates a more receptive balloon for tuning. The left ventricular catheter is pulled out of the ventricle to the ascending aorta.

The Inoue balloon is maneuvered under echocardiographic or fluoroscopic guidance. The stylet is pulled out, and the balloon is advanced to the left ventricle across the mitral valve by means of a counterclockwise rotation. (This maneuver moves the balloon anteriorly and straightens the balloon; the stylet is J-shaped.)

The distal portion of the Inoue balloon is inflated, and the balloon is pulled back to ensure stabilization beneath the mitral valve annulus. Inflation occurs next at the level of the proximal part of the balloon and finally in the central portion, with the disappearance of the central waist at full inflation. The video below depicts this technique as performed by authors at a different institution.

The balloon is then deflated and withdrawn into the left atrium. Depending on the Abascal score and the presence or absence of commissural calcification, the first inflation may be stopped short of the maximal balloon size, then increased in 1-mm steps, depending on results.

Echocardiographic measurements are repeated. At this point, the pulmonary arterial pressure should be monitored closely because a jump in this pressure suggests the development of acute mitral regurgitation (MR). If, on color Doppler echocardiography, MR has not increased by more than 1 grade and the mitral valve area is less than 1 cm²/m² of body surface area, the balloon is advanced across the valve, and mitral valvuloplasty is repeated with a balloon diameter increased by 1 mm.

While the balloon is withdrawn into the left atrium, the stylet is removed and the catheter is connected to pressure monitoring. This should be done through the middle port, the one that the Inoue wire goes through. At this point, the pigtail (or multipurpose) catheter is readvanced into the left ventricle, and hemodynamic measurements (including cardiac output) are repeated.

The Inoue balloon is then reelongated in the left atrium by inserting the Inoue wire telescoped through the silver metal elongator to the gold hub. The operator should make sure all of the loops are in the left atrium before reattaching the gold hub to the plastic hub.

Before pulling out the pulmonary artery catheter out, the operator should check oxygen saturations in the pulmonary artery, the inferior vena cava (IVC), and the SVC to check for any new left-to-right shunts.

Completion and evaluation of results

The procedure may be ended when there is an adequate increase in valve area, decrease in the mitral valve gradient, or increase in the degree of MR.

Evaluation of immediate results is mainly determined on the basis of hemodynamic criteria. The 2 definitions frequently used for good immediate results are as follows:

• A final valve area larger than 1.5 cm² without mitral regurgitation greater than 2+

• A final valve area larger than 1.5 cm² and an increase in valve area of at least 25%

Prediction of the results is multifactorial. In addition to morphologic factors, preoperative variables (eg, age, functional class, history of surgical commissurotomy, small mitral valve area, presence of mitral regurgitation before the procedure, sinus rhythm, pulmonary artery pressure, and severity of tricuspid regurgitation) and procedural factors (eg, balloon size) can be independent predictors of immediate outcome. ^{[13, 17, 22, 23]}

The image below depicts tricuspid regurgitation after percutaneous mitral valvuloplasty.

Complications of the procedure

Procedural mortality ranges from 0-3% in most series. The main causes of mortality include left ventricular perforation and the patient’s poor general condition.

The frequency of severe MR ranges from 2% to 19% in different series. ^{[22, 24, 25]} Surgical findings ^[26] suggest that this complication is related to noncommissural tearing of the posterior or anterior leaflet. Additionally, with significant asymmetric commissural calcification, the noncalcified commissure can tear, causing severe MR.

The frequency of atrial septal defects after mitral valvuloplasty ranges from 10% to 90% in different series. These are typically small and restrictive shunts. Significant right-to-left shunts occur on rare occasions in patients who had pulmonary hypertension and elevated right heart pressures.

The reported incidence of hemopericardium ranges from 0.5% to 12.0%. This complication may be due to transseptal catheterization or to apex perforation by the guide wires or the balloon. In case of pericardial hemorrhage, emergency pericardiocentesis should be performed in the catheterization laboratory to stabilize the patient’s condition and allow transfer for cardiac surgery.

The frequency of embolic events related to mitral valvuloplasty ranges from 0.5% to 5.0%. On rare occasions, such events can cause of permanent severe disability and even death. In view of the severe potential consequences of this complication, it is critical for the operators to take all possible precautions to prevent it.

The incidence of complete heart block is 1.5%. This is mostly transient; rarely, patients may require a permanent pacemaker.

The failure rate ranges from 1% to 17%. Failures can result from unfavorable anatomy (eg, severe atrial enlargement or predominant subvalvular stenosis or heavy calcification), but most failures occur during the initial portion of the operator's learning curve, often as a consequence of an unsuccessful transseptal puncture or inability to position the balloon across the mitral valve correctly.

Restenosis after percutaneous mitral valvuloplasty is generally defined as a loss of more than 50% of the initial gain with a valve area less than 1.5 cm². The incidence of restenosis after a successful procedure ranges from 2% to 40% in different studies, at time intervals ranging from 3 to 10 years. Depending on the anatomy, restenosis can be treated either with repeat PMBV or with surgical mitral valve replacement. ^{[13, 22, 24, 27, 28, 29, 30]}