Surgical and investigational approaches to management of mitral stenosis

INTRODUCTION — Mitral stenosis (MS) is a condition caused most commonly by rheumatic heart disease and characterized by obstruction of blood flow across the mitral valve (MV) from the left atrium to the left ventricle. The mechanical obstruction leads to increases in pressure within the left atrium, pulmonary vasculature, and right side of the heart. Progressive MS leads to complications including heart failure, systemic arterial embolism, hemoptysis, pulmonary hypertension, and death. Medical therapy can alleviate symptoms, but surgical or percutaneous intervention is required to relieve the obstruction to flow. (See "Rheumatic mitral stenosis: Clinical manifestations and diagnosis" and "Rheumatic mitral stenosis: Overview of management".)

Surgical and investigational approaches to management of MS are reviewed here. Issues directly related to the indications for intervention and choice of percutaneous mitral balloon valvotomy versus surgery and the medical management of MS are discussed separately. (See "Percutaneous mitral balloon commissurotomy in adults" and "Rheumatic mitral stenosis: Overview of management".)

PREPROCEDURE ASSESSMENT

Assessment of valve pathology — Preprocedural imaging of the mitral valve (MV) includes echocardiography as well as multidetector computed tomography (MDCT), when available. Echocardiography (initial transthoracic, complemented by transesophageal if needed) is used primarily for the hemodynamic (functional) assessment of valve pathology while MDCT is essential for precise preoperative anatomical delineation of MV apparatus anatomy and pathology including delineation of whether calcium is limited to the leaflet, involves the subvalvular apparatus, or even extends into the left ventricle beyond the mitral annulus.

Transthoracic echocardiography is the initial test of choice for assessment of MV pathology and hemodynamic (functional) severity of disease. In selected cases in which transthoracic echocardiographic assessment is incomplete, transesophageal echocardiography is useful for further characterization of pathology including the presence/extent of calcification and assessment of mitral regurgitation. When available, MDCT is used for precise anatomical delineation of abnormalities/pathology of the MV apparatus.

The feasibility of percutaneous or surgical commissurotomy is assessed based upon the type and severity of pathologic change involving the valve and subvalvular apparatus. For percutaneous commissurotomy, this is most commonly assessed using the Wilkins score, as discussed separately. Assessment for open MV surgery includes more extensive evaluation of all rheumatic pathology including the leaflets (to determine need for surgical delamination and augmentation with pericardium), commissures, and subchordal/chordal (elongation, splitting, chordal transfer or insertion) and papillary muscle pathologies. (See "Percutaneous mitral balloon commissurotomy in adults" and "Percutaneous mitral balloon commissurotomy in adults", section on 'Evaluation of candidates for PMBC'.)

Most cases of MS are caused by rheumatic heart disease with mitral commissural adhesion, thickened immobile MV leaflets, fibrosis, thickening, shortening, fusion, and calcification of the chordae tendineae. Infrequent causes of MS include mitral annular calcification (MAC) and congenital MS (including parachute MV). The differing features of these causes enable differentiation by echocardiography. (See "Pathophysiology and natural history of mitral stenosis", section on 'Etiology'.)

For patients suspected of having significant MAC, cardiac CT imaging provides the most accurate delineation of the severity and location of annular and extra-annular calcification.

Risk assessment — Patients who are candidates for MV intervention for MS should be evaluated and discussed by a heart valve team to assess the potential risks and benefits of various options for MV intervention. Methods for estimating the mortality risk of valve surgery are discussed separately. (See "Estimating the risk of valvular procedures".)

Preoperative coronary angiography — We recommend a similar approach to the American College of Cardiology/American Heart Association 2020 guidelines on the management of patients with valvular heart disease regarding the use of cardiac catheterization and coronary angiography to establish the presence of coronary artery disease [1].

There were two main indications for coronary angiography prior to MV surgery:

●Patients with angina, objective evidence of ischemia, decreased left ventricular systolic function, or a history of coronary disease.

●In patients at risk for coronary disease, including men >40 years old and postmenopausal women with high pretest likelihood of cardiovascular disease.

MDCT is used as an alternative to invasive coronary angiography in patients at risk for coronary disease (including men >40 years old and postmenopausal women) with low to intermediate pretest likelihood of cardiovascular disease [1]. An approach to cardiovascular risk assessment is discussed separately. (See "Atherosclerotic cardiovascular disease risk assessment for primary prevention in adults: Our approach".)

For high-risk patients being considered for transcatheter MV replacement (see 'Transcatheter mitral valve replacement' below), preoperative coronary angiography is recommended. By contrast, coronary angiography is not required solely for coronary risk factors in patients undergoing percutaneous mitral balloon valvotomy (PMBV).

CHOICE OF PROCEDURE — For patients with MS with an indication for intervention, the choice among mitral valve (MV) procedures (percutaneous versus surgical approaches) is based largely upon valve pathology, estimated procedural risks, and is also impacted by local expertise and availability of interventional and surgical procedures. The American College of Cardiology/American Heart Association (ACC/AHA) guidelines emphasize the importance of these procedures being performed at a comprehensive valve center due to the expertise, experience, and resources required to optimally treat MS patients [1]. As shown in the prospective REMEDY study of the global characteristics of rheumatic valvular disease, there is a gradient of availability of interventional procedures among the low, middle income, or upper middle income countries [2,3].

Rheumatic MS — When intervention is warranted in patients with rheumatic MS with valve morphology favorable for percutaneous mitral balloon valvotomy (PMBV; ie, limited calcium and valve thickening, pliable leaflets, and limited subvalvular thickening), no left atrial thrombus, and without moderate to severe (3+ to 4+) mitral regurgitation, we recommend PMBV, as recommended in the ACC/AHA guidelines [1]. The data supporting this conclusion are presented separately. (See "Percutaneous mitral balloon commissurotomy in adults".)

However, even with unfavorable anatomy, PMBV may be performed at a comprehensive valve center as a palliative procedure if the patient is deemed to be at high risk for morbidity and mortality with surgery and there is no left atrial thrombus or moderate to severe mitral regurgitation. (See "Percutaneous mitral balloon commissurotomy in adults", section on 'Use'.)

The following clinical features favor MV surgery (open commissurotomy and repair or valve replacement) as the preferred procedure for MS [4]:

●Suboptimal valve anatomy for PMBV, such as severe valve leaflet thickening/calcification/immobility with subvalvular fibrosis.

●Left atrial thrombus that persists despite anticoagulation.

●Concomitant moderate to severe mitral regurgitation.

●Concomitant severe tricuspid regurgitation. (See 'Tricuspid valve repair' below.)

Among patients with unfavorable valve morphology who are referred for MV surgery, valve repair is performed if possible. The repair may include both open commissurotomy and placement of an annuloplasty ring after direct visualization of the valve [4]. (See 'Open commissurotomy and valve repair' below.)

MV replacement is generally considered the last alternative for the treatment of MS because of its higher perioperative mortality and potential for morbidity. However, in symptomatic patients with severe MS in whom neither PMBV nor surgical valve repair is possible, valve replacement results in marked symptomatic improvement and is associated with improved long-term survival. (See 'Outcomes' below.)

Mitral annular calcification — The ACC/AHA guidelines recommend that in severely symptomatic patients with severe MS (mitral valve area 1.5 cm² or less, stage D) attributable to extensive mitral annular calcification (MAC), valve intervention may be considered only after discussion of the high procedural risk and the individual patient’s preferences and values [1]. The prevalence of MAC increases with age, but severe MAC infrequently causes symptomatic calcific MS. Predisposing conditions for MAC include chronic kidney disease, prior chest irradiation, hypertension, and other conditions predisposing to left ventricular hypertrophy [5]. In patients with MS caused by MAC, PMBV (which treats commissural fusion in patients with rheumatic valve disease) is not effective. However, the presence of severe MAC complicates MV surgery and is associated with high operative mortality rates (see "Management and prognosis of mitral annular calcification", section on 'Mitral valve surgery').

Congenital MS — Surgery is usually preferred in patients with congenital MS, since the anatomy is complex, the utility of PMBV may be limited, and catheterization procedures are potentially dangerous. (See "Percutaneous mitral balloon commissurotomy in adults", section on 'Selective use for congenital MS'.)

MITRAL VALVE INTERVENTIONS

Mitral valve commissurotomy — Mitral valve (MV) commissurotomy for rheumatic MS can be performed by percutaneous, open surgical, or closed surgical procedures.

Percutaneous mitral balloon valvotomy — In individuals with MS with characteristics favorable for percutaneous mitral balloon valvotomy (PMBV or percutaneous mitral balloon commissurotomy), the safety and efficacy of PMBV compared with surgical commissurotomy (open or closed) have been established by randomized controlled trials, as discussed separately. (See "Percutaneous mitral balloon commissurotomy in adults".)

Open commissurotomy and valve repair — Open surgical commissurotomy performed with the aid of cardiopulmonary bypass is generally preferred to closed commissurotomy but is used only in selected cases in health care settings in which PMBV is available. (See 'Rheumatic MS' above.)

Open commissurotomy is performed via a median sternotomy and has the advantage of allowing the surgeon to inspect the MV and subvalvular apparatus. In addition to splitting the commissures under direct vision, the valve can be repaired by debriding calcium deposits and abnormal cusp tissue followed by replacement with autologous pericardium and artificial chordae, dividing fused chordae tendineae, and splitting papillary muscles when appropriate. When mitral regurgitation is present, an annuloplasty ring is placed to restore valve competency.

Use — PMBV is generally preferred to open commissurotomy since outcomes with PMBV were similar or better than those with open commissurotomy in clinical trials [6,7]. Other advantages of PMBV are shorter hospital stay, avoidance of the morbidity of thoracotomy, and a better outcome if repeat intervention is required [8] (see "Percutaneous mitral balloon commissurotomy in adults" and 'Repeat commissurotomy' below). However, open commissurotomy with valve repair remains an appropriate choice in patients who are not candidates for PMBV due to valve deformity or calcification, left atrial thrombus, or significant mitral regurgitation. Similar to closed commissurotomy and balloon valvotomy, the success of the procedure depends upon a favorable valve morphology (see 'Choice of procedure' above). In addition, thrombectomy can be performed to remove a left atrial thrombus, and many surgeons amputate or ligate the left atrial appendage to remove a potential source of embolism. (See 'Left atrial appendage ligation' below.)

Outcome — The safety and efficacy of open commissurotomy are well established. Successful commissurotomy is generally defined as MV area >1.5 cm² (normal 4 to 6 cm²) and a decrease in left atrial pressure to ≤18 mmHg in the absence of complications; the most common complication is mitral regurgitation, which occurs in 2 to 10 percent of patients.

Results from several studies have shown no residual stenosis with open commissurotomy; perioperative mortality rates are less than 1 percent and, at five to seven years, only 7 percent of patients need a reintervention [6,7,9]. The absence of residual stenosis means the acute success rate is essentially 100 percent in candidates with suitable valve morphology. Observational data show lower cardiac mortality rates with mitral repair compared with MV replacement, although cardiac mortality rates are similar after adjustment for baseline differences [10]. (See "Echocardiographic evaluation of the mitral valve".)

Closed surgical commissurotomy — The earliest surgical procedures for the treatment of MS were variations of closed commissurotomy [11]. This operation is performed on a beating heart, which is generally exposed via a left thoracotomy incision. The surgeon then uses either a transatrial or transventricular approach to introduce a dilator across the MV [12]. An obvious limitation compared with other surgical approaches is the inability to directly visualize the MV.

Use — Closed commissurotomy is associated with worse long-term outcomes compared with PMBV and open commissurotomy [6,13] and thus is not recommended in settings in which PMBV or open MV surgery is available. It is still performed in some developing nations where cost and lack of balloon valvotomy capability are continuing problems.

Closed commissurotomy has also been performed successfully in pregnant women in whom correction of MS is indicated [14], but PMBV is preferred. (See "Pregnancy in women with mitral stenosis", section on 'Clinical management'.)

Outcomes — Success of closed commissurotomy depends upon a favorable valve morphology. As a result, only patients with pliable MV leaflets, minimal calcification, and lack of significant subvalvular involvement historically were candidates for this procedure. Absolute contraindications included the presence of an atrial thrombus or moderate to severe mitral regurgitation, which can worsen upon commissural splitting.

The safety, efficacy, and long-term results of closed commissurotomy were determined in a report from India of 3724 consecutive patients, almost one-half of whom were New York Heart Association (NYHA) class IV at entry [15]. The following results were noted:

●The in-hospital mortality was 1.5 percent, and severe mitral regurgitation requiring immediate valve replacement developed in 0.3 percent.

●Mitral restenosis was noted after the fifth year of follow-up and varied from 4.2 to 11.4 per 1000 patients per year between the fifth and fifteenth year after surgery.

●Actuarial survival was 84 percent at 24 years; in addition, 86 percent of survivors at 15 years continued to have symptomatic improvement.

Repeat commissurotomy — PMBV and surgical commissurotomy can be repeated as long as the valve morphology remains favorable. The approximate frequency of repeat intervention is 7 to 10 percent at seven years with both procedures [6]. The outcome after repeat intervention may be less favorable than with the initial procedure because there is usually more valve deformity, calcification, and fibrosis.

Repeat PMBV carries no greater risk than the initial procedure; by contrast, repeat surgical commissurotomy has a mortality rate 2 to 10 times higher than that associated with the first operation [8]. Thus, despite the equivalent success with open surgical commissurotomy and PMBV [6], these concerns provide additional support for PMBV being the intervention of choice whenever technically feasible. Furthermore, PMBV can be performed for restenosis after initial surgical commissurotomy [16]. Surgical MV repair can often be successfully performed after prior PMBV [17]. (See "Percutaneous mitral balloon commissurotomy in adults" and "Percutaneous mitral balloon commissurotomy in adults", section on 'Repeat PMBC'.)

Mitral valve replacement — Surgical MV replacement is performed via a median sternotomy with exposure of the MV either via a left atrial incision or through the right atrium via a transseptal incision. The native leaflets are resected, followed by debridement of annular and subvalvular calcification. When necessary, annular reconstruction can be accomplished using an autologous or bovine pericardial patch, or resected anterior leaflet [18]. After debridement, a prosthetic valve is selected based on annular dimensions and sutured into the surrounding tissue.

Use — We recommend MV replacement for patients with moderate to severe MS (MV area ≤1.5 cm²) who have NYHA class III or IV symptoms, are not at high risk for surgery, and have an MV not amenable to either PMBV or open commissurotomy/repair (table 1 and figure 1) [4].

For patients with severe mitral annular calcification (MAC), PMBV is not an effective option, and surgical risk is often prohibitive; transcatheter MV replacement may be feasible. (See 'Transcatheter mitral valve replacement' below.)

Choice of valve — The choice between a bioprosthetic and mechanical mitral prosthetic valve requires consideration of multiple patient factors including age, life expectancy, likelihood of future pregnancy, bleeding risk, and presence of other indications for anticoagulation. The majority of patients with rheumatic MS are women of reproductive age [2]. Thus, the choice of a mechanical valve often entails coping with the risks of warfarin and other anticoagulants during pregnancy, as discussed in detail separately (see "Management of antithrombotic therapy for a prosthetic heart valve during pregnancy"). Thus, for women who are expected to have a future pregnancy, the benefit of avoiding the risks of anticoagulation for a mechanical valve is weighed against the risk of reoperation if a bioprosthetic valve is placed [19]. (See "Pregnancy and valve disease", section on 'Interventions prior to pregnancy'.)

For patients with MS who require valve replacement and are not expected to have future pregnancies (men and selected women), a mechanical prosthesis is commonly chosen because the patients are usually relatively young (<65 to 70 years old), and most require chronic anticoagulation for atrial fibrillation (the lack of requirement for anticoagulation being a relative advantage of bioprosthetic valves). Choice of MV prosthesis is discussed further separately. (See "Choice of prosthetic heart valve for surgical aortic or mitral valve replacement".)

Outcomes — MV replacement carries a higher perioperative mortality than the other approaches to correct MS. The perioperative mortality varies with the patient population, ranging from less than 5 percent in young healthy individuals to approximately 10 to 20 percent in older patients with significant comorbidities and pulmonary hypertension to 25 percent in patients with NYHA class IV (table 1) [4,20].

The last observation indicates the risk of delaying surgery. On the other hand, early MV replacement exposes the patient to a longer period of the persistent risks of valve thrombosis, systemic embolism, endocarditis, and bleeding secondary to chronic anticoagulant therapy. The risk of one of these complications is estimated to be 4 to 7 percent per year [21]. (See "Mechanical prosthetic valve thrombosis or obstruction: Clinical manifestations and diagnosis".)

In patients with severe MAC and associated MS, debridement of annular calcification carries considerable risk of atrioventricular groove disruption and is associated with prolonged cardiopulmonary bypass and aortic cross clamp times, contributing to high morbidity and mortality rates associated with this procedure, as discussed separately. (See "Management and prognosis of mitral annular calcification", section on 'Mitral valve surgery'.)

Prosthetic valve-patient mismatch — Observational studies have found an association between severe mitral prosthetic valve-patients mismatch (PPM) and increased mortality rate, although a causal relationship has not been established. Accordingly, to reduce the risk of PPM, surgeons implant the largest possible valve prosthesis. If the valve annulus is small, a mechanical prosthesis is favored when appropriate given its higher effective orifice area, lower transvalvular gradients, and lower risk of strut-related left ventricular outflow obstruction compared with a bioprosthesis.

Some degree of PPM is common among patients undergoing MV replacement. The effective orifice area (EOA) in prosthetic valves used for MV replacement is often small in relation to body size and may be associated with transvalvular pressure gradients similar to those in mild to moderate MS.

The possible detrimental impact of PPM on long-term survival was evaluated in a retrospective study of 929 patients undergoing MV replacement for both regurgitation and stenosis; the patients were followed for a mean of 6.3 years [22]. The indexed EOA was calculated for each patient and used to define PPM as severe when ≤0.9 cm²/m² (9 percent), moderate when >0.9 and ≤1.2 cm²/m² (69 percent), and nonsignificant when >1.2 cm²/m² (22 percent). Patients with severe PPM had 6- and 12-year survival that was significantly less than patients with moderate or nonsignificant PPM (74 versus 84 and 90 percent at six years, and 63 versus 76 and 82 percent at 12 years). On multivariate analysis, severe PPM was associated with a higher mortality (hazard ratio 3.2, 95% CI 1.5-6.8).

Concurrent surgical procedures — Patients undergoing open mitral commissurotomy or MV replacement commonly undergo concurrent procedures such as left atrial appendage ligation (aimed at reducing the risk of thromboembolism) and surgical procedures to prevent recurrent atrial fibrillation.

Left atrial appendage ligation — Exclusion of the left atrial appendage at the time of MV surgery (eg, open commissurotomy or MV replacement) is commonly performed, as discussed separately. (See "Atrial fibrillation: Left atrial appendage occlusion".)

Management of atrial fibrillation — Management of atrial fibrillation, including surgical approaches to prevent recurrent atrial fibrillation, is discussed separately. (See "Atrial fibrillation: Overview and management of new-onset atrial fibrillation" and "Atrial fibrillation: Surgical ablation".)

Tricuspid valve repair — Improvement in associated tricuspid regurgitation (TR) occurs in some but not all patients following successful PMBV. Based upon limited evidence, for patients with severe MS and severe TR, MV surgery combined with tricuspid valve (TV) repair is favored over PMBV.

A retrospective study in patients with severe MS and severe TR suggested that MV replacement combined with TV repair may produce better outcomes in patients with severe MS and severe TR than PMBV [23]. A retrospective study of patients with severe MS and severe TR compared outcomes in 48 patients undergoing PMBV versus 44 patients undergoing MV replacement combined with TV repair [23]. During 57 months of follow-up, two deaths occurred in each group, and there were seven cases of heart failure requiring surgical intervention in the PMBV group only (event rate difference was borderline significant, p = 0.05). Severe TR was improved to mild or absent TR in 98 percent of the surgery group and in 46 percent of the PMBV group.

Investigational approaches

Mitral valve bypass — Left atrial to left ventricular conduit (MV bypass) is an experimental surgical treatment for MS that has only been applied in a small number of patients at a few centers worldwide but may be safer than standard MV replacement in patients with severe MAC. Long-term outcomes of this technique are lacking, and potential risks of conduit-related complications including thrombosis and degeneration require study.

MV bypass was first reported in patients with congenital MS [24,25]. This technique has been applied to patients with MS due to severe MAC who are at high risk for conventional MV replacement [26]. MV bypass avoids direct manipulation of the severely calcified mitral annulus and involves sewing a conduit from the left atrium (typically the left atrial appendage or left atriotomy incision site) to the left ventricular apex. A prosthetic valve (either bioprosthetic or mechanical) is incorporated in the conduit near the left ventricle. Importantly, this technique cannot be used in patients with significant mitral regurgitation as the conduit only treats MS.

Transcatheter mitral valve replacement — Transcatheter MV replacement is under investigation as a means of treating patients with severe MS who cannot be treated by PMBV and who have prohibitive surgical risk. There is a clear need for minimally invasive MV replacement strategies given the increasing prevalence of advanced age and comorbidities in patients with symptomatic MS, particularly in the population with severe MS due to MAC. In patients with radiation-associated heart disease, extensive calcification of the ascending aorta often makes the risk of surgery prohibitive, leaving limited treatment options.

Transcatheter MV replacement involves insertion of a balloon-expandable or self-expanding transcatheter valve into the MV position while leaving the native MV tissue in place. This can be accomplished via transapical access, surgical transatrial exposure, or via a completely percutaneous transvenous transseptal approach.

Early investigations of balloon-expandable transcatheter valve implantation in patients with severe circumferential MAC have highlighted the challenges associated with implanting transcatheter valves into the complex MV anatomy [27,28]. In the initial multicenter global registry of first generation balloon expandable valve implantation of 116 patients with severe MAC via transapical, transseptal, or transatrial delivery [28]:

●Procedural success (defined as successful valve implantation without procedural mortality or need for a second valve) was achieved in 77 percent of cases, with 30-day mortality rate of 25 percent.

●Complications included the need for a second valve in 14.7 percent and left ventricular outflow tract (LVOT) obstruction in 11.2 percent.

The use of cardiac CT angiography to predict LVOT obstruction risk using 3D modeling techniques allows for measurement of the "neo-LVOT" area, which is the new LVOT space created with a prosthetic valve in the mitral position. A cutoff of less than 190 mm² has been associated with an increased risk of LVOT obstruction [29]. More recent studies have shown improved success and reduction in 30-day mortality rates with transcatheter valve implantation in patients with severe MAC likely attributable to better patient selection and the employment of techniques to reduce LVOT obstruction risk, including preprocedural alcohol septal ablation and surgical resection of the native anterior mitral leaflet [30,31].

The multicenter prospective Mitral Implantation of Transcatheter Valves trial in patients with severe MAC receiving balloon-expandable transcatheter valve implantation demonstrated the following [32]:

●Technical success achieved in 74.2 percent, with LVOT obstruction occurring in three patients (9.6 percent).

●All-cause mortality at 30 days was 16.7 percent. All-cause mortality at one year was 34.5 percent.

●Patients who survived to one year had improvement in symptoms and mean mitral prosthetic gradient of 6.1 mmHg (5.6 to 7.1 mmHg), with no patients having more than mild residual mitral regurgitation.

Further study is needed to determine the optimal imaging-based criteria to determine appropriate candidates for this treatment. Additionally, further study is needed to identify which patients with severe MAC are most likely to derive clinical benefit from valve intervention given the high burden of comorbidities and high one-year mortality observed in this population. Several dedicated transcatheter MV implantation devices are under investigation for treatment of mitral regurgitation, but may eventually be studied for treatment of patients with symptomatic MS at high risk for surgery [18].

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Cardiac valve disease".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Mitral stenosis in adults (The Basics)")

SUMMARY AND RECOMMENDATIONS

●Symptomatic mitral stenosis (MS) is a disabling and eventually lethal disease unless treated with valvotomy or valve replacement. (See 'Introduction' above.)

●For patients with MS with an indication for intervention, the choice among mitral valve (MV) procedures (percutaneous versus surgical approaches) is based largely upon valve pathology and estimated procedural risks and is also impacted by local expertise and availability of interventional and surgical procedures.

•In patients with rheumatic MS with characteristics favorable for percutaneous mitral balloon valvotomy (PMBV), PMBV is preferred to open mitral commissurotomy. (See 'Rheumatic MS' above.)

•Surgery is preferred in the following settings:

-Surgery is usually preferred in patients with congenital MS, since the anatomy is complex, the utility of PMBV may be limited, and catheterization procedures are potentially dangerous. (See 'Congenital MS' above.)

-Open commissurotomy is an appropriate choice in patients with rheumatic MS with suitable valve morphology who are not candidates for PMBV due to valve deformity or calcification, left atrial thrombus, or significant mitral regurgitation. (See 'Use' above.)

-Closed commissurotomy is not recommended in settings in which PMBV or open MV surgery is available, but it is still performed in resource-limited settings. (See 'Closed surgical commissurotomy' above.)

-MV replacement is indicated for operable patients with MS who have a MV not amenable to either PMBV or open commissurotomy (table 1 and figure 1).

•MS due to severe mitral annular calcification (MAC) cannot be treated with PMBV and is associated with high morbidity and mortality when treated with surgical MV replacement. Transcatheter MV replacement is an investigational approach for treatment of MS due to severe MAC that requires further study. (See 'Transcatheter mitral valve replacement' above.)

●PMBV and surgical commissurotomy can be repeated as long as the valve morphology remains favorable. (See 'Repeat commissurotomy' above.)

●Observational studies suggest an association between severe mitral prosthetic valve-patients mismatch (PPM) and increased mortality rates, although a causal relationship has not been established. To reduce the risk of PPM, surgeons implant the largest possible prosthetic valves. If the valve annulus is small, a mechanical prosthetic valve is favored when appropriate, given its lower transvalvular gradients compared with a bioprosthetic valve. (See 'Prosthetic valve-patient mismatch' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Matthew J Sorrentino, MD, FACC, Catherine M Otto, MD, and Edward Verrier, MD, who contributed to an earlier version of this topic review.

The UpToDate editorial staff also acknowledges Bongani Mayosi, MBChB, PhD, FCP(SA) (deceased), who contributed to an earlier version of this topic.