Chronic primary mitral regurgitation: Indications for intervention

INTRODUCTION — Management of patients with chronic primary mitral regurgitation (MR) requires an understanding of the pathophysiology and natural history of the disease (table 1) and the efficacy and timing of treatment, particularly mitral valve repair and replacement.

Primary MR is caused by a primary abnormality of one or more components of the valve apparatus (leaflets, chordae tendineae, papillary muscles, annulus) in contrast to secondary MR, which is caused by other cardiac disease (such as coronary heart disease or a cardiomyopathy) (table 2). Identification of the cause and type (primary or secondary) of MR is required for appropriate management of MR as well as any associated conditions.

Mitral valve prolapse (MVP) is the most common cause of chronic primary MR in resource-abundant countries [1]. Rheumatic heart disease is a prominent cause of primary MR in resource-limited countries (particularly during the first two decades of life), but it is an uncommon cause of MR in resource-abundant countries. (See "Mitral valve prolapse: Clinical manifestations and diagnosis" and "Clinical manifestations and diagnosis of rheumatic heart disease", section on 'Mitral regurgitation'.)

The indications for intervention for severe chronic primary MR caused by MVP are reviewed here. The only effective treatment for severe MR is valve repair or valve replacement [2,3]. Recommendations for treatment of severe chronic primary MR differ from those for severe secondary MR (also known as functional MR).

Related issues are discussed separately:

●(See "Mitral valve prolapse: Clinical manifestations and diagnosis".)

●(See "Mitral valve prolapse: Overview of complications and their management".)

●(See "Natural history of chronic mitral regurgitation caused by mitral valve prolapse and flail mitral leaflet".)

●Other aspects of management of chronic primary MR:

•(See "Chronic primary mitral regurgitation: General management".)

•(See "Mitral valve prolapse: Overview of complications and their management".)

•Further discussion of interventions. (See "Chronic primary mitral regurgitation: Choice of intervention" and "Transcatheter edge-to-edge mitral repair".)

APPROACH TO IDENTIFYING CANDIDATES FOR INTERVENTION

Heart team approach — A multidisciplinary heart team approach (including primary [general] cardiologists, interventional cardiologists, cardiac surgeons, imaging specialists, valve and heart failure specialists, and cardiac anesthesiologists) is recommended for the evaluation and care of potential candidates for mitral valve intervention [2-4].

With better definition of the indication for corrective mitral surgery (valve repair or replacement) and improved surgical procedures, outcomes for patients with severe chronic MR treated surgically have improved, and the threshold for corrective surgery has declined. Transcatheter edge-to-edge mitral repair (TEER) is an option for patients with high or prohibitive surgical risk.

Options for mitral valve intervention include surgical mitral valve repair (preferred if the valve is repairable) and surgical mitral valve replacement. For patients who have high surgical risk or are inoperable, TEER is a potential option. The choice of mitral valve intervention is discussed separately. (See "Chronic primary mitral regurgitation: Choice of intervention".)

Clinical factors — For patients with chronic severe primary MR, optimal timing of intervention for chronic severe MR is determined by a number of factors, including:

●Symptoms – The presence and severity of symptoms (commonly characterized by New York Heart Association functional class (table 3)).

●Severity of MR – Careful quantitation is required given the prognostic importance of MR severity (table 4). (See 'Effective regurgitant orifice' below and "Clinical manifestations and diagnosis of chronic mitral regurgitation", section on 'Identifying the severity of MR'.)

●Acuity of MR – Most patients with primary MR have a chronic course. Patients with flail or partial flail mitral leaflet may have acute or chronic MR. For patients with flail or partial flail mitral leaflet and chronic severe MR, indications for corrective surgery are similar to those for other patients with chronic primary severe MR. Management of acute MR is discussed separately. (See "Acute mitral regurgitation in adults".)

●LV systolic function – Clinically, this is generally assessed by measurement of the left ventricular ejection fraction (LVEF), as well as end-systolic dimension or end-systolic volume [5]. An LVEF >60 percent is normal for patients with chronic MR.

Although LVEF values in the range of 50 to 60 percent are considered to be in a low-normal range in the general population without MR, patients with chronic primary MR and a low-normal LVEF have depressed LV intrinsic contractility, which is associated with suboptimal outcomes [6] after otherwise successful corrective mitral surgery [7].

For end-systolic dimension and end-systolic volume, some consideration of body size should be included in any estimation of LV dimension, since smaller adults are less likely to reach the above criteria. However, simply normalizing for body surface area can lead to misleading conclusions, especially in patients who are overweight. In general, somewhat lower values should be used in very small patients and somewhat higher values in very large patients.

Patients with an LVEF below 30 percent are not likely to have an optimal result with mitral valve surgery, especially if valve replacement is necessary. Such patients may be candidates for TEER. (See "Chronic primary mitral regurgitation: Choice of intervention".)

●Feasibility of surgical mitral valve repair – Surgical mitral valve repair is preferable to mitral valve replacement for most patients with primary MR, regardless of the LVEF. Thus, the threshold for mitral valve surgery is lower for patients with high likelihood of successful surgical mitral valve repair. (See "Chronic primary mitral regurgitation: Choice of intervention".)

●Presence of atrial fibrillation (AF) – The presence of AF (paroxysmal or persistent) is an adverse prognostic factor. (See 'AF or pulmonary hypertension' below.)

●Presence of pulmonary hypertension – The presence of pulmonary hypertension at rest (defined as pulmonary artery systolic pressure >50 mmHg at rest) or with exercise (defined as exercise pulmonary artery systolic pressure >60 mmHg) is an adverse prognostic factor. (See 'AF or pulmonary hypertension' below.)

●Presence of concurrent indication for cardiac surgery (eg, coronary artery bypass surgery).

●Patient preferences and access to follow-up.

The above approach is supported by observational data. (See 'Rationale for intervention' below.)

FOR SYMPTOMATIC PATIENTS

Severe MR — Patients with symptoms attributable to severe chronic primary MR (eg, dyspnea and fatigue) require mitral valve intervention. These patients are candidates for corrective mitral intervention, even if symptoms improve with medical therapy (eg, diuretic therapy) and the LV appears to be compensated [2,3]. Even patients who become asymptomatic with medical management of heart failure face a substantial mortality risk with continued medical management [8], so mitral intervention should not be delayed in these patients.

If there is uncertainty about the presence or absence of symptoms, exercise testing may provide objective information that may not be available from the medical history alone.

The importance of timely intervention in patients with symptomatic severe MR was illustrated by a retrospective study of 481 patients with mitral valve prolapse (MVP) with severe MR with at least one American College of Cardiology/American Heart Association guideline indication for mitral valve surgery compared outcomes with early surgery (performed within two months of presentation with an indication for surgery) with outcomes with late surgery (performed >2 months after presentation with an indication for surgery) [9]. Most of the patients were symptomatic (95 percent in the early surgery group and 87 percent in the late surgery group). In a multivariable model, early surgery was associated with a lower hazard for death compared with late surgery (hazard ratio 0.54, 95% CI 0.30-0.97). Additional data on timing of intervention are discussed below. (See 'Rationale for intervention' below.)

Moderate MR — Because there is considerable variability in the accuracy of quantitation of regurgitation severity, some patients with MVP classified as having less than severe or moderate MR may have hemodynamically severe disease. If symptoms are present, the severity of MR should be carefully reassessed and alternate causes for symptoms should be sought. (See "Clinical manifestations and diagnosis of chronic mitral regurgitation", section on 'Identifying the severity of MR'.)

If no other cause is evident and moderate MR is confirmed, exercise echocardiography is suggested to determine if there is worsening MR and pulmonary hypertension with exercise [10]. Additional work-up includes evaluation for other causes of symptoms, such as heart failure with preserved ejection fraction. (See "Heart failure with preserved ejection fraction: Clinical manifestations and diagnosis".)

If the above evaluation indicates that the cause of symptoms in a patient with confirmed moderate MR is not MR, we suggest watchful waiting with close follow-up. While the risk of mortality and complications with medical management is highest for MVP with severe MR (effective regurgitant orifice area [EROA] ≥0.40 cm²) [11], studies have found that MVP with moderate MR due to mitral valve prolapse (EROA 0.20 to 0.39 cm²) is associated with excess mortality risk [12] and somewhat elevated rates of adverse cardiac events (heart failure, AF) [11]. (See 'Watchful waiting' below.)

FOR ASYMPTOMATIC PATIENTS — For asymptomatic patients with severe chronic MR, the timing of mitral valve surgery is based upon weighing the risk of worsening clinical status (including development of LV systolic dysfunction, pulmonary hypertension, or AF and worsened long-term prognosis with mitral valve surgery) against the operative risk of early mitral valve surgery. Exercise echocardiography may be useful when there is a concern that symptoms may be occurring or there are borderline echocardiographic findings [13].

The following recommendations for intervention are in broad agreement with those in the 2020 American College of Cardiology/American Heart Association and 2021 European Society of Cardiology guidelines [2,3].

With LV systolic dysfunction — For asymptomatic patients with severe chronic MR and evidence of LV systolic dysfunction (defined as LVEF ≤60 percent and/or LV end-systolic dimension [LVESD] ≥40 mm), we recommend mitral valve intervention. (See 'LV systolic dysfunction' below.)

Given the potential risk of missing the onset of LV systolic dysfunction, if there is progressive increase in LVESD (approaching but less than 40 mm) or decrease in LVEF (approaching but greater than 60 percent) on at least three serial studies, more frequent periodic surveillance (at intervals ≤6 months) is warranted. Some patients in this setting may reasonably choose to proceed with mitral valve intervention.

With normal LV function

General approach — For asymptomatic patients with severe chronic MR with normal LV systolic function (LVEF >60 percent, LVESD <40 mm), with high likelihood of successful mitral valve repair (eg, >95 percent), and low expected surgical mortality rate (eg, <1 percent), we suggest surgical mitral valve repair. Successful mitral valve repair is defined as durable repair with less than mild residual MR [14]. Likelihood of repair is based upon valve morphology, surgeon/surgical center volumes and expertise, and their published success rates. Patients with associated pulmonary hypertension and/or AF may be more likely to benefit from valve repair in this setting. (See 'Evidence for early intervention' below and 'AF or pulmonary hypertension' below.)

Estimating the risk of surgical mortality is discussed separately. (See "Estimating the risk of valvular procedures".)

A higher threshold for surgery is used if valve replacement is likely to be required.

The role of watchful waiting as an alternative approach is discussed below. (See 'Watchful waiting' below.)

Watchful waiting — Periodic surveillance is recommended for asymptomatic patients with MVP with chronic moderate or severe MR with normal LV systolic function in whom immediate mitral valve intervention is not planned. This approach is most appropriate for selected carefully followed asymptomatic patients without pulmonary hypertension or AF. (See 'Evidence for early intervention' below.)

It is important to monitor LV size and function in asymptomatic patients with severe MR to prevent the development of irreversible LV dysfunction. In the absence of symptoms, management decisions and the indications for surgery rest largely upon the echocardiographic assessment of LV size and function as well as careful confirmation of the severity of MR.

Patients managed with periodic surveillance should undergo careful monitoring with physical examination and echocardiography every 6 to 12 months or any time symptoms occur [2]. The six-month interval is preferred if stability has not been documented, there is evidence of progression, or measurements are close to the echocardiographic cutoff values. Because there is variability in measurement of LVEF and end-systolic size, any observed interval change should be reconfirmed with another study at a shorter time interval to determine if there is consistent, reproducible change in LV size or systolic function that would warrant intervention. (See "Chronic primary mitral regurgitation: General management", section on 'Monitoring'.)

An occasional patient with a borderline LVEF or a technically limited echocardiographic study will require radionuclide, contrast angiography, or cardiovascular magnetic resonance imaging to assess LV function and regurgitant fraction. Exercise stress testing may add objective evidence about symptoms and a change in exercise tolerance. Measurement of MR severity and pulmonary artery pressure during exercise may also be helpful [15]. (See "Tests to evaluate left ventricular systolic function" and "Chronic primary mitral regurgitation: General management", section on 'Exercise testing'.)

Surgery may be offered earlier in patients with borderline LV systolic function in whom access to close monitoring is limited.

Some degree of LV and left atrial enlargement are expected in severe chronic MR. LV diastolic chamber enlargement is generally not an indication for surgery in patients with severe chronic MR; diastolic LV size is load-dependent, whereas end-systolic size better reflects LV systolic function.

Concomitant cardiac surgery — The rationale for performing concomitant mitral valve surgery (repair or replacement) in patients with chronic severe primary MR undergoing cardiac surgery for other indications is that mitral valve surgery is likely to be required eventually and the risk of a single operation is lower than the risk of two operations. Early and late survival rates are higher after mitral valve repair with aortic valve replacement than following double valve replacement [16].

For asymptomatic patients with chronic severe primary MR undergoing cardiac surgery for other indications, we recommend concomitant mitral valve surgery (generally repair).

RATIONALE FOR INTERVENTION — Randomized trials have not been performed comparing medical therapy to mitral valve surgery or transcatheter edge-to-edge mitral repair in patients with severe chronic primary MR. Recommendations for mitral valve surgery in patients with chronic primary MR are based upon observational data, including comparisons of natural history data with outcomes when surgery is performed in response to symptoms and other clinical findings.

Natural history — Primary MR is caused a mechanical problem affecting mitral leaflet coaptation and the natural history of severe chronic primary MR is characterized by a progression from a compensated phase to transitional and decompensated phases (table 1) [2]. Progression to severe MR occurs more often in patients with baseline MR, and the more baseline MR, the more MR progression is noted (MR begets MR) [17]. Progression of the regurgitant volume is determined by progression of mitral annular dilatation and progression of lesions such as a new flail leaflet due to chordal rupture [18]. MR progression is associated with progression of LV and left atrial remodeling.

For patients 50 years or older with chronic primary MR treated medically, the estimated annual mortality rate is approximately 3 percent for moderate MR and 6 percent for severe MR [19]. Patients with severe chronic primary MR have annual cardiac event rates of approximately 10 to 12 percent (including an approximately 9 percent risk of heart failure and 5 percent risk of AF). Predictors of adverse outcomes include symptoms, depressed LVEF, increased LV end-systolic dimension (LVESD), older age, pulmonary hypertension, AF, left atrial dilation, and greater effective regurgitant orifice area (EROA) [2,3,19]. Among medically treated patients with severe chronic primary MR, the risk of sudden death ranges from approximately 1 percent per year in asymptomatic patients with normal LVEF to 8 percent per year in patients with class III or IV symptoms and flail mitral leaflet with severe MR [19]. (See "Mitral valve prolapse: Overview of complications and their management", section on 'Ventricular arrhythmias and sudden cardiac death'.)

Timing of mitral intervention — For patients with severe primary MR, the timing of mitral intervention is based upon weighing the progressive risks of morbidity and mortality with continued medical management against the risks of mitral valve intervention.

The importance of surgical repair before there is a significant impairment in LV function or more than mild symptoms was suggested by a report of 409 patients who underwent surgery for isolated organic MR [6]. Ten-year survival was 72, 53, and 32 percent in patients with a preoperative LVEF of ≥60 percent, 50 to 59 percent, and less than 50 percent, respectively. Among patients with an LVEF ≥60 percent, survival was higher in patients with New York Heart Association class I or II compared with class III or IV (82 versus 59 percent).

Early mortality after mitral valve surgery varies from approximately 1 percent for patients less than 65 years old, 2 percent for patients 65 to 75 years old, to 4 to 5 percent for patients greater than 75 years old [19]. The risks of mitral valve intervention are discussed in detail separately. (See "Chronic primary mitral regurgitation: Choice of intervention".)

Effective regurgitant orifice — The predictive value of a large EROA was suggested by a prospective observational study of 465 patients with isolated primary MR (80 percent mitral valve prolapse), a normal LVEF (mean 70 percent), absence of pulmonary hypertension, and, in all but 9 percent, absence of AF [11]. An EROA ≥40 mm², which was present in 43 percent of cases, was associated with a larger regurgitant volume (101 versus 29 mL/beat with an EROA <20 mm²) and was a powerful predictor of an adverse outcome, including all-cause mortality, cardiac events, and undergoing cardiac surgery.

Similarly, a prospective observational study of 447 asymptomatic patients with severe MR and normal LV function found that EROA, baseline grade of pulmonary hypertension, and age were independent predictors for development of an indication for MV surgery or heart failure [20].

An important concern regarding use of EROA is that quantitation of EROA is technically difficult and thus requires appropriate training and experience. Another key issue is that EROA does not account for the duration of regurgitation (mid-late systolic versus holosystolic), which likely explains why regurgitant volume rather than EROA predicted outcomes in one large series [21]. Eccentric MR jets are also more difficult to assess using echocardiographic measures. These issues are discussed in more detail separately. (See "Natural history of chronic mitral regurgitation caused by mitral valve prolapse and flail mitral leaflet", section on 'Clinical outcome'.)

An additional issue complicating quantitation of MR is that the severity of MR varies with hemodynamic conditions (loading conditions and inotropic state) [22]. The dynamic nature of MR explains variations in the degree of MR with general anesthesia and in some patients presenting with acute pulmonary edema [15,23].

Predictive value of high risk features — The presence of one or more high risk features (LV dysfunction [defined as LVEF ≤60 percent or LVESD ≥40 mm], pulmonary hypertension [defined as resting pulmonary artery systolic pressure >50 mmHg or exercise pulmonary artery systolic pressure >60 mmHg] and AF) is associated with adverse outcomes.

LV systolic dysfunction — For patients with severe MR and LV systolic dysfunction, there are limited data comparing mitral intervention versus continued medical management, as these patients are generally referred for mitral valve surgery (surgical valve repair when feasible).

As noted above, progressive MR is associated with progressive adverse LV remodeling with LV systolic dysfunction. Patients with severe MR with an LVEF ≤60 percent or LVESD ≥40 mm have already developed systolic dysfunction [24-27]. Serial echocardiographic studies have shown that preoperative LVESD ≥40 to 45 mm or a low-normal (50 to 60 percent) or abnormal/depressed LVEF (<50 percent) is predictive of persistent postoperative LV enlargement and systolic dysfunction and reduced late survival rates [6,25,28-30]. A study of patients with severe MR undergoing mitral valve repair found that a preoperative LVEF ≥64 percent with LVESD <37 mm predicted low risk of postoperative LV dysfunction (9 percent) compared with preoperative LVEF <64 percent or LVESD ≥37 mm (21 percent), and preoperative LVEF <64 percent and LVESD ≥37 mm (33 percent) [25].

Among patients with primary MR with flail leaflet, the presence of reduced LV function (along with severity of symptoms) is a risk factor for sudden death, and surgical correction is associated with substantially reduced risk of sudden death [31].

AF or pulmonary hypertension — For patients with asymptomatic severe MR with normal LV systolic function, the risk of adverse outcomes with continued medical management is higher in patients with AF or pulmonary hypertension. Observational data suggest improvement in outcomes with mitral intervention (mitral valve repair) in asymptomatic patients with severe MR and normal LV systolic function, particularly those with AF or pulmonary hypertension [32].

Among 2425 patients with mitral valve prolapse (MVP) and MR, the presence of AF was independently associated with excess mortality risk (10-year survival in sinus rhythm and in paroxysmal AF and persistent AF was 74, 59, and 46 percent, respectively) and mitral valve surgery (88 percent repair) was associated with reduced risk [33]. However, postsurgical outcome was affected by AF (10-year postsurgical survival in sinus rhythm and in paroxysmal and persistent AF was 82, 70, and 57 percent).

In a study of 78 patients with MVP and at least moderate MR, two-year symptom-free survival was reduced in patients with resting pulmonary hypertension (36 versus 59 percent) or exercise pulmonary hypertension (38 versus 75 percent) [15]. Exercise pulmonary hypertension (but not resting pulmonary hypertension) was an independent predictor of symptom occurrence.

The following section discusses a meta-analysis in which a survival benefit was associated with early surgery (versus watchful waiting) in asymptomatic patients with normal LV systolic function, particularly those with AF or pulmonary hypertension [32].

Evidence for early intervention — Observational data suggest that patients with severe chronic primary MR have better outcomes when mitral valve intervention (surgical mitral valve repair when the valve is repairable) is performed early (ie, when there is a high probability of mitral valve repair and no other indications) than after the development of symptoms, heart failure, LV systolic dysfunction, pulmonary hypertension, or AF, although these data are subject to limitations [2,3,11,20,24,34-38].

In patients with severe chronic primary MR with no or mild symptoms, surgery appears to restore life expectancy to expected levels (similar to the age- and sex-matched general population) while excess mortality risk remains in patients with moderate or severe symptoms [34,39]. Clinical progression with occurrence of new symptoms and complications such as heart failure, LV systolic dysfunction, or AF is associated with excess mortality with medical management, which is alleviated but not completely eliminated by mitral surgery [24,33,34,40-43]. (See "Natural history of chronic mitral regurgitation caused by mitral valve prolapse and flail mitral leaflet", section on 'Mitral regurgitation' and "Mitral valve prolapse: Overview of complications and their management", section on 'Ventricular arrhythmias and sudden cardiac death'.)

A systematic review evaluated observational studies comparing early intervention with watchful waiting in asymptomatic patients with severe chronic MR [32] including five observational studies [11,20,35,37,38]; three of the five studies were included in pooled analysis (with mean follow-up of 7.5 to 10.3 years) [20,35,38]:

●In the three studies of asymptomatic patients with normal systolic function with both early surgery and watchful waiting arms, 10- to 12-year survival was 89 percent to 91 percent in the early surgery (most undergoing mitral valve repair) cohort and 62 to 88 percent in the watchful waiting cohort (hazard ratio 0.46, 95% CI 0.24-0.88). In a subgroup of these patients without AF or pulmonary hypertension, some survival benefit of early surgery persisted (risk ratio [RR] 0.85, 95% CI 0.75-0.98).

●All five studies reported operative mortality rates ≤1 percent (aggregate mortality rates of 0.7 percent for both early surgery and watchful waiting cohorts).

●For the three pooled studies, early surgery was associated with a higher rate of mitral valve repair versus replacement (RR 1.10, 95% CI 1.02-1.18).

Similar results were reported in a single-center study of 1512 patients with primary MR who underwent mitral valve surgery [24]; this study partially overlapped two studies included in the above systematic review. Long-term survival was lower in patients who underwent surgery for class I triggers (heart failure symptoms, LVEF <60 percent, or end-systolic dimension ≥40 mm) and for class II triggers based upon complications (AF or pulmonary hypertension), compared with those with a class II trigger based upon the combination of severe MR and high probability of valve repair (15-year survival rates of 42 and 53 versus 70 percent).

A limitation of the above studies is that mitral valve surgery was not performed in all patients in the watchful waiting group who developed indications for surgery and, when performed, the timeliness of surgery was not specified. Since the meta-analysis was based upon observational data, residual confounding cannot be excluded. In addition, the early surgery approach is applicable only to centers with similarly high rates of successful mitral valve repair and low rates of operative mortality.

Recommendations for watchful waiting are presented above. (See 'Watchful waiting' above.)

Severely impaired left ventricular function — A separate issue is mitral valve intervention in patients with severe chronic primary MR and severe LV dysfunction (LVEF <30 percent and/or LVESD >55 mm) in whom mitral valve intervention may improve symptoms but may not alter long-term mortality rates or need for LV assist device support or transplantation. Such patients with primary mitral valve disease generally exhibit irreversible depression of ventricular contractility due to long-standing LV volume overload. LV systolic function does not improve after mitral valve surgery. For selected patients with severe MR with LVEF <30 percent who have a high likelihood of durable repair and low comorbidity, the potential benefit of mitral valve surgery with attempted repair may exceed the risk. Transcatheter edge-to-edge mitral repair is an option for selected patients with high or prohibitive operative risk, as discussed separately. (See "Chronic primary mitral regurgitation: General management", section on 'Treatment of heart failure' and "Chronic primary mitral regurgitation: Choice of intervention".)

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".)

SUMMARY AND RECOMMENDATIONS

●General approach – The timing of corrective surgery for chronic severe primary mitral regurgitation (MR) is determined by a number of factors, including the presence or absence of symptoms, the severity and acuity of MR, the functional state of the left ventricle (LV), the feasibility of valve repair, the presence of atrial fibrillation (AF), the presence of pulmonary hypertension, comorbidities, and the preferences of the patient. (See 'Approach to identifying candidates for intervention' above.)

●Symptomatic patients with severe MR – Patients with symptoms attributable to chronic severe primary MR require intervention (mitral valve surgery or transcatheter repair). Chronic severe primary MR is a progressive disorder which requires intervention for correction. (See 'Severe MR' above and 'Rationale for intervention' above.)

●Asymptomatic patients with severe MR

•With LV systolic dysfunction – For asymptomatic patients with severe chronic MR and LV systolic dysfunction (defined as LV ejection fraction [LVEF] ≤60 percent and/or LV end-systolic dimension [LVESD] ≥40 mm) we recommend mitral valve intervention (Grade 1B). (See 'LV systolic dysfunction' above.)

Given the potential risk of missing the onset of LV systolic dysfunction, if there is progressive increase in LVESD (approaching but less than 40 mm) or decrease in LVEF (approaching but greater than 60 percent) on at least three serial studies, more frequent periodic surveillance (at intervals ≤6 months) is warranted. Some patients in this setting may reasonably choose to proceed with mitral valve intervention.

•Severe MR with normal LV function – For asymptomatic patients with severe chronic MR with normal LV systolic function (LVEF >60 percent, LVESD <40 mm), with high likelihood of successful mitral valve repair, and with low expected surgical mortality rate, we suggest surgical mitral valve repair. Patients with associated pulmonary hypertension and/or AF may be more likely to benefit from valve repair in this setting. (Grade 2C). (See 'With normal LV function' above and 'Evidence for early intervention' above.)

Watchful waiting is a reasonable alternative to mitral valve repair in low-risk asymptomatic patients who can be closely followed. This involves serial clinical follow-up and repeat echocardiograms (and other imaging if needed) at 6- to 12-month intervals to determine if there are changes in clinical status that would warrant intervention. (See 'Watchful waiting' above and 'Evidence for early intervention' above.)

•Concurrent indication for cardiac surgery – For patients with chronic severe primary MR with no symptoms attributable to MR undergoing cardiac surgery for other indications, we recommend concomitant mitral valve repair (Grade 1B). (See 'Concomitant cardiac surgery' above.)

●Less than severe MR - Chronic MR which is less than severe is managed with watchful waiting unless there is a concurrent indication for cardiac surgery. (See 'Moderate MR' above and 'Watchful waiting' above.)

ACKNOWLEDGMENTS — The UpToDate editorial staff acknowledges Sorin Pislaru, MD, who contributed to earlier versions of this topic review.

The UpToDate editorial staff also acknowledges William H Gaasch, MD (deceased), who contributed to earlier versions of this topic.