Surgical procedures for severe chronic mitral regurgitation

INTRODUCTION — Modern management of patients with chronic mitral regurgitation (MR) requires an understanding of multiple factors. These include:

●The pathophysiology and natural history of the disease

●The severity of the valvular lesion

●The presence or absence of atrial fibrillation (AF)

●The indications for mitral valve repair and mitral valve replacement

The only effective treatment is surgical valve repair or valve replacement [1,2].

Surgical procedures for severe chronic MR will be reviewed here. The indications for corrective surgery in chronic MR, an overview of the natural history and management of chronic MR, and issues related to mitral valve prolapse, ischemic MR, functional MR, and MR in elderly patients are discussed separately. (See "Chronic primary mitral regurgitation: Indications for intervention" and "Natural history of chronic mitral regurgitation caused by mitral valve prolapse and flail mitral leaflet" and "Chronic primary mitral regurgitation: General management" and "Valvular heart disease in older adults" and "Chronic secondary mitral regurgitation: General management and prognosis".)

PREOPERATIVE CONSIDERATIONS — Indications for mitral valve surgery in patients with chronic primary or secondary MR are discussed separately. (See "Chronic primary mitral regurgitation: Indications for intervention".)

Two surgical mitral valve procedures are available for the treatment of chronic MR: valve repair and valve replacement. The choice of procedure depends, at least in part, upon the cause of the MR, the anatomy of the mitral valve, and the functional status of the left ventricle [1]. (See 'Valve repair versus valve replacement' below.)

Surgical risk stratification — The most effective way of stratifying operative risk is by using one of the available validated risk stratification models. As noted above, a variety of factors affect the risk of mortality after aortic valve replacement. The risk models are helpful in the evaluation and counseling of individual patients and planning perioperative care. Models have been developed to estimate risk of in-hospital mortality and complications following mitral or aortic valve surgery with or without coronary artery bypass graft surgery (CABG). These are discussed separately. (See "Estimating the risk of valvular procedures".)

Evaluation for coronary disease — Many patients with nonischemic chronic MR requiring surgery also have significant coronary artery disease. The prevalence of coronary disease in patients with degenerative mitral valve disease/prolapse (the most common cause of nonischemic MR) was evaluated in a study in which routine coronary angiography was performed before surgery in 722 patients (67 percent men, mean age 61 years) who did not have a history of myocardial infarction, ischemic electrocardiographic changes, or angina [3]. Obstructive (≥50 percent) coronary lesions in one or more major vessels were present in 19 percent of patients.

Obstructive coronary lesions are usually revascularized at the time of mitral valve surgery; concurrent bypass surgery typically adds little morbidity or mortality to the procedure [1]. A separate issue, which is discussed elsewhere, is the management of ischemic MR. (See "Chronic secondary mitral regurgitation: General management and prognosis".)

The American College of Cardiology/American Heart Association and the European Society of Cardiology guidelines on the management of valvular heart disease included recommendations for the use of coronary angiography to establish the presence or absence of coronary disease prior to valve surgery [1,2]. Assuming that the patient is not hemodynamically unstable, coronary angiography was recommended prior to valve intervention in patients who have or are suspected to have coronary disease and in those with coronary risk factors. Individuals with coronary risk factors include men >40 years of age and postmenopausal women. Based upon these recommendations, many patients without significant coronary disease will undergo coronary angiography. Better methods are needed to identify patients at low risk.

A possible alternative is noninvasive coronary angiography, which may be accomplished using computed tomography (CT) or magnetic resonance imaging. The potential utility of these tests as an alternative to conventional selective coronary angiography is discussed separately. Further study is required before this approach can be recommended. (See "Cardiac imaging with computed tomography and magnetic resonance in the adult".)

VALVE REPAIR

Valve repair outcomes — Mitral valve repair procedures, called mitral valvuloplasties, are usually preferred for the surgical treatment of MR. Techniques for mitral valve repair include annuloplasty ring implantation, leaflet resection/remodeling, neochordae implantation, and edge-to-edge (Alfieri) repair. With routine use of multiple techniques, the repairability of AL and bileaflet pathologies is approaching that for isolated (P2) PL prolapse. Mitral valve repair techniques, with use of adjunctive artificial chord replacement and ring annuloplasty (with ring prosthesis such as Carpentier Edwards or Duran ring), have significantly expanded the scope and durability of repair, especially in patients with bileaflet and anterior leaflet prolapse [4,5].

The following discussion is related to valve repair for primary MR (degenerative disease, prolapse, and flail leaflet).

Mitral valve repair for degenerative MR has two major benefits:

●It preserves all functional components of the native valve, and as a result, repair is associated with better postoperative ventricular function than seen with valve replacement.

●It avoids the use of a prosthetic heart valve with its attendant complications. (See "Mechanical prosthetic valve thrombosis or obstruction: Clinical manifestations and diagnosis".)

Patient outcomes after mitral valve repair are excellent when performed at experienced centers. In a review from the Cleveland Clinic of 1072 patients who underwent mitral valve repair for MR due to degenerative disease, the in-hospital mortality was 0.3 percent [6]. In the Mayo series of 1173 patients undergoing mitral valve repair for mitral valve prolapse from 1980 to 1999, 30-day mortality was 0.7 percent, five-year mortality was 11.3 percent and 10-year mortality was 29.4 percent [5]. The 5- and 10-year mortality rates were similar to the expected mortality rates in a normal age-matched population (13.5 percent and 28.4 percent).

Recurrent MR — Recurrent MR, which may require reoperation, is a potential limitation of mitral valve repair. However, in experienced centers, the rate of freedom from reoperation after mitral valve repair is similar to that after mitral valve replacement. (See 'Valve repair versus valve replacement' below.)

The frequency of recurrent MR and reoperation, in patients with primary MR, are illustrated by the following findings:

●In a review from Leuven, Belgium of 242 patients, the prevalence of moderate-severe to severe (3+ to 4+) MR at one month, five years, and seven years was 2, 17, and 29 percent, respectively [7] The prevalence of at least moderate (2+ to 4+) MR at one month, five years, and seven years was 6, 41, and 73 percent. Surgical techniques associated with a greater risk of recurrent MR included lack of use of an annuloplasty ring, the use of chordal shortening instead of artificial chordae or transposition, and lack of use of a sliding plasty for posterior annulus dilatation.

●In a review from Toronto of 701 patients, freedom from recurrent moderate or severe MR at 12 years was significantly higher with posterior compared with bileaflet or anterior prolapse (80 versus 67 and 65 percent, respectively) [8]. The rate of reoperation at 12 years was highest with anterior prolapse (12 versus 4 and 6 percent with posterior and bileaflet prolapse) [8].

●In the Cleveland Clinic experience, freedom from reoperation after 10 years was 93 percent [6]. Reoperation for late mitral valve dysfunction was due to progressive degenerative disease in one-half of these cases. Repair durability was greatest in patients with isolated posterior leaflet prolapse who had posterior leaflet resection and annuloplasty.

●In the Mayo Clinic experience, the risk of reoperation after mitral valve repair was lower in the second decade of the study [5]. For patients undergoing surgery during the 1990s, the linearized risk of reoperation was lowest for isolated posterior leaflet repair (0.50 percent per year), intermediate for bileaflet repair (0.92 percent per year), and highest for anterior leaflet repair (1.64 percent per year), although these rates were not statistically different.

The improvement in durability of anterior leaflet repair in the Mayo experience was attributed to changes in technique [5]. In the 1980s at the Mayo Clinic, anterior leaflet prolapse was corrected by chordal shortening, chordal transfer, or commissural annuloplasty. In the 1990s, anterior leaflet repair was performed by posterior annuloplasty or insertion of polytetrafluoroethylene (Gore-Tex) neochordae, or limited triangular resection. In the Toronto experience, use of neochordae since the 1990s was cited as the single most important factor in making mitral valve repair feasible in most patients with MR with degenerative disease [8].

Intraoperative transesophageal echocardiography is recommended since it can enhance the success of valve repair and can reliably predict early and late mitral valve dysfunction [1,2,9]. (See "Transesophageal echocardiography in the evaluation of mitral valve disease", section on 'Role of intraoperative transesophageal echocardiography'.)

Atrial fibrillation — Atrial fibrillation (AF) is an adverse prognostic factor in patients with MR and is associated with worse long-term outcomes after mitral valve repair for degenerative MR. Patients with AF tend to be older and are more likely to have left ventricular dysfunction.

There are conflicting data as to whether AF is [10] or is not [11] an independent predictor of survival after mitral valve repair. However, patients with AF are at increased risk for mortality due to cardioembolic events [10]. AF is unlikely to resolve after valve repair alone; as a result, a concurrent AF ablation procedure may be considered. (See "Atrial fibrillation: Surgical ablation".)

Percutaneous repair — Methods for percutaneous mitral valve repair to treat MR are under investigation [12].

The possible role of percutaneous mitral valve repair in chronic ischemic MR is discussed separately.

VALVE REPAIR VERSUS VALVE REPLACEMENT

Comparison of outcomes — A number of retrospective studies have demonstrated improved left ventricular (LV) function and survival in patients with chronic primary MR undergoing valve repair compared with valve replacement with or without subvalvular (chordal) preservation (figure 1) [13-19]. The following illustrative findings were reported from a cohort of 47,279 patients aged 65 years or older who underwent primary isolated mitral valve surgery between 2000 and 2009 with a median follow-up of five years [19]:

●Operative mortality was 3.9 percent for patients who had mitral valve repair compared with 8.9 percent in those who had mitral valve replacement.

●One-, five-, and 10-year Kaplan-Meier survival estimates were greater among those who underwent mitral valve repair (91, 77, and 54 percent versus 83, 65, and 37 percent, respectively, for mitral valve replacement).

●The one-, five-, and 10-year survival benefits with mitral valve repair were also seen in those aged 75 years or greater (88, 71, and 40 percent survival with repair versus 80, 60, and 28 percent survival with replacement). (See "Valvular heart disease in older adults", section on 'Mitral valve repair'.)

By contrast, among patients with ischemic MR (a type of secondary MR), survival is similar following mitral valve replacement with chordal sparing and mitral valve repair. However, recurrent MR is more frequent following mitral valve repair. A randomized trial found that mitral valve repair resulted in a significantly higher rate of cardiovascular admission and a borderline significantly higher rate of heart failure-related adverse events, as discussed separately.

Reoperation — The long-term rates of reoperation (not simply recurrent MR) appear to be similar with valve repair and valve replacement.

●In the Emory experience of patients undergoing surgery between 1984 and 1997, the rate of reoperation for mitral valve replacement at five years was 6 percent for patients who had undergone mitral valve repair and 4 percent for those who had undergone mitral valve replacement [17]. However, at the end of 10 years, rate of reoperation was lower in the mitral repair patients (22 percent) compared with mitral replacement patients (34 percent).

●Lower rates of reoperation were noted in a cohort of patient undergoing mitral valve surgery during a slightly later time period. In the Mayo experience for initial repairs in the 1990s, the linearized risk of reoperation after repair of the posterior leaflet (0.5 percent per year) compared favorably to the risk of reoperation after mechanical valve replacement (0.7 percent per year) and all mitral valve replacements (0.7 percent per year) [5]. The risk of reoperation following bilateral and anterior leaflet repair were higher (0.92 and 1.64 percent per year), although not statistically different.

The lower rates of reoperation following mitral valve repair in later series probably reflect the use of more effective anterior leaflet prolapse repair techniques (such as PTFE chordal replacement) [5,8] (see 'Recurrent MR' above). Other possible explanations for the improvement include other technical advances, greater experience, and earlier patient referral.

Based upon such observations, both the 2020 American College of Cardiology/American Heart Association guidelines and the 2021 European Society of Cardiology valve guidelines concluded that mitral valve repair is preferred in the majority of patients with chronic primary MR and should be performed at centers experienced in this procedure [1,2]. Because of the lower risk, surgery can be performed earlier when repair is feasible (and considered highly likely).

Catheter-based procedures (transcatheter edge-to-edge repair and valve-in-valve transcatheter mitral valve implantation) enable treatment of many patients with late postintervention valve dysfunction, so that not all will require open surgical reinterventions.

Cause of MR — The feasibility and outcomes of mitral valve repair, as opposed to replacement, is related to the anatomic cause of the MR. This was illustrated in a series of 248 patients who underwent surgery for MR at the Mayo Clinic [20]:

●Mitral valve prolapse was associated with an operative mortality of 1.7 percent; 90 percent underwent valve repair. The five-year survival was 86 percent and the five-year rate of heart failure was 13 percent. The risk of recurrent MR is discussed above. (See 'Recurrent MR' above.)

●Primary, nonprolapse mitral valve disease (due to rheumatic heart disease, endocarditis, or miscellaneous causes) had a 5.7 percent operative mortality; 63 percent underwent valve repair. The five-year survival was 69 percent and the five-year rate of heart failure was 16 percent. Issues related to surgery in patients with endocarditis are discussed separately. (See "Surgery for left-sided native valve infective endocarditis".)

●Secondary MR (including ischemic MR) was associated with a 16 percent operative mortality; 75 percent had valve repair. The five-year survival was 50 percent and the five-year rate of heart failure was 38 percent. Issues related to ischemic and functional MR are discussed separately. (See "Chronic secondary mitral regurgitation: General management and prognosis".)

Valve anatomy on echocardiography — Preoperative echocardiography can identify structural features that aid in selection of the appropriate surgical procedure [20,21]. Echocardiographic parameters that predict failure of annuloplasty in ischemic MR are discussed elsewhere.

In a prospective study published in 1997, 350 patients who were to undergo mitral valve surgery for MR had preoperative transthoracic and transesophageal echocardiography [21]. Repair, rather than replacement, was recommended if the following features were present:

●Limited calcification of the leaflets or annulus

●Prolapse of less than one-third of either leaflet

●Pure annular dilatation

●Valvular perforations

●Incomplete papillary muscle rupture

Repair was less likely to be successful so that replacement was indicated if the following conditions existed:

●Extensive calcification or degeneration of a leaflet or annulus

●Prolapse of more than one-third of the leaflet tissue

●Extensive chordal fusion, calcification, or papillary muscle rupture

Transthoracic and transesophageal echocardiography were equally accurate in predicting the surgical procedure to be performed. A subsequent study suggested that transesophageal echocardiography was slightly better overall but that the benefit was more pronounced in patients with mediocre transthoracic images or flail leaflets [20].

Preoperative transesophageal echocardiography is helpful in determining the likelihood of valve repair when this factor would affect the timing of surgical intervention. When surgery is indicated regardless of valve repairability, preoperative transesophageal echocardiography is needed only when the transthoracic images are not diagnostic. In contrast, transesophageal echocardiography is essential in the operating room to better define the anatomy, ensure an adequate repair, and confirm the absence of complications after repair [1].

Left ventricular dysfunction — Patients with severe left ventricular dysfunction are at increased risk of mortality from mitral valve surgery, both in terms of perioperative and long-term survival [14].

Data comparing valve repair with valve replacement in patients with left ventricular dysfunction are limited. Mitral valve repair has been preferred to replacement in this setting because of the comparable or better survival figures, despite the frequent persistence or recurrence of MR. The data supporting this approach are discussed elsewhere. When valve replacement is required, it is important to preserve the chordal mechanism to preserve or improve left ventricular function and geometry.

VALVE REPLACEMENT — There are several issues that must be addressed when valve replacement is considered. These include the choice of a mechanical versus bioprosthetic valve and, if possible, chordal preservation.

Mechanical versus bioprosthetic valves — Both mechanical and bioprosthetic valves can be used for replacement of a mitral valve. The major problems associated with mechanical valves are thromboembolism and/or bleeding from the chronic anticoagulation that is required to prevent thromboembolism. A most important problem with bioprosthetic valves is limited durability due to valve degeneration, particularly among those <65 years old. These issues are discussed separately. (See "Choice of prosthetic heart valve for surgical aortic or mitral valve replacement".)

Chordal preservation — Valve replacement with excision of the subvalvular apparatus is necessary when there is severe leaflet disease with subvalvular scarring and calcification. This procedure generally has a negative impact on left ventricular function, as shown in both experimental animals and humans; it may be due in part to severing of the chordae tendineae [22-25].

If possible, valve replacement with preservation of the subvalvular apparatus is preferred (figure 2). This procedure provides a competent valve, preserves the functional components of the subvalvular apparatus, improves left ventricular (LV) geometry and long-term function, and produces a better clinical outcome than valve replacement alone [24,26]. In a comparative study, for example, the LV ejection fraction (EF) decreased from 60 percent preoperatively to 36 percent postoperatively in seven patients who had had chordal transection; by comparison, the preoperative and postoperative ejection fractions were similar (63 and 61 percent) in the eight patients who had chordal preservation [24].

The authors attributed the improved results with chordal preservation to a smaller LV size that results in lower systolic wall stress [24,27]. Preservation of LV long axis shortening and an ellipsoid (versus spherical) LV shape may also contribute to more effective LV systolic function [28]. This can be particularly important in patients with decompensated MR, in whom attempts should be made to avoid or minimize a postoperative decline in ventricular function.

Prosthetic valve-patient mismatch — Prosthetic-patient mismatch (PPM) is defined as a prosthetic valve size that is small in relation to the patient’s body size. This is commonly defined as the effective orifice area (EOA) indexed to body surface area (EOA index [EOAI]). PPM is common in patients undergoing mitral valve replacement and may be associated with transvalvular pressure gradients similar to mild to moderate mitral stenosis. Normalization of pulmonary artery pressure is a goal of mitral valve replacement since even mild pulmonary hypertension can impair exercise capacity and may increase morbidity and mortality. PPM may contribute to persistent postoperative pulmonary hypertension [29,30].

An association between PPM and reduced postoperative survival was reported by two single-center retrospective studies from Canada [31,32]; in contrast, a third study found no relationship between PPM and survival:

●In the Quebec study of 929 patients who underwent mitral valve replacement, the EOAI was used to define PPM as severe when ≤0.9 cm²/m² (9 percent), moderate (69 percent of patients) when >0.9 and ≤1.2 cm²/m², and nonsignificant when >1.2 cm²/m² (22 percent) [31]. Patients with severe PPM had 6- and 12-year survivals that were lower than those for 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). PPM was associated with higher pulmonary artery pressures.

●In the Ottawa study of 884 patients who underwent mitral valve replacement, PPM, defined as an EOAI of ≤1.25 cm²/m², was present in 32 percent [32]. Survival for patients with PPM was significantly lower compared with those without PPM at all-time points ranging from 91 versus 95 percent at one year to 65 versus 75 percent at 10 years.

●In contrast, a study from Vancouver found no association between PPM and overall mortality [33]. Among 2440 patients who had undergone mitral valve replacement, 14 percent had no PPM, 70 percent had moderate PPM, and 16 percent had severe PPM (categories defined as in the Quebec study). Survival to 15 years was not significantly different among patients with no, moderate, or severe PPM. The EOAI was an independent predictor of early mortality but not of late or overall mortality. There was interaction between EOAI and pulmonary hypertension (which was an independent predictor of overall mortality).

Limitations of these studies include lack of partitioning of results for patients with MR from those for patients with mitral stenosis [34,35]. There were large differences in the frequency of PPM (78 percent, 32, and 86 percent) in the three studies, which may have been partly due to the lower proportion of smaller prostheses in the Ottawa study as well as differing normal reference values for EOA in the Ottawa study.

In addition, it is not clear that the association between PPM and pulmonary hypertension is causal. Patients requiring smaller prosthetic valve sizes (eg, <27 mm) frequently have heavily calcified mitral annuli and longstanding mitral disease likely to predispose to persistent pulmonary hypertension. Therefore, PPM may reflect patient specific risk factors rather than a prosthetic valve problem.

Despite these limitations, evidence that PPM is associated with residual pulmonary hypertension and increased mortality provides a rationale for implanting a mitral valve prosthesis with largest EOA for a given annulus size; the inability to completely avoid PPM provides further support for the strategy of repairing rather than replacing the valve, when possible [30,35]. (See 'Valve repair versus valve replacement' above.)

Hospital volume and outcome — There is a modest relationship between short-term outcome after mitral valve replacement and the volume of procedures performed at the hospital. This was illustrated in a review of the Medicare database, which found that the adjusted in-hospital and 30-day mortality was inversely related to volume, ranging from 11.6 percent in hospitals performing >199 procedures per year to 15 percent in those performing <43 per year [36].

Minimally invasive surgery — There are only limited data on the use of minimally invasive mitral valve surgery in patients with chronic MR. This issue is discussed separately. (See "Minimally invasive aortic and mitral valve surgery".)

CONCURRENT TRICUSPID REGURGITATION — Significant tricuspid regurgitation is common at the time of and following mitral valve surgery. Prognostic significance and management of tricuspid regurgitation (including concurrent tricuspid valve surgery at the time of mitral valve surgery) is discussed separately. (See "Management and prognosis of tricuspid regurgitation".)

MANAGEMENT OF ATRIAL FIBRILLATION — Patients with chronic MR who undergo valve repair or replacement often have concomitant atrial fibrillation (AF). While valve surgery improves hemodynamic status, AF usually persists.

Several intraoperative procedures have been developed to manage AF at the time of mitral valve surgery, either by preventing recurrence of the arrhythmia or by reducing the embolic risk. A number of studies have demonstrated the efficacy of performing a combined procedure that includes either a maze procedure or radiofrequency or cryoablation in addition to mitral valve surgery. Any of these procedures reduces the frequency of persistent AF without a significant increase in operative complications. The data supporting these approaches are presented separately. The potential utility of mitral valve repair combined with surgical maze to treat patients with new-onset AF with moderate MR has not been evaluated. (See "Atrial fibrillation: Surgical ablation", section on 'Indications'.)

The role of surgical left atrial appendage occlusion in patients with AF undergoing cardiac surgery is discussed separately. (See "Atrial fibrillation: Left atrial appendage occlusion".)

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

●The choice of mitral valve repair versus mitral valve replacement with chordal sparing differs for patients with chronic primary mitral regurgitation (MR) from that in patients with chronic secondary MR.

•When surgical treatment is indicated for patients with chronic severe primary MR, when successful and durable mitral valve repair is expected, mitral valve repair is preferred to mitral valve replacement. The decision on whether to attempt mitral valve repair is based upon the specific valve lesion and the surgeon’s experience with the specific valve lesion. (See 'Valve repair versus valve replacement' above and "Chronic primary mitral regurgitation: Indications for intervention".)

•For patients with severe secondary (ischemic) MR who are undergoing mitral valve surgery, we suggest concurrent mitral valve replacement with chordal sparing, rather than mitral valve repair (Grade 2B). (See 'Valve repair versus valve replacement' above.)

•For patients with severe secondary (nonischemic) MR who are undergoing mitral valve surgery, we suggest mitral valve replacement with chordal sparing unless valve anatomy is favorable for repair and intraoperative transesophageal echocardiography demonstrates little or no residual MR after repair (Grade 2C). (See 'Valve repair versus valve replacement' above.)

●For patients who require mitral valve replacement, the choice is between a mechanical valve, which requires life-long anticoagulation, and bioprosthetic valve, which does not require anticoagulation but has limited durability, primarily in patients under age 65. (See 'Mechanical versus bioprosthetic valves' above and "Choice of prosthetic heart valve for surgical aortic or mitral valve replacement".)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges William H Gaasch, MD (deceased), who contributed to an earlier version of this topic review.