Mitral Valve Disease: Regurgitation, Stenosis, and Your Treatment Options.

The mitral valve is the heart's most anatomically complex valve — a sophisticated apparatus comprising two leaflets (anterior and posterior), an annulus (the fibrous ring that supports the leaflets), chordae tendineae (tendon-like cords connecting the leaflets to the papillary muscles), and the papillary muscles themselves (arising from the left ventricular wall). Disease or dysfunction of any component can cause mitral valve failure.

The mitral valve separates the left atrium from the left ventricle. During diastole, it opens to allow blood to flow from the atrium into the ventricle. During systole, it closes to prevent blood from flowing backward into the atrium and lungs. When the valve fails to close properly, mitral regurgitation (MR) results. When the valve fails to open fully, mitral stenosis (MS) results.

Mitral valve disease is the second most common valvular heart disease (after aortic stenosis) and the most common indication for valve surgery in patients under 65. Approximately 2-3% of the general population has some degree of mitral regurgitation, though most cases are mild and do not require intervention.

The most critical distinction in mitral regurgitation is between primary (degenerative) and secondary (functional) MR. This classification fundamentally determines treatment strategy, expected outcomes, and the role of surgery.

Primary (degenerative) MR: The valve itself is abnormal. Causes include:

• Mitral valve prolapse (MVP): The most common cause of primary MR in developed countries. One or both leaflets are redundant and prolapse into the left atrium during systole. Myxomatous degeneration (Barlow's disease) produces thickened, redundant tissue. Fibroelastic deficiency produces thin, translucent leaflets with ruptured chordae.
• Ruptured chordae: Can occur spontaneously in myxomatous disease, or from endocarditis. Produces acute severe MR with flail leaflet segment.
• Infective endocarditis: Vegetations and leaflet destruction.
• Rheumatic disease: Leaflet thickening and restricted motion. More common globally than in the US/Europe.

Secondary (functional) MR: The valve leaflets are structurally normal, but the valve leaks because the left ventricle is dilated and dysfunctional, displacing the papillary muscles and tethering the leaflets. Causes include:

• Ischemic cardiomyopathy (coronary artery disease with prior MI causing regional wall motion abnormalities)
• Non-ischemic dilated cardiomyopathy
• Atrial functional MR (annular dilation from chronic atrial fibrillation)

This distinction matters enormously because the evidence base for treatment differs dramatically. Surgery for primary MR (especially repair) has excellent long-term outcomes. Surgery for secondary MR is more controversial — the CTSN trials showed that while repair or replacement can reduce regurgitation, it does not consistently improve survival because the underlying ventricular disease persists.

Accurate grading of MR severity is essential because treatment recommendations are driven by severity classification. Unfortunately, MR grading is one of the most challenging assessments in echocardiography, and inter-observer variability is significant.

Echocardiographic grading (ACC/AHA stages):

• Stage A (At Risk): MVP without MR, or mild annular dilation. No treatment needed; periodic surveillance.
• Stage B (Progressive): Mild-to-moderate MR. Regurgitant volume <60 mL, EROA <0.40 cm², vena contracta <0.7 cm. Annual echocardiography.
• Stage C (Asymptomatic Severe): Severe MR without symptoms. Regurgitant volume ≥60 mL, EROA ≥0.40 cm², vena contracta ≥0.7 cm. This is the "watchful waiting" stage — intervention timing is debated.
• Stage D (Symptomatic Severe): Severe MR with symptoms (dyspnea, exercise intolerance, atrial fibrillation, pulmonary hypertension). Intervention indicated (Class I).

Key diagnostic modalities:

• Transthoracic echo (TTE): First-line test. Assesses severity, mechanism, leaflet morphology, LV size and function, LA size, pulmonary artery pressure.
• Transesophageal echo (TEE): Superior visualization of mitral anatomy. Essential for surgical planning — identifies specific leaflet segments involved (Carpentier classification: A1-A3 for anterior leaflet, P1-P3 for posterior). Required before MitraClip to assess suitability.
• Cardiac MRI: Increasingly used as a referee when echo-based severity grading is uncertain. Provides highly accurate regurgitant volume quantification. The MRIR trial demonstrated that CMR-based MR quantification reclassified severity in 30% of patients compared to echo alone.
• Exercise echocardiography: Valuable in patients with borderline symptoms — can unmask exercise-induced increases in MR severity and pulmonary pressure that are not present at rest.

For primary degenerative mitral regurgitation, repair is superior to replacement and is the preferred intervention when performed by an experienced surgeon. The ACC/AHA guidelines give a Class I recommendation for mitral valve repair over replacement for primary MR when a durable repair is likely.

Why repair is preferred:

• Lower operative mortality (0.5-1.0% vs 3-5% for replacement)
• Preservation of the native valve apparatus and left ventricular geometry
• No need for long-term anticoagulation
• Superior long-term survival compared to replacement (multiple observational studies)
• Lower risk of endocarditis compared to prosthetic valves

Repair techniques:

• Leaflet resection: Triangular or quadrangular resection of prolapsing posterior leaflet segments. The classical Carpentier technique.
• Neochordae (artificial chordae): Gore-Tex (ePTFE) sutures replace ruptured or elongated chordae, supporting the prolapsing segment. The "respect rather than resect" philosophy — preserving leaflet tissue.
• Annuloplasty ring: A prosthetic ring (rigid, semi-rigid, or flexible) is sewn to the annulus to restore its normal size and shape. This is a component of virtually all repairs — it stabilizes the repair and prevents future annular dilation.
• Sliding plasty: For Barlow's disease with excessive posterior leaflet height, the leaflet is detached, shortened, and reattached.
• Edge-to-edge (Alfieri stitch): Suturing the middle of the anterior and posterior leaflets together to create a double-orifice valve. Simple but effective for selected patients.

The surgeon repair rate is the single most important variable: At reference centers with fellowship-trained mitral valve specialists, repair rates for degenerative MR exceed 95%, and operative mortality is below 0.5%. The average US repair rate is approximately 65-70%. This means that at some centers, a third of patients who could have been repaired receive a replacement instead. The gap is consequential — replacement carries higher mortality, requires anticoagulation (if mechanical), and has inferior long-term outcomes.

ACC/AHA guidelines recommend referral to a "Heart Valve Center of Excellence" — defined as centers with high repair rates (>95% for posterior leaflet prolapse), low operative mortality (<1%), and high annual mitral surgery volume (>25 cases/year).

Mitral valve replacement is appropriate when repair is not feasible — typically in cases of severe rheumatic disease with extensive leaflet destruction, heavily calcified annulus, or certain secondary MR patterns. The valve choice (mechanical vs bioprosthetic) involves similar tradeoffs as in aortic valve replacement, with some mitral-specific considerations.

Mechanical mitral valves:

• Require lifelong anticoagulation with warfarin (target INR 2.5-3.5 for mitral position — higher than aortic position due to lower flow velocity)
• Annual major bleeding risk: 1.5-3.0%
• Superior durability — essentially unlimited lifespan
• Preferred for patients under 50 who can comply with anticoagulation

Bioprosthetic mitral valves:

• No long-term anticoagulation needed (short-term warfarin for 3 months, then aspirin alone)
• Degenerate faster in the mitral position than the aortic position due to higher closing pressures
• Expected lifespan: 10-15 years (shorter than aortic bioprostheses)
• Transcatheter mitral valve-in-valve replacement is an emerging option for failed bioprosthetic valves, though more technically challenging than aortic valve-in-valve

Critical surgical principle: When replacing the mitral valve, preservation of the subvalvular apparatus (chordae and papillary muscles) is essential. Chordal-sparing replacement maintains LV geometry and function. Older techniques that excised the subvalvular apparatus resulted in poorer ventricular function and higher mortality.

Mitral stenosis: Pure mitral stenosis is almost exclusively caused by rheumatic heart disease. Treatment depends on severity and valve anatomy. Percutaneous mitral balloon commissurotomy (PMBC) is the preferred intervention for favorable valve morphology (Wilkins score ≤8), with success rates >90% and low complication rates. When valve anatomy is unfavorable (heavily calcified, significant subvalvular disease, more than mild MR), surgical commissurotomy or replacement is needed.

Transcatheter mitral valve interventions represent one of the fastest-growing areas in structural heart disease. The Abbott MitraClip (now in its fourth generation, MitraClip G4) is the most established device, with over 200,000 implants worldwide.

How MitraClip works: Via femoral venous access and transseptal puncture, a clip device is guided to the mitral valve under TEE and fluoroscopic guidance. The clip grasps the anterior and posterior leaflets, creating a tissue bridge that reduces regurgitation — essentially a percutaneous version of the Alfieri edge-to-edge repair. Multiple clips can be deployed.

Evidence for MitraClip:

• EVEREST II (2011): First randomized trial of MitraClip vs surgery for primary MR. MitraClip was less effective at reducing MR but had fewer major adverse events. More MitraClip patients required mitral surgery within 5 years.
• COAPT (2018): Landmark trial for secondary (functional) MR. In patients with heart failure and persistent moderate-to-severe or severe secondary MR despite optimal medical therapy, MitraClip reduced heart failure hospitalizations by 47% and all-cause mortality by 38% at 2 years. This trial transformed the treatment of secondary MR.
• MITRA-FR (2018): A contemporaneous French trial of MitraClip for secondary MR that showed NO benefit. The discrepancy with COAPT is attributed to patient selection differences — MITRA-FR enrolled patients with more severely dilated ventricles and proportionally less severe MR.

The COAPT vs MITRA-FR reconciliation: The concept of "proportionate" vs "disproportionate" MR has emerged. When MR is disproportionate to ventricular dilation (the valve leak is worse than expected for the degree of heart failure), MitraClip provides dramatic benefit. When MR is proportionate (the leak is an expected consequence of a severely dilated heart), treating the MR alone does not improve outcomes — the ventricle is the primary problem.

Emerging transcatheter mitral technologies:

• Transcatheter mitral valve replacement (TMVR): Multiple devices in clinical trials (Edwards SAPIEN M3, Medtronic Intrepid, Abbott Tendyne). TMVR aims to treat patients who are not candidates for repair or MitraClip. The field is advancing but faces anatomic challenges (larger annulus, LVOT obstruction risk, device anchoring).
• Transcatheter annuloplasty: Devices that reduce annular dimension percutaneously (Cardioband, Millipede). Can be combined with MitraClip for a more complete repair.

Timing of mitral valve intervention is one of the most debated topics in valvular heart disease. Too early, and the patient undergoes an unnecessary operation. Too late, and irreversible ventricular dysfunction may develop. The guidelines attempt to thread this needle.

ACC/AHA 2020 guideline indications for mitral intervention in chronic primary MR:

• Class I (should be done): Symptomatic severe primary MR (Stage D). Also: asymptomatic severe MR with LV dysfunction (EF 30-60% or LVESD ≥40 mm).
• Class IIa (reasonable): Asymptomatic severe primary MR with preserved LV function (EF >60%, LVESD <40 mm) when performed at a Heart Valve Center of Excellence with an expected repair rate >95% and mortality <1%. This is the "early surgery" indication — based on evidence that waiting for symptoms or LV dysfunction leads to worse outcomes because silent myocardial damage accumulates.
• Class IIa (reasonable): Asymptomatic severe MR with new-onset atrial fibrillation or progressive pulmonary hypertension (PASP >50 mmHg at rest).

For secondary MR: The pathway is different. First-line treatment is guideline-directed medical therapy (GDMT) for heart failure: ACE inhibitor/ARB/ARNI, beta-blocker, mineralocorticoid receptor antagonist, SGLT2 inhibitor, and CRT if indicated. Only when severe MR persists despite optimized GDMT should intervention be considered — and the choice between surgery and MitraClip depends on patient-specific factors, surgical risk, and the proportionality of MR to ventricular dilation.

The emerging concept of "early repair" for primary MR is supported by observational data from high-volume centers showing that patients who undergo repair before symptom onset or LV dysfunction have survival equivalent to the age-matched general population. The randomized EARLY trial is currently enrolling to test this approach definitively.

Mitral valve disease is arguably the area of cardiac surgery where surgeon expertise matters most. The difference between a repair rate of 65% and 99% is the difference between a patient keeping their native valve — with all the associated benefits — and receiving a prosthesis with its inherent limitations.

Scenarios where a second opinion is particularly valuable:

• You have been told you need mitral valve replacement: In most cases of degenerative MR, repair is possible in the right hands. If replacement has been recommended without a clear anatomic reason why repair is not feasible, seek a second opinion from a mitral valve specialist.
• You have moderate MR and your cardiologist is "watching it": Serial monitoring is appropriate, but the triggers for intervention should be clearly defined. A second opinion can establish surveillance parameters and identify early indicators of decompensation.
• You have secondary MR and heart failure: The COAPT and MITRA-FR data have created a nuanced clinical landscape. Is your MR proportionate or disproportionate? Would MitraClip help, or would it be futile? These questions require Heart Team evaluation.
• You have been offered MitraClip but are unsure if surgery might be better: MitraClip is less effective at reducing MR than surgical repair. For patients who can tolerate surgery, an open repair at an expert center may provide better durability. But for high-risk patients, MitraClip may be the superior risk-adjusted option.

WhiteGloveMD provides fellowship-trained Heart Team review of mitral valve cases, including independent echo interpretation, surgical repairability assessment, and guideline-based recommendations. Our cardiac surgeons specialize in complex valve repair, and our cardiologists bring expertise in transcatheter mitral therapies. Request your review or view pricing.