When is surgical intervention recommended for patients with moderate to severe mitral regurgitation?

Timing of Surgery for Moderate to Severe Mitral Regurgitation

For primary mitral regurgitation, surgery is indicated immediately when patients develop symptoms with LVEF >30%, or when asymptomatic patients develop LV dysfunction (LVEF ≤60% or LVESD ≥40 mm). 1, 2

Symptomatic Primary Mitral Regurgitation

Surgery is recommended for all symptomatic patients with severe primary MR and LVEF >30%, regardless of the degree of LV dysfunction. 1, 2 This represents a Class I indication across all major guidelines. 1

• Even patients with LVEF between 30-60% should undergo surgery when symptomatic, as this improves survival and prevents irreversible cardiac damage. 1
• For symptomatic patients with LVEF <30%, surgery may still be considered if they remain refractory to medical therapy, but only when there is high likelihood of durable repair and low comorbidity. 2
• Mitral valve repair is strongly preferred over replacement when feasible, particularly for degenerative disease involving the posterior leaflet. 1

Asymptomatic Primary Mitral Regurgitation with LV Dysfunction

Surgery is recommended (Class I) for asymptomatic patients who develop LV dysfunction defined as LVEF ≤60% and/or LVESD ≥40 mm. 1, 2 This threshold represents the critical point where compensatory mechanisms begin to fail and irreversible myocardial damage occurs.

• The LVESD threshold of 40 mm should be adjusted downward (to 22 mm/m² BSA) in patients of small stature. 1
• Both American and European guidelines agree on these exact cutoffs, making this one of the most consistent recommendations across societies. 1
• Early surgery at these thresholds (within 2 months of meeting criteria) is associated with better outcomes than delayed intervention. 1

Asymptomatic Primary Mitral Regurgitation with Preserved LV Function

For asymptomatic patients with LVEF >60% and LVESD <40 mm, surgery should be considered (Class IIa) when specific high-risk features develop:

• New-onset atrial fibrillation warrants surgical consideration. 1, 2
• Pulmonary hypertension (systolic PAP >50 mmHg at rest) is an indication for surgery. 1, 2
• Flail leaflet with LVESD ≥40 mm should prompt surgical evaluation. 1

Surgery may be considered (Class IIb) in highly selected asymptomatic patients with preserved LV function when:

• There is >95% likelihood of successful repair at an experienced center with expected mortality <1%. 2
• Severe LA enlargement (volume index ≥60 mL/m²) is present in sinus rhythm. 1
• Pulmonary hypertension on exercise (systolic PAP ≥60 mmHg) develops. 1

The critical caveat here is that these "early surgery" recommendations only apply at experienced mitral valve centers with high repair rates (>80-90%) and low operative mortality (<1%). 2, 3 Referring patients to such centers is essential, as outcomes are significantly better than at low-volume centers.

Secondary (Functional) Mitral Regurgitation

The approach to secondary MR differs fundamentally because the valve itself is structurally normal and MR reflects underlying ventricular disease. 1

Surgery or intervention for secondary MR should only be considered in symptomatic patients who remain symptomatic despite optimal guideline-directed medical therapy (GDMT), including cardiac resynchronization therapy if indicated. 1, 2

• For patients undergoing CABG with LVEF >30%, concomitant mitral valve surgery is recommended when severe secondary MR is present. 2
• Transcatheter edge-to-edge repair (TEER) should be considered in symptomatic patients with LVEF >30%, appropriate anatomy, and no indication for revascularization after optimal GDMT. 2
• The evidence for isolated surgery in secondary MR is weak, as restoration of valve competence does not address the underlying myocardial disease and survival benefit is uncertain. 1

Transcatheter Options

TEER may be considered as an alternative to surgery only in symptomatic patients with severe primary MR who are at high or prohibitive surgical risk and have favorable anatomy. 1, 2

• For primary MR, TEER is reasonable when LVEF is 20-50%, LVESD ≤70 mm, and PASP ≤70 mmHg. 2
• For secondary MR, TEER should be considered in symptomatic patients meeting COAPT criteria (LVEF >30%, appropriate anatomy) who remain symptomatic after GDMT. 1, 2
• TEER is not a substitute for surgery in low-risk patients, where repair provides superior long-term outcomes. 1

Critical Pitfalls to Avoid

• Do not delay surgery in asymptomatic patients once LVEF drops to 60% or LVESD reaches 40 mm, as even mild symptoms at the time of surgery are associated with worse post-operative cardiac function. 1
• Do not refer patients for "early surgery" unless they are going to an experienced center with documented high repair rates and low mortality, as the risk-benefit calculation changes dramatically at low-volume centers. 2, 3
• Do not use vasodilators (including ACE inhibitors) routinely in chronic primary MR, as there is no evidence they alter disease progression, and they may worsen MR in conditions like mitral valve prolapse. 1, 4
• Do not treat secondary MR with surgery alone without optimizing medical therapy first, including beta-blockers, RAAS inhibitors, and cardiac resynchronization therapy when indicated. 1, 2

Monitoring Strategy

• Asymptomatic severe MR requires follow-up every 6-12 months with echocardiography. 2
• Asymptomatic moderate MR with preserved LV function requires yearly clinical follow-up with echocardiography every 1-2 years. 2
• More frequent reassessment is needed if progressive LV dilation is occurring. 2
• Consider exercise echocardiography, Holter monitoring, and cardiac MRI for risk stratification in borderline cases. 2