What is the treatment approach for a patient with moderate mitral regurgitation (MR)?

Treatment of Moderate Mitral Regurgitation

The management of moderate MR depends fundamentally on whether it is primary (degenerative) or secondary (functional), with medical optimization being the cornerstone for secondary MR and watchful waiting for primary MR, while isolated intervention is generally not indicated for moderate severity in either type. 1, 2

Initial Diagnostic Confirmation

Before proceeding with any management strategy, you must verify the MR severity using comprehensive multiparametric echocardiography, not relying on a single measurement 1:

• Measure vena contracta width, effective regurgitant orifice area (EROA), regurgitant volume, and regurgitant fraction 1
• Obtain transesophageal echocardiography (TEE), cardiac magnetic resonance (CMR), or cardiac catheterization when uncertainty exists between mild-to-moderate or moderate-to-severe MR 1
• Distinguish primary from secondary MR as this fundamentally changes your entire management algorithm 1, 2

Management of Moderate Primary (Degenerative) MR

Surgery is NOT indicated for isolated moderate primary MR in asymptomatic patients, even when valve repair feasibility is excellent 1:

• Implement clinical surveillance with echocardiography every 6-12 months to monitor for progression to severe MR 2
• Refer to a multidisciplinary heart team only if the patient develops symptoms attributable to MR 1, 3
• Consider mitral valve repair at the time of coronary artery bypass grafting (CABG) if the patient has multivessel coronary disease requiring revascularization 3

Common pitfall: Do not rush to intervention based on excellent surgical candidacy alone—moderate primary MR does not warrant isolated surgery regardless of repair feasibility 1.

Management of Moderate Secondary (Functional) MR

Guideline-directed medical therapy (GDMT) is mandatory as first-line treatment and must be maximized before considering any intervention 3, 2:

Step 1: Optimize Medical Therapy

Implement the following medications aggressively 3, 2:

• ACE inhibitors or ARBs as first-line neurohormonal antagonists 3, 2
• Beta-blockers to prevent left ventricular deterioration 3, 2
• Mineralocorticoid receptor antagonists (aldosterone antagonists) in the presence of heart failure 3, 2
• Diuretics for fluid overload management 3, 2
• Nitrates for acute dyspnea related to the dynamic component of MR 3

Critical point: The severity of secondary MR is highly dynamic and load-dependent—do not label patients as having severe MR until they are on optimally tolerated doses of GDMT 3. MR severity commonly decreases by 40-45% with optimal medical therapy 4.

Step 2: Implement Cardiac Resynchronization Therapy (CRT)

• Apply CRT in patients meeting guideline criteria (typically LVEF ≤35%, QRS ≥150 ms, left bundle branch block) before considering valve intervention 3, 2
• CRT can immediately reduce MR severity through increased closing force and resynchronization of papillary muscles, with further reduction occurring through decreased tethering force as the left ventricle reverse remodels 3

Step 3: Address Atrial Fibrillation

• Pursue restoration and maintenance of sinus rhythm in patients with atrial fibrillation, as this significantly reduces MR severity 4

Step 4: Consider Revascularization

• Perform coronary revascularization if ischemic cardiomyopathy is present and viability is demonstrated 3

Step 5: Surveillance for Progression

• Monitor for progression to severe secondary MR (EROA ≥0.3-0.4 cm²) 1, 2
• Assess for development of persistent NYHA class II-IV symptoms despite optimal medical therapy 3, 2

When to Consider Intervention for Moderate Secondary MR

Intervention for moderate secondary MR should be considered only in the specific context of concurrent CABG 3:

• Mitral valve repair (preferably with a rigid complete annuloplasty ring) should be considered in patients with moderate secondary MR undergoing CABG 3
• Exercise echocardiography should be performed when feasible—exercise-induced dyspnea with large increases in MR severity and systolic pulmonary artery pressure favor combined surgery 3

Important caveat: There are no data supporting surgical correction of isolated moderate MR without concurrent cardiac surgery 3. Transcatheter edge-to-edge repair (TEER) is indicated only for severe secondary MR (EROA ≥0.3 cm²), not moderate MR 3, 2.

Multidisciplinary Heart Team Evaluation

All intervention decisions must involve heart team discussion, including 3, 1, 2:

• Cardiologist with heart failure expertise (essential for secondary MR) 2
• Cardiac surgeon experienced in mitral valve repair 2
• Assessment of valve morphology, MR etiology, patient comorbidities, and surgical risk 2

Bottom line: For moderate MR, the heart team discussion is warranted only when concurrent cardiac surgery is planned or when symptoms develop despite optimal therapy 1, 2.