Mitral Regurgitation: An Evidence-Based Approach

Background

Mitral regurgitation (MR) is the retrograde flow of blood from the left ventricle into the left atrium during systole due to incompetent closure of the mitral valve. This volume overload increases left atrial and pulmonary pressures, eventually leading to left ventricular dilation, atrial fibrillation, pulmonary hypertension, and heart failure if untreated.

Classification / Types

By Etiology:

• Primary (Degenerative) MR: intrinsic valve disease (e.g., myxomatous degeneration, mitral valve prolapse, rheumatic disease, endocarditis).
• Secondary (Functional) MR: result of LV dilation or papillary muscle dysfunction, seen in ischemic or dilated cardiomyopathy.

By Onset:

• Acute MR: sudden onset, often due to papillary muscle rupture (MI), endocarditis, or trauma.
• Chronic MR: progressive valve degeneration or functional remodeling over time.

By Severity (based on echocardiographic criteria):

• Mild
• Moderate
• Severe (quantified using regurgitant volume, effective regurgitant orifice area, and vena contracta width)

Epidemiology

• Sex: myxomatous degeneration more common in women; ischemic MR more common in men.
• Age: prevalence increases with age due to degenerative changes.
• Geography: degenerative MR more common in high-income countries; rheumatic MR in low- and middle-income countries.
• Comorbidities: often associated with hypertension, coronary artery disease, or heart failure.

Pathophysiology

Incompetent leaflet coaptation allows LV blood to regurgitate into the low-pressure left atrium during systole. In chronic MR, the LV dilates eccentrically to accommodate the volume load, masking systolic dysfunction until late. Acute MR produces a non-compliant LA, rapid pressure transmission, pulmonary edema, and often cardiogenic shock.

Etiology

Causes

• Myxomatous valve degeneration (e.g., mitral valve prolapse)
• Rheumatic heart disease
• Infective endocarditis
• Ischemic heart disease (papillary muscle rupture / dysfunction)
• Cardiomyopathy (dilated or hypertrophic)
• Congenital anomalies (e.g., cleft mitral valve)
• Mitral annular calcification
• Chest trauma or radiation

Risk Factors

• Age >60 years
• Coronary artery disease or prior MI
• Rheumatic fever history
• Connective tissue disorders (e.g., Marfan, Ehlers-Danlos)
• Atrial fibrillation
• Endocarditis

Clinical Presentation

History (Symptoms)

• Fatigue and reduced exercise tolerance
• Dyspnea on exertion, orthopnea, PND
• Palpitations (especially with atrial fibrillation)
• Signs of heart failure in advanced disease
• Acute MR: sudden onset dyspnea, pulmonary edema, hypotension

Physical Exam (Signs)

Vital Signs:

• Tachycardia
• Hypotension (in acute MR)

Cardiac Exam:

• Holosystolic murmur best heard at the apex, radiating to the axilla
• S3 gallop (suggests volume overload)
• Displaced hyperdynamic apical impulse (chronic severe MR)

Pulmonary:

• Rales or crackles with pulmonary edema
• Possible signs of pulmonary hypertension in chronic MR

Peripheral:

• Peripheral edema (in right-sided heart failure)
• Elevated JVP (advanced disease)

Differential Diagnosis

• Mitral stenosis
• Aortic regurgitation
• Tricuspid regurgitation
• Heart failure with preserved / reduced EF
• Cardiomyopathy (dilated, hypertrophic)
• Atrial septal defect
• Constrictive pericarditis

Diagnostic Testing

Initial Tests

• Transthoracic Echocardiogram (TTE): confirms MR severity; assesses valve morphology, regurgitant volume, LV function; measures LA and LV size.
• Transesophageal Echocardiogram (TEE): superior for valve visualization, especially in endocarditis or surgical planning.
• Electrocardiogram (ECG): atrial fibrillation, LA enlargement, or LV hypertrophy.
• Chest X-ray: left atrial and ventricular enlargement; pulmonary vascular congestion.
• BNP / NT-proBNP: elevated in decompensated MR with heart failure.
• Cardiac MRI: precise quantification of regurgitant volume and chamber size.
• Cardiac catheterization: coronary anatomy pre-surgery; assess hemodynamics in unclear cases.

Treatment

Medical Management

Heart failure management:

• Diuretics for volume overload
• Afterload reducers (ACE inhibitors, ARBs) in functional MR
• Beta-blockers in chronic MR with LV dysfunction

Rate control and anticoagulation:

• Beta-blockers, calcium channel blockers, or digoxin for atrial fibrillation
• Anticoagulation (warfarin) in atrial fibrillation, prior embolism, or left atrial thrombus

Endocarditis prophylaxis: not routine unless prior endocarditis or prosthetic valve.

Interventional / Surgical

• Surgical Mitral Valve Repair or Replacement: severe symptomatic MR; asymptomatic severe MR with LV EF ≤60% or LV end-systolic dimension >40 mm. Valve repair is preferred over replacement when feasible.
• Transcatheter Mitral Valve Repair (e.g., MitraClip): select high-risk surgical patients with severe symptomatic MR; more commonly used in functional MR.

Consults

• Cardiology: all moderate to severe MR or symptomatic patients.
• Cardiothoracic Surgery: evaluation for mitral valve surgery.
• Interventional Cardiology: for transcatheter interventions.
• Electrophysiology: recurrent or symptomatic atrial fibrillation.
• Infectious Disease: if endocarditis is suspected.
• Primary Care / Internal Medicine: chronic disease optimization.

Patient Education, Screening, Vaccines

• Importance of adherence to medications and follow-up
• Monitor for worsening heart failure (e.g., dyspnea, edema)
• Weight tracking to detect fluid retention
• Limit sodium intake if volume overload is present
• Avoid excessive physical exertion in symptomatic patients

Vaccinations: influenza annually, pneumococcal, COVID-19.

Follow-Up

• Regular TTE: annually for asymptomatic severe MR; every 6–12 months if LV size/function changes.
• Monitor for development of atrial fibrillation.
• Assess progression of symptoms and candidacy for intervention.
• Optimize management of comorbid conditions (hypertension, CAD).
• Reinforce education on warning signs and when to seek care.

Published in HMD MedDigest — Substance Over Noise. Written for working physicians, by working physicians.