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MITRAL REGURGITATION (MR) - Complete Exam Notes

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DEFINITION

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ETIOLOGY (Box 1.36)

Key Concept:

1. Valve leaflets
2. The annulus
3. The chordae tendineae
4. Papillary muscles
5. The left ventricle

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Causes of ACUTE Mitral Regurgitation:

• Infective endocarditis (IE) - most important
• Rupture of a papillary muscle - e.g., in acute myocardial infarction (AMI) or mitral valve prolapse
• Chest trauma
• Cardiac surgery
• Acute rheumatic carditis
• Dysfunction of prosthetic valve

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Causes of CHRONIC Mitral Regurgitation (by structure damaged):

Causes by Clinical Setting:

• MR in IE: Leaflet perforation, vegetations preventing leaflet function, rupture of chordae tendineae, annular abscess
• MR in RHD: Rigid and retracted leaflets, shortening of chordae tendineae
• MR in CAD: Regional wall motion abnormalities, ischemia of papillary muscle, LV failure

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PATHOPHYSIOLOGY

Acute Mitral Regurgitation:

• The left atrium has normal compliance - it cannot dilate much acutely
• Sudden regurgitation causes a sharp rise in left atrial pressure and pulmonary venous pressure
• This leads to acute pulmonary edema
• Stroke volume increases (less than in chronic) to maintain forward cardiac output
• May result in some LV enlargement

Chronic Mitral Regurgitation:

• Gradual regurgitation leads to slow dilatation of left atrium
• The enlarged LA accommodates regurgitant flow with little increase in left atrial pressure initially
• In longstanding cases, the left ventricle slowly dilates due to chronic volume overload
• LV diastolic and left atrial pressures gradually increase
• "MR begets MR" - as LV dilates, the annulus dilates further, worsening regurgitation

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CLINICAL FEATURES

SYMPTOMS

• Usually presents with dyspnea due to acute pulmonary edema

• May be asymptomatic for many years
• Becomes symptomatic only after onset of irreversible LV dysfunction
• Symptoms include:

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SIGNS

Pulse:

• Volume is HIGH (due to increased stroke volume)
• In severe MR: may be mildly collapsing
• Irregular rhythm and varying volume if atrial fibrillation is present
• Pulsus alternans in acute MR

Jugular Venous Pressure (JVP):

Blood Pressure:

• In severe MR: wide pulse pressure
• Three recordings needed if patient has AF

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INSPECTION AND PALPATION

• Hyperdynamic precordium
• Apex beat:
  • Shifted to the LEFT (due to LV dilatation)
  • Forceful - feels active and rocking
  • Diffuse (hyperdynamic) in character due to LV volume overload
• Cardiomegaly: Present in chronic MR. Acute MR does NOT produce cardiomegaly
• Systolic thrill at apex (if MR is severe)
• Left parasternal heave and palpable P2
• Epigastric pulsations of right ventricular type

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AUSCULTATION

Heart Sounds:

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MURMUR OF MITRAL REGURGITATION

Typical Apical Pansystolic Murmur - Features:

• High-pitched, blowing quality
• Holosystolic/pansystolic - loudest at the apex
• Plateau-shaped (uniform intensity throughout systole)
• Best heard with the diaphragm of the stethoscope
• Radiation:
  • Into axilla and left interscapular area if anterior leaflets involved (as in rheumatic)
  • To base if posterior leaflets involved
• Produced by the mitral regurgitant jet occurring throughout the whole of systole
• May be accompanied by a thrill

Character of Murmur Depending on Pathology (Table 1.68):

Severe MR with Soft or No Murmur (Silent MR):

• Left ventricular dilation
• Acute MR
• Paraprosthetic MR
• COPD, obesity
• Dampened MR

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DYNAMIC AUSCULTATION

• Non-MVP MR murmur vs MVP murmur:
  • Non-MVP MR murmur: Increases with squatting, decreases with standing
  • MVP murmur: Opposite - decreases with squatting, increases with standing
• MR murmur vs AS/HCM murmur:
  • MR murmur: Increases with isometric handgrip
  • AS/HCM: Opposite - decreases with isometric handgrip

Other Murmurs in MR:

• Short mid-diastolic flow murmur: Rumbling, at apex in severe cases - due to increased flow across mitral valve; may follow S3
• Ejection systolic murmur or early diastolic murmur at pulmonary area when pulmonary hypertension is present
• Pansystolic murmur at lower left sternal border when functional tricuspid regurgitation is present
• Opening snap can be heard in 10% of patients with MR

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SIGNS INDICATING SEVERITY OF MR (Box 1.37)

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SIGNS IN ACUTE MITRAL REGURGITATION

• Normal apical impulse (no ventricular dilatation yet)
• Third and/or fourth heart sound
• An early systolic or pansystolic murmur

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DIFFERENCES: ACUTE vs CHRONIC MR (Table 1.69)

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DIFFERENCES: MVP-MR vs Rheumatic Heart Disease-MR (Table 1.70)

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INVESTIGATIONS

Electrocardiogram (ECG):

• Enlargement/hypertrophy of left atrium (if not in AF)
• Dilatation and hypertrophy of left ventricle
• Hypertrophy of both left and right ventricle in pulmonary hypertension
• Atrial fibrillation

Chest X-ray:

• Enlargement of the left atrium (more than in MS) and the left ventricle
• Pulmonary venous congestion
• Pulmonary edema - interstitial edema in acute MR, chronic decompensated MR, or with coexistent MS
• Annular calcium appears as a C-shaped opacity in posterior third of heart in lateral or RAO (right anterior oblique) view

Echocardiogram:

• Shows dilated left atrium and left ventricle
• Identifies structural abnormalities of mitral valve (prolapse, chordal, or papillary muscle ruptures)
• Doppler echo: Detects and quantifies severity of regurgitation; detects mitral annular calcification
• Transesophageal Echocardiography (TEE):
  • Useful to identify structural valve abnormalities
  • Helpful before surgery, especially in MVP
  • Intraoperative TEE assesses efficacy of valve repair
  • MVP defined as >2 mm systolic displacement of mitral leaflet into the LA

Cardiac Catheterization:

• Shows dilated left atrium and left ventricle
• Mitral regurgitation and pulmonary hypertension
• Coexisting coronary artery disease (if present)

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COMPLICATIONS (Box 1.38)

• Progressive heart failure - most common cause of death
• Less frequent: Sudden death, stroke, fatal endocarditis
• Atrial fibrillation
• Infective endocarditis
• Left ventricular failure
• Pulmonary hypertension (late) and right ventricular failure (very late)
• Rarely: Systemic embolism

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MANAGEMENT

Conservative:

• Asymptomatic mild MR can be managed conservatively

Medical Management:

• Acute MR: Afterload reduction with nitroprusside
• Chronic MR:
  • High afterload worsens regurgitation, so vasodilators are used (ACE inhibitors, nifedipine)
  • Diuretics
  • Treatment of AF: Digoxin and anticoagulants
  • Anticoagulation
  • Infective endocarditis prophylaxis
  • Rheumatic fever prophylaxis

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Surgical Management - Flowchart 1.6:

Chronic Severe MR:

• Echocardiography first
  • If EF >0.60 AND end-systolic dimension <45 mm:
    • No AF or pulmonary hypertension → Clinical and echocardiographic follow-up
    • AF or pulmonary hypertension → Mitral valve surgery (repair preferred)
  • If EF ≤0.60 OR end-systolic dimension ≥45 mm:
    • Mitral valve surgery (repair preferred)

• Echocardiography
  • Mitral valve reparable → Mitral valve surgery (repair preferred)
  • Mitral valve not reparable:
    • EF ≥0.30 → Mitral valve replacement
    • EF <0.30 → Medical therapy

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ESC Guidelines for Surgical Intervention (Table 1.71):

Conditions where Mitral Valve REPAIR is Possible (Box 1.39):

• Mitral valve prolapse (MVP)
• Papillary muscle dysfunction
• Leaflet perforation due to IE
• Chordal rupture
• Annular dilation
• Rheumatic MR in the young

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COMBINED MITRAL STENOSIS AND MITRAL REGURGITATION (Table 1.72)

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QUICK EXAM MEMORY AID

• Holosystolic
• Apical, loudest
• Pansystolic
• Plateau-shaped
• Radiates to axilla