mitral stenosis (MS)

Introduction

Mitral stenosis (MS) impedes blood flow from the lungs & left atrium into the left ventricle.

Classification

• mild
  • mitral valve area > 1.5 cm2
  • mean pressure gradient < 5 mm Hg
  • pulmonary artery systolic pressure < 30 mm Hg
• moderate
  • mitral valve area 1.0-1.5 cm2
  • mean pressure gradient 5-10 mm Hg
  • pulmonary artery systolic pressure 30-50 mm Hg
• severe
  • mitral valve area < 1.0 cm2
  • mean pressure gradient >10 mm Hg
  • pulmonary artery systolic pressure > 50 mm Hg

Etiology

• rheumatic heart disease (most common, almost always)
  • thickening & fusion of mitral valve leaflets
  • generally presents 20-40 years after rheumatic fever
• Ca+2 deposition in mitral annulus & leaflets
• congenital valvular malformation
• association with connective tissue disorders
• prosthetic valves (especially bioprosthetic valves) may become stenotic

Pathology

• Elevation of left atrial pressure
• Elevation of pulmonary venous pressure
• Elevation of pulmonary capillary pressure
• pulmonary congestion
• pressure elevation depends upon the pressure gradient across the valve which in turn depends upon:
  • severity of obstruction
  • flow across the mitral valve
  • time allowed for diastolic filling of left ventricle
  • presence of an effective atrial contraction
• factors increasing flow across stenotic mitral valve may cause a marked increase in left atrial pressure & exacerbate heart failure
  • tachycardia
  • exercise
  • fever
• pregnancy
• Left atrial enlargement & atrial fibrillation
  • may result in atrial thrombus formation
  • high incidence of systemic embolization in patients with mitral stenosis who are not anticoagulated (20%)
• right ventricular hypertrophy is a late manifestation

Clinical manifestations

• symptoms do not develop for several years after signs of mitral stenosis are detectable on physical examination
• signs
  • variable S1
  • accentuation of P2 suggests pulmonary hypertension
  • early diastolic opening snap (opening snap after S2) if leaflets are mobile
    • interval between S2 & opening snap is short with severe mitral stenosis
    • described as high-pitched sound after S2
  • rumbling, low-pitched apical diastolic murmur (decrescendo)
    • the longer the murmur, the more severe the stenosis
    • intensity of the murmur correlates with transvalvular pressure gradient
    • best heard at apex in the left lateral decubitus position
    • no radiation of murmur
  • prominent jugular venous a wave
  • prominent tapping apical impulse
  • right heart failure
• symptoms
  • fatigue & dyspnea on exertion
  • pulmonary congestion
  • orthopnea & paroxysmal nocturnal dyspnea
  • atrial fibrillation causes significant exacerbation of symptoms
  • diffuse alveolar hemorrhage may occur

Diagnostic procedures

• electrocardiogram
  • notched P wave, duration > 0.12 sec in ECG lead II
  • right ventricular hypertrophy
  • left atrial enlargement
• echocardiography*
  • confirm mitral stenosis
  • access chamber size & function
  • detect left atrial thrombus
  • assess pulmonary artery pressure
  • trans-esophageal echocardiogram
    • to evaluate thromboembolism (left atrial appendage thrombus)
    • better defines valvular anatomy
  • mean gradient:
    • < 6 mm Hg: mild
    • 6-11 mm Hg: moderate
    • >= 12 mm Hg: severe
  • mitral valve area
    • 1.5-2 cm2: mild
    • 1-1.5 cm2: moderate
• < 1 cm2: severe
  • frequency of serial evaluation
    • every 3-5 years for mild MS
    • every 1-2 years for moderate MS
    • every year for severe MS
• exercise echocardiography
  • disparate findings of symptoms vs resting echocardiogram
• cardiac catheterization
  • concomitant coronary artery disease
  • suboptimal or nondiagnostic echocardiogram
  • other suspected valvular lesions such as mitral regurgitation

* video

Radiology

• chest x-ray
  • enlargement of pulmonary artery, right ventricle, right atrium, left atrium
  • straightening of left heart border
  • large left atrial shadow
  • dilated upper lobe pulmonary veins
  • Kerley B lines may be present with severe stenosis

Complications

• atrial fibrillation & pulmonary edema

• disease interaction(s) of atrial fibrillation with mitral stenosis

Differential diagnosis

• left atrial myxoma
  • fevers, progressive dyspnea
• mitral valve endocarditis associated with mitral regurgitation
• marantic endocarditis not associated with cardiac murmur
• cor triatriatum

Management

• avoid &/or treat factors which elevate left atrial pressure
  • vigorous physical activity
  • fever
  • tachycardia
  • pregnancy: repair indicated prior to conception
• diuretics & long-acting nitrates for pulmonary congestion & edema
• beta-blocker or calcium channel blocker for sinus tachycardia allows greater time for ventricular filling
• co-existent atrial fibrillation
  • high risk of thromboembolic events
  • anticoagulation indicated
    • heparin at onset
    • long-term warfarin
      • direct oral anticoagulant should not be used for patients with rheumatic mitral stenosis
  • pharmacologic control of ventricular rate
    • digoxin
    • verapamil 5-10 mg IV, then 80 mg PO TID
    • beta-blocker
  • cardioversion
    • synchronized DC cardioversion if hemodynamically compromised
      • hypotension
      • pulmonary edema
      • angina
    • attempt to restore sinus rhythm indicated except in presence of marked left atrial enlargement
    • elective attempts at chemical cardioversion or electrical cardioversion should be preceded by anticoagulation for 3 weeks to minimize risk of thromboembolic event after restoration of sinus rhythm
    • chemical cardioversion with type Ia anti-arrhythmic agent
      • quinidine
      • procainamide
    • synchronized DC cardioversion if chemical cardioversion fails
    • continue type Ia anti-arrhythmic agent after successful cardioversion to maintain sinus rhythm
  • radiofrequency ablation if mitral valve surgery
• long-term anticoagulation, target INR 2-3
  • history of prior thromboembolism
  • paroxysmal atrial fibrillation or chronic atrial fibrillation
  • left atrial diameter > 5.5 cm
  • left atrial thrombus
• prophylaxis for infective endocarditis
  • no longer routinely indicated
• continuous prophylaxis against rheumatic fever
  • young patients
  • patients at high risk for Streptococcal infection
    • parents of young children
    • school teachers
    • medical personnel
    • military personnel
    • patients living in crowded conditions
  • patients with acute rheumatic fever within 5 years
• surgery
  • procedures
    • percutaneous balloon mitral commissurotomy
      • see percutaneous balloon mitral valvuloplasty (below)
    • mitral valve replacement (MVR)
      • operative mortality high in elderly (5-15%)
  • indications
    • symptoms, NYHA functional class 3 or 4
    • pulmonary hypertension
      • pulmonary artery systolic pressure > 50 mm Hg at rest or > 60 mm Hg with exercise
    • mitral valve area < 1 cm2/m2 (body surface area)
    • recurrent systemic thromboembolism (not mentioned in MKSAP17)
    • severe mitral stenosis in patients undergoing cardiac surgery for other reasons
    • pregnancy if percutaneous balloon mitral valvuloplasty not feasible
    • also see percutaneous balloon mitral valvuloplasty
• percutaneous balloon mitral valvuloplasty (commissurotomy)
  • favorable valve morphology
    • patients at high risk for surgery
    • young age without contraindications
  • indications
    • symptomatic
    • mitral valve area < 1.5 cm2
    • pliable, non-calcified leaflets
    • pulmonary artery pressure > 50 mm Hg at rest or > 60 mm Hg with exercise
    • pregnancy or planned pregnancy in patients with severe mitral stenosis, regardless of symptoms
      • mitral valve balloon angioplasty for most patients
  • contraindications
    • significant (> mild) mitral regurgitation
    • calcified mitral valve
      • most elderly are not candidates
    • atrial thrombus
    • recent thromboembolic events

Follow-up (asymptomatic mitral stenosis)

• clinical evaluation yearly
• echocardiogram to assess aortic valve area
  • yearly for severe MS
  • every 1-2 years for moderate MS
  • every 3-5 years for mild MS

Additional terms

• mitral regurgitation (MR)
• mitral valve