Key Facts

Mitral stenosis (MS) is narrowing of the mitral valve orifice that impedes diastolic blood flow from the left atrium to the left ventricle. It is almost exclusively caused by rheumatic heart disease.

Epidemiology

• Declining incidence in developed countries; still prevalent in developing nations
• Rheumatic MS: predominantly affects women (F:M ~2:1)
• Symptoms typically develop 20-40 years after rheumatic fever episode
• Prevalence in UK: ~1-2 per 1,000 adults (mostly immigrant populations)

Aetiology

• Rheumatic heart disease: >95% of cases; commissural fusion, leaflet thickening, chordal shortening
• Degenerative (mitral annular calcification): elderly, CKD, dialysis patients
• Congenital: rare (parachute mitral valve, cor triatriatum)
• SLE (Libman-Sacks endocarditis)
• Carcinoid syndrome (rare)
• Mucopolysaccharidoses

Pathophysiology

• Narrowed mitral orifice creates a pressure gradient between LA and LV during diastole
• LA pressure rises → LA dilatation → pulmonary venous congestion → pulmonary hypertension
• Pulmonary hypertension leads to RV pressure overload → RV dilatation and failure
• LV is relatively 'protected' — LV function often preserved
• AF develops from LA dilatation → loss of atrial contraction → thrombus formation → stroke risk

Typical Presentation

• Dyspnoea: exertional initially, progressing to orthopnoea and PND
• Palpitations: often from AF
• Haemoptysis: pulmonary venous congestion, rupture of bronchial veins
• Thromboembolism: stroke or peripheral embolism (especially with AF)
• Fatigue: low cardiac output
• Symptoms worsen with increased HR: exercise, pregnancy, fever, AF with fast ventricular rate

Examination Findings

• Malar flush (mitral facies): dusky purple cheek discolouration
• Low-pitched mid-diastolic rumble at apex (best with bell in left lateral decubitus)
• Opening snap (OS): heard after S2; short S2-OS interval = more severe
• Loud S1 (pliable valve snapping shut)
• Tapping, non-displaced apex beat (palpable S1)
• Signs of pulmonary hypertension: loud P2, RV heave, elevated JVP, peripheral oedema

Red Flags

• Acute pulmonary oedema (especially in pregnancy or new-onset AF)
• Stroke or systemic embolism
• Severe pulmonary hypertension
• Right heart failure (ascites, hepatomegaly, peripheral oedema)

Bedside

• ECG: P mitrale (bifid P waves, LA enlargement), AF, RVH (if pulmonary hypertension)
• CXR: LA enlargement (double heart border, splayed carina), pulmonary congestion, Kerley B lines, mitral valve calcification

Bloods

• BNP/NT-proBNP: elevated with heart failure
• FBC: polycythaemia (chronic hypoxia)
• Anti-streptolysin O titre (ASOT): historical rheumatic fever
• TFTs, U&Es: preoperative

Imaging

• Transthoracic echocardiography: valve area (planimetry, PHT method), mean gradient, LA size, pulmonary artery pressure, RV function
• TOE: better valve morphology assessment, exclude LA thrombus pre-intervention
• Cardiac catheterisation: confirm haemodynamics if echo equivocal; coronary assessment pre-surgery

Special Tests

• Wilkins score: echocardiographic assessment of valve suitability for balloon valvuloplasty (leaflet mobility, thickening, calcification, subvalvular disease; score 0-16; ≤8 favourable for PMBV)
• Exercise echocardiography: assess gradient and pulmonary pressures with exercise if symptomatic with moderate MS

Non-pharmacological

• Avoid precipitants: treat fever promptly, avoid excessive salt/fluid
• Pregnancy counselling: MS poorly tolerated in pregnancy (increased blood volume, tachycardia)

Pharmacological

• Rate control in AF: beta-blockers (bisoprolol 2.5-10mg OD) or rate-limiting CCBs (diltiazem) to prolong diastolic filling time
• Anticoagulation: warfarin (not DOACs) for AF, prior embolism, or LA thrombus (NICE NG208)
• Diuretics: for pulmonary congestion
• Rheumatic fever prophylaxis: phenoxymethylpenicillin 250mg BD (secondary prophylaxis to prevent recurrent rheumatic fever)
• Digoxin: alternative rate control in AF

Surgical/Interventional

• Percutaneous mitral balloon valvuloplasty (PMBV): treatment of choice for symptomatic severe MS with favourable anatomy (Wilkins score ≤8), sinus rhythm or AF, no LA thrombus, and no more than mild MR
• Mitral valve replacement (MVR): if anatomy unfavourable for PMBV, significant MR, or failed PMBV
  • Mechanical: requires lifelong warfarin
  • Bioprosthetic: limited durability
• Closed mitral valvotomy: historical; rarely performed now

Referral Criteria

• Symptomatic severe MS: cardiology referral for intervention assessment
• New AF in MS: rate control and anticoagulation initiation
• Pregnancy with MS: specialist obstetric/cardiology joint care
• Systemic embolism: urgent evaluation

• Untreated symptomatic severe MS: 10-year survival ~50-60%
• Post-PMBV: good results with event-free survival ~60-70% at 10 years
• Post-MVR: 10-year survival ~70%
• AF in MS: significantly increases embolic risk (~5-15% per year without anticoagulation)
• Pregnancy with severe MS: high risk of maternal complications (pulmonary oedema, AF)
• Mild-moderate MS: can remain stable for decades

Wilkins Score for PMBV Suitability

MS Severity Grading