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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Almost always caused by rheumatic heart disease (latent period 20–30 years after acute rheumatic fever)
- Low-pitched rumbling mid-diastolic murmur at apex, best heard in left lateral position with bell — preceded by an opening snap
- Key consequences: LA dilatation → AF → thromboembolism; pulmonary hypertension → right heart failure
- Anticoagulation with WARFARIN (not DOAC) if MS with AF — important exam distinction
- Percutaneous mitral balloon valvotomy for suitable valves (pliable, non-calcified, no significant MR); surgical valve replacement otherwise
Overview
Mitral stenosis (MS) is narrowing of the mitral valve orifice that impedes diastolic filling of the left ventricle. Rheumatic heart disease accounts for >95% of cases in the UK. Rheumatic inflammation causes commissural fusion, leaflet thickening, and chordal shortening. Rare non-rheumatic causes include severe mitral annular calcification (elderly), congenital MS, SLE, and carcinoid syndrome. Normal mitral valve area is 4–6 cm²; symptoms typically begin when the area falls below 2 cm², and severe MS is defined as <1 cm².
Epidemiology
MS is now rare in the UK due to the decline in rheumatic fever, but remains common globally (particularly South Asia, sub-Saharan Africa). When encountered in the UK, it is most often in older patients with a remote history of rheumatic fever, or in immigrants from endemic regions. Women are affected more commonly than men (2:1). There is a latent period of 20–30 years between acute rheumatic fever and symptomatic MS. Symptoms are often first unmasked by conditions that increase heart rate (pregnancy, AF, exercise, infection).
Clinical Features
Symptoms
Exertional dyspnoea (most common presenting symptom)
Palpitations (often due to AF)
Fatigue and reduced exercise tolerance
Haemoptysis (pulmonary venous hypertension, bronchial vein rupture)
Symptoms precipitated by pregnancy, exercise, AF, or infection
Hoarseness (Ortner syndrome — recurrent laryngeal nerve compression by dilated LA)
Stroke or peripheral embolism (especially with AF)
Signs
Malar flush (low cardiac output with pulmonary hypertension)
Low-pitched rumbling mid-diastolic murmur at apex, best heard with bell in left lateral position
Opening snap after S2 (the closer the OS to S2, the more severe the stenosis)
Loud S1 (pliable valve snaps shut)
Tapping apex beat (palpable loud S1)
AF (irregularly irregular pulse) — very common
Signs of pulmonary hypertension: loud P2, RV heave, raised JVP, peripheral oedema
Investigations
First-line
TTEConfirms diagnosis. Assess valve area (planimetry, pressure half-time), mean gradient, LA size, pulmonary artery systolic pressure, valve morphology (Wilkins score for suitability for balloon valvotomy)
ECGP mitrale (bifid P wave in lead II, >0.12 s), AF, RVH (if pulmonary hypertension)
Second-line
Chest X-rayLA enlargement (straightened left heart border, double shadow, splayed carina), pulmonary congestion, Kerley B lines, calcified mitral valve
TOEBetter valve morphology assessment; exclude LA appendage thrombus before intervention
Specialist
Cardiac catheterisationInvasive haemodynamics if non-invasive data discordant; pre-operative coronary assessment
Exercise echoAssess exercise-induced rise in gradient and pulmonary pressures in symptomatic patients with moderate MS
1
Medical management
- Rate control for AF: beta-blocker or rate-limiting CCB (diltiazem/verapamil)
- Anticoagulation: WARFARIN for MS with AF (DOACs are NOT recommended for MS with AF — mechanical/rheumatic valve indication)
- Diuretics for pulmonary congestion
- Antibiotic prophylaxis for secondary prevention of rheumatic fever (benzathine penicillin)
2
Percutaneous mitral balloon valvotomy (PMBV)
- First-line invasive treatment for symptomatic moderate-severe MS with favourable anatomy
- Favourable = pliable valve, minimal calcification, no significant MR, no LA thrombus (Wilkins score ≤8)
- High success rate with low procedural risk
3
Surgical intervention
- Mitral valve replacement (mechanical or bioprosthetic) for unsuitable valve morphology or failed PMBV
- Open surgical commissurotomy rarely performed now (PMBV preferred)
- Mechanical valve requires lifelong warfarin anticoagulation
Complications
- Atrial fibrillation: Most common complication — LA dilatation predisposes; increases stroke risk significantly
- Thromboembolism: LA stasis + AF → high risk of systemic embolism (stroke, peripheral arterial embolism)
- Pulmonary hypertension: Chronic elevated LA pressure transmitted to pulmonary vasculature
- Right heart failure: Secondary to pulmonary hypertension
- Infective endocarditis: Less common than in regurgitant lesions
- Haemoptysis: Pulmonary venous congestion and bronchial vein rupture
UKMLA Exam Tips
- 1MS + AF = WARFARIN — DOACs are NOT recommended (this is a high-yield exam distinction)
- 2The closer the opening snap to S2, the more severe the stenosis (higher LA pressure opens valve earlier)
- 3A quiet S1 and absent opening snap suggest severe calcification — unfavourable for PMBV
- 4Malar flush is a classic clinical sign — low cardiac output causes peripheral cyanosis with pulmonary congestion
- 5In pregnancy, MS symptoms worsen dramatically (increased blood volume + tachycardia → decreased diastolic filling time)
- 6MS is the ONLY valvular lesion where anticoagulation strategy differs between DOACs and warfarin in the context of AF
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