CardiologyTier 1Disease (DEADMAN)

Mitral stenosis

Description

Obstruction to LV inflow -> diastolic transmitral gradient, inc LA pressure
Fixed lesion - output depends on diastolic filling time + atrial kick
- Anything shortening diastole decompensates: AF, tachycardia, fever, pregnancy

Severity	Valve area	Mean gradient	PASP
Normal	4-6 cm2	-	-
Mild	>1.5 cm2	<5 mmHg	<30 mmHg
Moderate	1.0-1.5 cm2	5-10 mmHg	30-50 mmHg
Severe	<1.0 cm2	>10 mmHg	>50 mmHg

Symptoms once area <1.5 cm2; rest symptoms <1.0 cm2
All consequences upstream - LV systolic function normal
- LA dilatation -> AF, thrombus
- Pulmonary venous HTN -> PHT -> RV failure, TR

F>M ~2:1
Almost entirely rheumatic -> follows ARF distribution
- Aboriginal and Torres Strait Islander Australians - among highest ARF/RHD rates worldwide
- Migrants from Pacific, SE Asia, Africa, Indian subcontinent
ARF -> symptoms: 20-40 yrs temperate, far shorter in endemic settings

Causes

Rheumatic - overwhelming majority
- Commissural fusion + leaflet thickening + chordal shortening -> fish-mouth orifice
Degenerative - mitral annular calcification; elderly, CKD, radiation
- Annular not commissural -> not valvotomy-amenable
Rare - parachute valve, carcinoid, SLE, RA, Fabry, MPS, ergot
Mimics - LA inflow obstruction with normal valve
- Myxoma, cor triatriatum, vegetation, pulmonary vein stenosis

Mechanism

Fixed orifice -> transmitral gradient
- inc LA pressure
- -> pulmonary venous congestion
- -> reactive pulmonary vasoconstriction, inc PVR
- -> RVH, TR, RV failure
Reactive PHT reverses after intervention; fixed component does not
AF -> loss of atrial kick + short diastole -> abrupt decompensation

Presentation

Exam

Tapping non-displaced apex, loud S1, opening snap, mid-diastolic rumble
- Bell, apex, left lateral, expiration
Severity = murmur duration + S2-OS interval, never intensity
- Short S2-OS -> high LA pressure -> severe
Pre-systolic accentuation only in sinus rhythm
Loud S1 and OS lost once valve calcified - severe disease can be quiet

Investigations

ECG: P mitrale, AF, RVH
CXR: LA enlargement, splayed carina, double density
TTE = diagnosis + severity
- Area (planimetry, pressure half-time), mean gradient, PASP, RV
- Wilkins score -> valvotomy suitability
TOE mandatory before any valvotomy - LA appendage thrombus
Stress echo if symptoms discordant with resting gradient
Cath only for clinical-echo discordance or pre-op coronary assessment

Medical therapy - all patients

Rate control - beta blocker or non-DHP CCB
- Lengthens diastole -> inc filling time -> dec LA pressure
Anticoagulation if AF, prior embolism, or LA thrombus
- Warfarin, INR 2-3
- DOACs contraindicated in rheumatic MS - INVICTUS showed warfarin superior
Congestion - loop diuretic, salt restriction
Secondary ARF prophylaxis - 4-weekly IM benzathine benzylpenicillin

Intervention

Intervene if:
- Severe (area <=1.5 cm2) and symptomatic, OR
- Asymptomatic with PASP >50 mmHg, new AF, prior embolism, or planned pregnancy
PBMV first-line if all of:
- Pliable, non-calcified valve (favourable Wilkins score)
- No LA thrombus on TOE
- MR less than moderate
Surgery (repair or replacement) if morphology unfavourable, LA thrombus, or significant MR
Balloon the pliable valve, cut the calcified one

Special situations

Pregnancy - beta blocker + diuretic; PBMV at 22-26 wks if refractory
- Decompensates mid-second trimester as CO peaks - intervene pre-conception
Endocarditis prophylaxis - not routine for native-valve MS
- Australian guidance does include Aboriginal and Torres Strait Islander people with RHD

Latent -> asymptomatic gradient -> exertional symptoms -> rest symptoms + PHT
Untreated 10-yr survival: ~80% asymptomatic, ~15% once NYHA III-IV
- Median survival <3 yrs once severe PHT established
New AF = the inflection point - decompensation risk + mandatory anticoagulation
PBMV not definitive - restenosis common, lifelong echo follow-up

Complications

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