Mitral valve stenosis

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Here is a comprehensive overview of Mitral Valve Stenosis (MS) based on Harrison's Principles of Internal Medicine 22E, Schwartz's Principles of Surgery 11E, Braunwald's Heart Disease, and Fuster & Hurst's The Heart 15E.

Mitral Stenosis

Etiology

Rheumatic fever is the dominant cause, accounting for ~60% of pure MS cases. Chronic inflammation causes commissural fusion, chordal shortening, and calcification, producing the classic "fish-mouth" or funnel-shaped orifice. Other, less common causes include:

Congenital MS (parachute valve, cor triatriatum)
Severe mitral annular calcification with leaflet extension
Systemic lupus erythematosus / rheumatoid arthritis
Left atrial myxoma
Infective endocarditis with large vegetations
Prior chest radiation, mucopolysaccharidosis

MS has declined significantly in high-income countries but remains a major problem in sub-Saharan Africa, India, Southeast Asia, and Oceania.

Pathology

Rheumatic mitral stenosis — thickened, fused leaflets with a narrowed slit-like orifice viewed through a left atriotomy

Gross specimen: thickened, fused mitral leaflets with a severely narrowed orifice — classic rheumatic MS (Schwartz's Principles of Surgery)

The rheumatic process causes:

Diffuse leaflet thickening with fibrous tissue and calcium deposits
Commissural fusion — the commissures fuse, narrowing the orifice
Subvalvular involvement — chordae tendineae fuse and shorten
The valve assumes a funnel shape with doming leaflets
Later changes may be exacerbated by altered flow and ongoing inflammation

Pathophysiology

Parameter	Normal	Significant MS	Severe MS
MVA (cm²)	4–6	~2	≤1.5
Mean gradient (mmHg)	—	5–10	>10
PA systolic pressure (mmHg)	—	30–50	>50

When MVA falls below ~2 cm², the LA must generate an abnormally elevated pressure gradient to push blood into the LV. At MVA ≤1.5 cm² (severe MS), LA pressure of ~25 mmHg is required to maintain normal cardiac output.

Consequences in sequence:

Elevated LA pressure → left atrial enlargement
Pulmonary venous hypertension → dyspnea, orthopnea, pulmonary edema
Reactive pulmonary arterial hypertension — vasoconstriction + intimal hyperplasia ("second stenosis") — protects against acute pulmonary edema but reduces cardiac output
RV enlargement → secondary TR, PR, right-sided heart failure
Atrial fibrillation (AF) — develops due to LA dilation; tachycardia shortens diastolic filling time and dramatically worsens the gradient
Thromboembolism — LA thrombus (especially LA appendage) → stroke risk

Key hemodynamic point: Tachycardia is particularly dangerous because it shortens diastole proportionately more than systole, reducing filling time and sharply elevating LA pressure.

ACC/AHA Staging

Stage	Definition	MVA
A	Risk factors (e.g., rheumatic fever), normal flow velocities	Normal
B	Progressive MS, increased velocities	>1.5 cm²
C	Severe, asymptomatic	≤1.5 cm²
D	Severe, symptomatic	≤1.5 cm²

Symptoms

Exertional dyspnea — the first and most common symptom, triggered by exercise, pregnancy, fever, or AF with rapid ventricular rate
Orthopnea and paroxysmal nocturnal dyspnea
Hemoptysis — from pulmonary venous hypertension
Palpitations — from AF
Systemic embolism / stroke
Right-sided heart failure symptoms (edema, ascites) — in advanced disease

The latent period from rheumatic fever to symptoms is typically 20 years; progressive disability follows.

Physical Examination — The Auscultatory Triad

Loud S1 — abrupt closure of the thickened but still mobile mitral valve
Opening snap (OS) — the thickened valve snaps open; a shorter S2–OS interval = more severe stenosis (higher LA pressure)
Low-pitched mid-diastolic rumble at the apex, best heard in the left lateral decubitus position with the bell; pre-systolic accentuation in sinus rhythm

Note: In elderly patients with heavy calcification, the opening snap and loud S1 may be absent. The murmur may be soft with low stroke volume.

Investigations

ECG:

P mitrale — broad, notched P wave in lead II, biphasic in V1, indicating LA enlargement (in sinus rhythm)
With pulmonary hypertension: right axis deviation, RV hypertrophy
AF is common

Chest X-ray:

Straightening of the left heart border (LA enlargement)
Prominent main pulmonary arteries
Dilated upper lobe pulmonary veins
Kerley B lines — horizontal lines at the lung bases when resting mean LA pressure >20 mmHg

Echocardiography (gold standard):

TTE: measures transmitral velocities (E wave, A wave), mean gradient, MVA by pressure half-time or planimetry, pulmonary artery pressure, RV function
Wilkins score (echo score): assesses leaflet mobility, thickening, calcification, subvalvular involvement — critical for planning PMBC
TEE: superior imaging; mandatory before PMBC to exclude LA thrombus; especially useful when TTE is suboptimal

Multimodal echocardiographic findings in severe mitral stenosis: (A) Apical 4-chamber view with LA dilatation and thickened mitral leaflets; (B) Color Doppler showing turbulent diastolic flow; (C) Parasternal short-axis "fish-mouth" orifice; (D) Continuous-wave Doppler — MVA 1.02 cm² by pressure half-time

Echocardiographic hallmarks of severe MS: left atrial enlargement, turbulent diastolic inflow on color Doppler, fish-mouth orifice on short axis, and elevated diastolic gradient by CW Doppler

Cardiac catheterization: Reserved when there is discrepancy between clinical findings and noninvasive data.

Medical Management

Indication	Treatment
Pulmonary congestion	Na restriction + oral diuretics
Rate control in AF	Beta-blockers, non-DHP CCBs (verapamil/diltiazem), or digoxin
Anticoagulation (AF, prior embolism, or LA thrombus)	Warfarin (VKA), target INR 2–3
Anticoagulation in sinus rhythm with very enlarged LA (>5.5 cm)	Controversial; VKA generally used
Rheumatic fever prophylaxis	Penicillin (group A β-hemolytic streptococcal prevention)

⚠️ DOACs are contraindicated in rheumatic MS with AF. A 2022 NEJM trial (ATTMOSPHERE/INVICTUS) confirmed significantly higher mortality with rivaroxaban vs. VKA in rheumatic MS-associated AF. — Harrison's 22E, referencing Connolly SJ et al., NEJM 2022

Cardioversion of AF: Indicated if recent-onset AF in a patient not severe enough for intervention. Requires ≥3 weeks of therapeutic anticoagulation or TEE to exclude LA thrombus first.

Interventional Management

ACC/AHA management algorithm for rheumatic mitral stenosis — PMBC vs. MV surgery decision tree

FIGURE 274-2 from Harrison's 22E — ACC/AHA 2021 guideline management algorithm

Percutaneous Mitral Balloon Commissurotomy (PMBC)

Indications (Class I):

Symptomatic (NYHA II–IV) severe MS (MVA ≤1.5 cm² or <1 cm²/m² BSA), pliable valve, no significant MR (<2+), no LA thrombus
Asymptomatic severe MS + new AF or PASP >50 mmHg (Class 2a–2b)

Favorable anatomy (Wilkins score ≤8):

Pliable, non-calcified leaflets with minimal subvalvular involvement
Absence of significant MR

Contraindications: LA thrombus, significant (≥2+) MR, heavily calcified or immobile valve

Outcomes: Doubles MVA; 5-year event-free survival ~60–70% in well-selected patients

Surgical Options

Open commissurotomy:

Indicated for suitable anatomy when PMBC is not available or fails
Operative mortality <1%; freedom from reoperation ~80% at 20 years
Thromboembolic complications <1%/year

Mitral valve replacement (MVR):

Indicated when severe calcification/immobility precludes commissurotomy, or when significant MR coexists
Indication: severe MS (MVA ≤1.5 cm²), NYHA class III–IV despite optimal medical therapy
Peri-operative mortality typically <5% in young patients; rises to ≥10% in elderly with comorbidities
10-year survival in surgical survivors ~70%
Requires lifelong anticoagulation with mechanical prostheses

Complications

Complication	Mechanism
Atrial fibrillation	LA enlargement, LA myopathy
Systemic thromboembolism / stroke	LA thrombus (especially LA appendage)
Pulmonary hypertension	Passive + reactive (second stenosis)
Right heart failure	Severe PAH → RV dilation, TR
Hemoptysis	Pulmonary venous hypertension → bronchial vein rupture
Infective endocarditis	Turbulent flow, deformed valve
Recurrent rheumatic carditis	Ongoing streptococcal infection

Special Populations

Elderly: Loud S1 and OS often absent; calcified/immobile valve reduces PMBC success rates (<50%); MVR peri-operative mortality ≥10%.

Pregnancy: Tachycardia + increased blood volume can precipitate acute pulmonary edema in previously stable patients; PMBC can be performed during pregnancy (with radiation shielding).

Sources:

Harrison's Principles of Internal Medicine 22E (2025), Chapter 274 — Mitral Stenosis
Schwartz's Principles of Surgery 11E, Chapter 21 — Acquired Heart Disease
Braunwald's Heart Disease, Chapters 75 & relevant sections
ACC/AHA 2021 Guideline for Management of Valvular Heart Disease (Otto CM et al., Circulation 143:e72, 2021)

Recent literature note: A 2024 meta-analysis (PMID 37014563) on direct oral anticoagulants in AF + significant MS confirms that DOACs (rivaroxaban specifically) are associated with worse outcomes compared to VKA — consistent with current guidelines recommending warfarin for rheumatic MS.

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