MITRAL STENOSIS

✓ Medically ReviewedDISEASEID: MDBT0157🚨 TRIAGE: URGENTICD-10: I05.0

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Definition

CLINICAL DEFINITION

A valvular heart disease characterised by the narrowing of the mitral valve orifice, impeding blood flow from the left atrium to the left ventricle during diastole, most commonly caused by rheumatic heart disease.

IN PLAIN ENGLISH

A condition where the heart's mitral valve becomes narrowed and stiff, making it harder for blood to flow from the upper left chamber to the lower left chamber.

COMMON MISCONCEPTION / WHAT IT DOES NOT MEAN

Mitral stenosis is NOT mitral regurgitation (where the valve leaks backward) and is NOT aortic stenosis (which affects the valve between the left ventricle and the aorta).

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Word Breakdown

mitr-

=funnel or thread (from Greek 'mitra', referring to the shape of the valve or a headband)

-stenosis

=narrowing or stricture (from Greek 'stenos')

Literal Meaning: Narrowing of the funnel-shaped valve

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Abbreviations

MS=Mitral Stenosis — standard abbreviation in cardiology

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Synonyms & Variants

Mitral Valve Stenosis›

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Category-Specific Context

As a valvular disease, mitral stenosis is classified by its aetiology (rheumatic versus non-rheumatic/degenerative) and severity based on valve area, mean transmitral gradient, and pulmonary artery systolic pressure.

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Clinical Context & Usage

CLINICAL SETTINGS

Cardiology ClinicEchocardiography LaboratoryEmergency DepartmentCardiothoracic Surgery Ward

USAGE & DOCUMENTATION NOTES

Often documented with severity grading (mild, moderate, severe) based on echocardiographic valve area (e.g., 'severe MS with MVA 0.9 cm²'). Notes frequently mention rhythm status (e.g., 'MS in AF') and anticoagulation management.

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Primary Causes & Pathophysiology

PATHOPHYSIOLOGY

Narrowing of the mitral valve orifice increases resistance to left ventricular inflow during diastole. This leads to elevated left atrial pressure, which transmits backward into the pulmonary vasculature, causing pulmonary venous hypertension and eventual right ventricular pressure overload. Chronic pressure overload results in left atrial dilation, predisposing to atrial fibrillation and thrombus formation. Over time, pulmonary hypertension can lead to right ventricular hypertrophy and right-sided heart failure.

PRIMARY CAUSES

Rheumatic Heart Disease

Autoimmune cross-reactivity following Group A streptococcal infection causes chronic inflammation, commissural fusion, and calcification of the mitral valve leaflets.

Degenerative Calcification

Age-related annular and leaflet calcification, often extending from the mitral annulus, restricting leaflet mobility in elderly patients.

Mediastinal Radiation Therapy

Late-onset fibrosis and calcification of the valve apparatus and annulus occurring years to decades after chest irradiation (e.g., for Hodgkin lymphoma or breast cancer).

Congenital Mitral Stenosis

Rare developmental anomalies such as parachute mitral valve or supravalvular mitral ring obstructing left ventricular inflow.

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Epidemiology

Prevalence:Rheumatic mitral stenosis remains highly prevalent in low- and middle-income countries, affecting millions globally. In high-income countries, the prevalence has significantly declined due to antibiotic treatment of streptococcal pharyngitis, with degenerative causes becoming relatively more common in the elderly.

Age Group:Rheumatic aetiology typically presents in young to middle-aged adults (20–50 years) in endemic regions. Degenerative or radiation-induced causes present in older adults (>65 years).

Sex Predilection:Female

Geographic Distribution:Highly prevalent in sub-Saharan Africa, South Asia, and parts of South America where rheumatic fever remains endemic. Rare in North America and Western Europe, where non-rheumatic causes predominate.

Red Flags & Triage ★

TRIAGE LEVEL

🚨 URGENT

DO NOT MISS — LIFE-THREATENING PRESENTATIONS

New-onset atrial fibrillation in a patient with mitral stenosis requires immediate assessment for left atrial appendage thrombus via TOE before cardioversion or percutaneous intervention, due to high embolic risk.
Haemoptysis or acute dyspnoea in a patient with known mitral stenosis raises concern for acute pulmonary oedema or pulmonary infarction secondary to severe pulmonary hypertension, requiring urgent echocardiographic and haemodynamic evaluation.

URGENT EVALUATION TRIGGERS

Acute onset of severe dyspnoea or orthopnoea suggesting acute pulmonary oedema.
New neurological deficit or transient ischaemic attack indicating systemic thromboembolism.
Rapid ventricular response in atrial fibrillation causing haemodynamic instability or acute heart failure.

Contraindications & Precautions

CONTRAINDICATIONS

Treadmill exercise testing is contraindicated in patients with severe symptomatic mitral stenosis due to the risk of precipitating acute pulmonary oedema or arrhythmias.
Pregnancy poses significant haemodynamic risks in severe uncorrected mitral stenosis; conception is generally contraindicated until the valve is intervened upon.

SPECIAL PRECAUTIONS

Strict heart rate control is essential
as tachycardia shortens diastolic filling time
exponentially increasing the transmitral gradient and pulmonary capillary wedge pressure.
Anticoagulation must be carefully managed
particularly in the presence of atrial fibrillation or prior embolic events
balancing stroke risk against bleeding risk.
Infective endocarditis prophylaxis is recommended according to local guidelines for patients with a history of rheumatic heart disease undergoing high-risk dental or respiratory procedures.

Complications

DOWNSTREAM CLINICAL COMPLICATIONS

Atrial fibrillation — loss of atrial kick and rapid ventricular response can acutely worsen pulmonary congestion.
Systemic thromboembolism — stasis in the dilated left atrium and left atrial appendage predisposes to stroke.
Pulmonary hypertension — chronic backward transmission of elevated left atrial pressure leads to right ventricular failure.
Infective endocarditis — although less common in pure stenosis than in regurgitation
damaged rheumatic valves remain susceptible.

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Reference Ranges

NORMAL RANGENormal mitral valve area is 4.0–6.0 cm².

CRITICAL (PANIC) VALUEMitral valve area < 1.0 cm² indicates severe stenosis, typically requiring intervention when symptomatic.

UNIT OF MEASUREMENTcm² (valve area), mmHg (pressure gradients)

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Confused With (LASA & DDx) ★

LEXICAL (LASA) — SIMILAR NAMES

Mitral Regurgitation

Both involve the mitral valve but represent opposite pathophysiological processes; stenosis is impaired forward flow during diastole, whereas regurgitation is backward flow during systole.

Aortic Stenosis

Both are stenotic valvular lesions causing pressure overload, but aortic stenosis affects the left ventricular outflow tract and presents with a systolic murmur, unlike the diastolic murmur of mitral stenosis.

CLINICAL DIFFERENTIAL DIAGNOSES (DDx)

Left Atrial Myxoma

Key Distinguishing Feature: Can mimic mitral stenosis haemodynamically and cause a 'tumour plop' on auscultation; distinguished by a mobile mass attached to the interatrial septum on echocardiography.

Severe Aortic Regurgitation (Austin Flint murmur)

Key Distinguishing Feature: The regurgitant jet can impinge on the anterior mitral leaflet, causing a functional mid-diastolic rumble; echocardiography confirms aortic root pathology and normal mitral valve anatomy.

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Clinical Pearls

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The classic auscultatory findings include a loud S1, an opening snap (OS) shortly after S2, and a low-pitched mid-diastolic rumble at the apex. The A2-OS interval inversely correlates with left atrial pressure; a shorter interval indicates more severe stenosis and higher left atrial pressure.

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Tachycardia is poorly tolerated in mitral stenosis because it disproportionately shortens diastole, the only phase when the left ventricle fills. Even mild sinus tachycardia or rapid atrial fibrillation can precipitate acute pulmonary oedema.

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Percutaneous balloon mitral valvuloplasty (PBMV) is the treatment of choice for symptomatic patients with favourable valve morphology (pliable, non-calcified leaflets, no significant subvalvular fusion, and absence of left atrial thrombus or moderate-to-severe mitral regurgitation).

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In pregnant patients with severe mitral stenosis, the physiological increase in blood volume and heart rate during the second trimester often precipitates heart failure; pre-conception counselling and intervention are strongly recommended.

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Example Usage & SOAP

CLINICAL SENTENCE

"The patient is a 42-year-old female with known rheumatic mitral stenosis, currently in atrial fibrillation with a controlled ventricular response, presenting with worsening NYHA class III dyspnoea."

IN A SOAP NOTE

S: 45-year-old female with a history of rheumatic heart disease presents with progressive exertional dyspnoea and palpitations over the past 3 weeks. O: BP 110/70 mmHg, HR 115 bpm irregularly irregular. Auscultation reveals a loud S1, opening snap, and grade 3/4 mid-diastolic rumble at the apex. Bilateral basal crackles. ECG shows atrial fibrillation with rapid ventricular response. TTE confirms severe mitral stenosis (MVA 0.9 cm², mean gradient 12 mmHg) with moderate pulmonary hypertension (PASP 55 mmHg). A: Severe rheumatic mitral stenosis complicated by new-onset atrial fibrillation with RVR and early pulmonary congestion. P: Admit for rate control with intravenous beta-blockers and diuresis. Initiate anticoagulation with LMWH bridging to warfarin. Schedule TOE to rule out left atrial appendage thrombus prior to considering percutaneous balloon mitral valvuloplasty or cardioversion.

DIFFERENTIAL DIAGNOSIS CONTEXT

Differential for a mid-diastolic apical murmur: (1) True mitral stenosis (structural leaflet thickening and commissural fusion on echo); (2) Austin Flint murmur (severe aortic regurgitation causing functional mitral obstruction, normal mitral leaflets); (3) Left atrial myxoma (mobile mass obstructing the mitral orifice, often with systemic symptoms and a 'tumour plop').

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Classifications & Scoring

SCORING TOOL

Wilkins Echocardiographic Score

Assesses mitral valve morphology to predict the success of percutaneous balloon mitral valvuloplasty. Scores leaflet mobility, valvular thickening, subvalvular thickening, and calcification from 1 to 4 each. A total score ≤ 8 indicates highly favourable anatomy for PBMV.

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Prognosis

SHORT-TERM OUTCOME

With appropriate medical management (rate control, diuretics, anticoagulation), acute symptomatic exacerbations can be stabilised. Percutaneous balloon mitral valvuloplasty (PBMV) offers immediate haemodynamic relief in suitable candidates.

LONG-TERM PROGNOSIS

Untreated severe mitral stenosis carries a poor prognosis, with 10-year survival dropping below 50% once symptoms like dyspnoea or pulmonary hypertension develop. Surgical or percutaneous intervention significantly improves long-term survival and symptom burden.

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References & Coding

ICD-10 DIAGNOSTIC CODE

I05.0

LITERATURE CITATIONS & GUIDELINES

[1]Otto CM, Nishimura RA, Bonow RO, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. J Am Coll Cardiol. 2021;77(4):e25-e197.

[2]Vahanian A, Otto CM, et al. 2021 ESC/EACTS Guidelines for the management of valvular heart disease. Eur Heart J. 2022;43(7):561-632.

[3]Carapetis JR, Beaton A, Cunningham MW, et al. Acute rheumatic fever and rheumatic heart disease. Nat Rev Dis Primers. 2016;2:15084.

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