Mitral Stenosis
Mitral stenosis is a narrowing of the mitral valve orifice, most commonly due to rheumatic heart disease, that obstructs blood flow from the left atrium to the left ventricle during diastole.
Mitral Stenosis (MS)
Mitral stenosis (MS) is the pathological narrowing of the mitral valve orifice, resulting in obstruction to diastolic blood flow from the left atrium (LA) into the left ventricle (LV). The name itself is instructive: "mitral" refers to the mitral valve (named after the bishop's mitre hat it resembles), and "stenosis" (Greek: stenos = narrow) means narrowing.
The normal mitral valve area (MVA) is 4–6 cm². Symptoms typically begin when the valve area falls below 2.5 cm², and haemodynamically significant stenosis occurs at < 1.5 cm². Critical mitral stenosis is defined as a valve area < 1.0 cm² [1][2].
Key Concept
The fundamental problem in MS is a fixed, narrowed orifice between the LA and LV. This creates a diastolic pressure gradient across the valve. Everything that follows — LA dilation, atrial fibrillation, pulmonary hypertension, right heart failure — is a downstream consequence of this single obstruction.
2. Epidemiology
- MS is overwhelmingly caused by rheumatic heart disease (RHD), accounting for ~95% of cases worldwide [2][3].
- RHD remains prevalent in developing nations (sub-Saharan Africa, South Asia, Southeast Asia, Pacific Islands) but has declined dramatically in developed countries due to improved sanitation, antibiotic treatment of Group A Streptococcal (GAS) pharyngitis, and better living standards.
- There is a female predominance (~2:1 F:M) in rheumatic MS, for reasons that are not entirely clear but may relate to autoimmune susceptibility.
- The latent period from acute rheumatic fever (ARF) to symptomatic MS is typically 20–40 years in temperate climates, but can be as short as 5–10 years in tropical/endemic regions [2].
- Hong Kong occupies an interesting epidemiological position. Historically, RHD was common. With modernisation, the incidence of acute rheumatic fever has fallen markedly, but a cohort of older patients (now aged 50–80+) who had rheumatic fever decades ago still presents with chronic rheumatic valvular disease.
- Degenerative mitral annular calcification (MAC) is becoming an increasingly important cause of MS in the elderly Hong Kong population, mirroring trends in other developed regions [1][3].
- Non-rheumatic causes (congenital, radiation-associated, SLE/RA, carcinoid) are rare but should be considered in the differential.
| Risk Factor | Mechanism |
|---|---|
| Previous acute rheumatic fever | Molecular mimicry → valvular inflammation → fibrosis and calcification |
| Recurrent GAS pharyngitis without adequate treatment | Each episode of ARF compounds valvular damage |
| Low socioeconomic status, overcrowding | Facilitates GAS transmission |
| Inadequate secondary prophylaxis (penicillin) | Allows recurrent ARF episodes |
| Advancing age (for degenerative MS) | Progressive mitral annular calcification |
| Female sex | 2:1 predominance |
| Radiation therapy (e.g. Hodgkin disease survivors) [2] | Radiation fibrosis of valve leaflets |
3. Anatomy and Function of the Mitral Valve
Understanding MS requires a solid grasp of the normal mitral valve apparatus, because the disease disrupts each component in a specific way.
The mitral valve is a complex structure with five functional components:
-
Mitral annulus — the fibrous ring that forms the structural frame of the valve, sitting at the atrioventricular junction. It is saddle-shaped (not flat), which helps distribute mechanical stress.
-
Two valve leaflets:
- Anterior (aortic) leaflet — larger, semi-circular, in fibrous continuity with the aortic valve (shares the intervalvular fibrosa with the left and non-coronary cusps of the aortic valve). Covers about 2/3 of the orifice area.
- Posterior (mural) leaflet — smaller, crescent-shaped, has three scallops (P1, P2, P3). Covers about 1/3 of the orifice area.
- The leaflets meet at the anterolateral and posteromedial commissures.
-
Chordae tendineae — fibrous cords that tether the free edges and undersurface of the leaflets to the papillary muscles. They prevent leaflet prolapse during systole.
-
Papillary muscles — two groups (anterolateral and posteromedial) arising from the LV free wall. Each papillary muscle sends chordae to both leaflets.
-
Left atrial and left ventricular myocardium — the contraction and relaxation of these chambers drives flow across the valve.
- During diastole, the LV relaxes and LV pressure drops below LA pressure → mitral valve opens → blood flows passively from LA to LV (early rapid filling phase, producing S3 if exaggerated). Late in diastole, atrial contraction ("atrial kick") contributes ~15–25% of LV filling.
- During systole, the LV contracts → rising LV pressure closes the mitral valve leaflets (producing S1). The chordae and papillary muscles prevent the leaflets from prolapsing into the LA.
- The normal transvalvular gradient in diastole is < 5 mmHg (essentially negligible).
Why the Mitral Valve is Vulnerable to Rheumatic Disease
The mitral valve is the valve most commonly affected by RHD (MV > AV > TV) [3]. This is likely because the left-sided valves operate under higher pressures and therefore sustain greater mechanical stress, making them more susceptible to immune-mediated inflammatory damage. The mitral valve in particular has a large surface area exposed to turbulent flow at the atrioventricular junction.
4. Aetiology
Rheumatic heart disease is the most common cause of mitral stenosis [1][2][3].
Pathogenesis of RHD (explained from first principles):
- Group A β-haemolytic Streptococcus (GAS) causes pharyngitis (strep throat).
- The M protein on the GAS surface shares structural homology with cardiac proteins (cardiac myosin, valve glycoproteins, laminin).
- Molecular mimicry: the host immune system generates antibodies (anti-M protein) that cross-react with cardiac self-antigens [3].
- This triggers an immune-mediated pancarditis (endocarditis, myocarditis, pericarditis) during acute rheumatic fever, occurring 2–6 weeks after the pharyngeal infection [3].
- The endocarditis component affects valve leaflets → small verrucae form along the line of closure → inflammation at the commissures.
- With recurrent episodes, the valves undergo progressive:
- Commissural fusion (the two commissures fuse together, narrowing the orifice)
- Leaflet thickening and fibrosis
- Chordal thickening, shortening, and fusion
- Calcification (late stage)
- The end result is a "fish-mouth" or "buttonhole" shaped stenotic valve.
Valve involvement in RHD: MV > AV > TV [3]. The pulmonary valve is almost never affected.
Acute Rheumatic Fever — Jones Criteria
Diagnosis requires 2 major OR 1 major + 2 minor criteria PLUS evidence of recent GAS infection (↑ASOT, positive rapid antigen test, positive throat culture, or recent scarlet fever) [3]:
Major criteria (mnemonic: J♥NES):
- Joints (migratory polyarthritis — large joints)
- ♥ Carditis (pancarditis — Carey-Coombs murmur is the mid-diastolic murmur of acute valvulitis)
- Nodules (subcutaneous, painless, over bony prominences)
- Erythema marginatum (evanescent, pink rings on trunk)
- Sydenham chorea (late manifestation, involuntary movements)
Minor criteria: fever, arthralgia, raised ESR/CRP, prolonged PR interval, previous RHD.
| Aetiology | Notes |
|---|---|
| Degenerative mitral annular calcification (MAC) | Increasingly common in elderly; heavy calcification of the annulus extends onto the leaflet bases, restricting motion. Risk factors overlap with atherosclerosis (age, HTN, DM, CKD, hyperlipidaemia) [1][2] |
| Congenital MS | Rare; includes parachute mitral valve (single papillary muscle), supravalvular mitral ring; presents in infancy [2] |
| Radiation-associated | Classically in Hodgkin disease survivors receiving mediastinal radiation [2]; fibrosis of leaflets |
| Infective endocarditis (IE) | Large vegetations can mechanically obstruct the orifice [1] |
| SLE / RA | Inflammatory valvulitis; Libman-Sacks endocarditis in SLE (sterile vegetations on the atrial side of MV) [1][2] |
| Carcinoid valve disease | Carcinoid syndrome causes fibrotic plaque deposition on right-sided valves primarily, but can rarely affect left-sided valves if there is a right-to-left shunt or bronchial carcinoid [2] |
| Mucopolysaccharidoses | Rare storage disorders causing glycosaminoglycan deposition in valve tissue [2] |
| Austin-Flint murmur (functional MS) | Not a true MS — the regurgitant jet of severe aortic regurgitation impinges on the anterior mitral leaflet, causing functional obstruction and a mid-diastolic rumble at the apex [1] |
When valve disease is not repairable... most mitral stenosis — no normal tissue to repair [4]. This is a critical surgical point: rheumatic MS distorts the valve so severely (fused commissures, thickened/calcified leaflets, shortened/fused chordae) that repair is rarely feasible, and replacement is usually required.
5. Pathophysiology
This is the most important section for understanding everything that follows. Every symptom, sign, investigation finding, and management decision flows from the pathophysiology.
In MS, the narrowed mitral valve creates obstruction to LV inflow [2]. Blood cannot flow freely from the LA into the LV during diastole. This establishes a diastolic pressure gradient across the mitral valve (transmitral gradient).
- Normally, mean LA pressure ≈ 5–10 mmHg, and the transmitral gradient is negligible.
- In MS, to maintain forward flow through a smaller orifice, LA pressure must rise, creating a significant transmitral gradient [2].
- The Gorlin formula relates valve area, flow rate, and gradient:
This means: for a given valve area, if you increase flow (e.g. exercise, tachycardia), the pressure gradient rises proportionally. This is why patients decompensate during high-output states.
5.2 Upstream Consequences (LA → Pulmonary Vasculature → Right Heart)
The pathophysiology proceeds in a predictable upstream cascade:
Let me walk through each step:
- The LA must generate higher pressure to push blood through the narrowed valve.
- Mean LA pressure rises from the normal ~8 mmHg to 20–30+ mmHg in severe MS.
- This gradient is diastolic — it exists throughout diastole and is maximal in early diastole (when the valve opens) and during atrial contraction (pre-systolic accentuation, if in sinus rhythm).
- Chronic pressure overload causes the LA to dilate (can become massively enlarged, sometimes the largest chamber in the heart).
- LA systole (atrial kick) becomes critically important for LV filling because the narrowed valve impedes passive early diastolic flow [2]. The atrial contraction generates a final "push" of blood across the stenotic valve.
- Consequence: anything that eliminates the atrial kick (i.e. AF) causes acute haemodynamic deterioration.
- LA dilatation stretches atrial myocytes and disrupts electrical conduction → predisposes to AF.
- Occurrence of AF is associated with acute cardiac decompensation [2] because:
- Loss of atrial kick reduces LV filling by 15–25%.
- Rapid ventricular rate shortens diastolic filling time (this is critical — flow across a stenotic valve is time-dependent; less time = less flow = more congestion).
- Both effects simultaneously increase LA pressure and reduce cardiac output.
- The dilated, fibrillating LA has sluggish blood flow, especially in the left atrial appendage (LAA).
- This creates ideal conditions for thrombus formation.
- Embolization: fragments break off and travel to the systemic circulation → stroke (most feared), mesenteric ischaemia, limb ischaemia, renal infarction [2].
- This is why anticoagulation is essential in MS with AF.
- Because the LA is in direct continuity with the pulmonary veins (no valves between them), elevated LA pressure is transmitted backwards into the pulmonary venous system.
- This causes pulmonary venous congestion → transudation of fluid into the interstitium and alveoli → pulmonary oedema.
pHTN in MS has two components:
- Passive component: direct back-transmission of elevated LA pressure into the pulmonary vasculature. This is proportional to the degree of LA hypertension.
- Reactive component: chronic elevation of pulmonary venous pressure triggers reactive pulmonary arteriolar vasoconstriction and late vascular remodelling (medial hypertrophy, intimal fibrosis of pulmonary arterioles) [2]. This adds a fixed, irreversible component of pulmonary vascular resistance on top of the passive component.
- The reactive component is actually a "double-edged sword" — it initially "protects" the pulmonary capillaries from flooding by limiting flow, but it also imposes a massive afterload on the right ventricle.
Why Pulmonary Hypertension in MS Can Be Very Severe
Unlike primary pulmonary hypertension (which only has the arteriolar component), MS-related pHTN has BOTH passive back-pressure AND reactive arteriolar changes. This is why pulmonary artery pressures in severe MS can exceed systemic pressures (PA systolic > 80 mmHg), and why prognosis is < 3 years once pHTN develops [2].
- The RV is a thin-walled, compliant chamber designed for a low-pressure system.
- Chronic pressure overload from pHTN causes RV hypertrophy → eventually RV dilatation and failure.
- RV failure leads to systemic venous congestion: elevated JVP, hepatomegaly, ascites, peripheral oedema [2].
- Functional tricuspid regurgitation (TR) develops as the RV dilates and the tricuspid annulus stretches.
- In pure MS, the LV is typically normal or may even be underfilled (low preload).
- LVEF is usually preserved (the problem is getting blood INTO the LV, not pumping it OUT).
- However, in ~25% of cases, there is mild LV dysfunction due to:
- Chronic underfilling
- Rheumatic myocardial involvement
- Reduced LV compliance from chronic underloading (disuse atrophy)
- Interventricular septal bowing from RV pressure overload
Acute decompensation occurs with conditions that increase heart rate or cardiac output [2]:
Any condition that:
- Increases heart rate (shortens diastolic filling time through the stenotic valve):
- Exercise, fever, anaemia, hyperthyroidism, pregnancy, AF, emotional stress
- Increases transvalvular flow (increases the gradient):
- Pregnancy (↑blood volume by 40%), anaemia (compensatory ↑CO), hyperthyroidism
- Eliminates atrial kick:
- New-onset AF
All of these increase the transmitral gradient and/or reduce LV filling → acute rise in LA pressure → flash pulmonary oedema.
The Pregnancy Problem in MS
MS is the valvular lesion least well tolerated in pregnancy. Why? Because pregnancy increases blood volume by ~40%, increases heart rate, and increases cardiac output — all of which dramatically increase the transmitral gradient in a fixed stenotic valve. Women with moderate-to-severe MS may present for the first time with pulmonary oedema during pregnancy, typically in the second trimester when blood volume peaks.
6. Classification
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Mitral valve area (MVA) | > 1.5 cm² | 1.0–1.5 cm² | < 1.0 cm² (critical) [1][2] |
| Mean transmitral gradient | < 5 mmHg | 5–10 mmHg | > 10 mmHg |
| PA systolic pressure | < 30 mmHg | 30–50 mmHg | > 50 mmHg |
| T½ (pressure half-time) | < 150 ms | 150–220 ms | > 220 ms |
Note: The pressure half-time (T½) is the time it takes for the peak transmitral gradient to fall to half its initial value. A longer T½ means slower emptying of the LA → more severe stenosis.
- Rheumatic (by far the most common)
- Degenerative (mitral annular calcification)
- Congenital
- Other (radiation, inflammatory, carcinoid, etc.)
The Wilkins echocardiographic score (also called the Massachusetts General Hospital score) grades mitral valve morphology on four parameters, each scored 1–4 (total score 0–16):
| Parameter | Score 1 (mild) | Score 4 (severe) |
|---|---|---|
| Leaflet mobility | Highly mobile, restricted only at tips | Immobile valve |
| Leaflet thickening | Near normal (4–5 mm) | Marked thickening (≥8–10 mm) |
| Subvalvular thickening | Minimal thickening just below leaflets | Extensive thickening extending to papillary muscles |
| Calcification | Single bright echo area | Extensive calcification throughout leaflets |
- Score ≤ 8: favourable morphology for percutaneous transvenous mitral commissurotomy (PTMC) [1]
- Score > 8: unfavourable; consider surgical intervention
7. Clinical Features
The clinical course of MS is insidious [2]:
- After the initial rheumatic fever episode, there is a long latent period (20–40 years in temperate regions, shorter in tropical regions) during which the valve progressively stenoses.
- 10-year survival > 80% if asymptomatic [2].
- 10-year survival becomes ~10% once symptomatic, and < 3 years if pulmonary hypertension develops [2].
- Early disease: insidious onset of SOB and ↓exercise tolerance [2]. Patients often unconsciously limit their activity, so they may not report symptoms until directly questioned.
- Acute decompensation can be the first presentation, triggered by conditions that ↑HR and ↑CO (fever, anaemia, hyperthyroidism, pregnancy, AF, exercise) [2] because these shorten diastolic filling time and increase the transvalvular gradient.
- Late disease: SOB at rest, orthopnoea, PND, right heart failure with systemic oedema [2]. Gross LA enlargement can cause compression of the recurrent laryngeal nerve (hoarseness — Ortner syndrome) and oesophagus (dysphagia) [2].
| Symptom | Pathophysiological Mechanism |
|---|---|
| Dyspnoea on exertion (most common presenting symptom) | ↑HR during exercise → ↓diastolic filling time → ↑transmitral gradient → ↑LA pressure → ↑pulmonary venous pressure → pulmonary congestion → stimulates J receptors in pulmonary interstitium → sensation of breathlessness [2] |
| Orthopnoea | Supine position → redistribution of blood from lower extremities to pulmonary vasculature (↑preload) → ↑pulmonary venous pressure → ↑pulmonary congestion [2] |
| Paroxysmal nocturnal dyspnoea (PND) | Same redistribution mechanism as orthopnoea, but delayed onset (1–2 hours after lying flat). Fluid gradually reabsorbed from peripheral oedema into intravascular space during recumbency → acute increase in pulmonary congestion awakens patient [2] |
| Cough | Pulmonary congestion irritates airway receptors → reflex cough [2] |
| Haemoptysis | Due to rupture of bronchial veins into the lung [1][2]. The bronchial veins drain into the pulmonary veins. When pulmonary venous pressure is chronically elevated, these thin-walled bronchial veins become engorged and can rupture, causing haemoptysis. Can also occur from frank pulmonary oedema (pink frothy sputum) or pulmonary infarction (if thromboembolism) |
| Palpitations | AF is very common (~45%) due to LA dilatation → irregular, often rapid ventricular response → patient perceives palpitations [1][2] |
| Decreased exercise tolerance (↓ET) | Fixed cardiac output — the stenotic valve limits the ability to increase CO during exercise → fatigue, weakness [1][2] |
| Hoarseness of voice (Ortner syndrome) | Enlarged LA compresses the left recurrent laryngeal nerve (RLN) [1][2]. The left RLN loops under the aortic arch and passes between the aorta and the pulmonary artery, directly adjacent to the LA. A massively dilated LA can compress it, causing left vocal cord paralysis and hoarseness |
| Dysphagia | Massive LA enlargement can compress the oesophagus posteriorly [2] |
| Systemic embolism (stroke, limb ischaemia) | LA stasis (from dilatation ± AF) → thrombus formation (especially in LAA) → embolisation to cerebral, mesenteric, renal, or peripheral arteries [2] |
| Right heart failure symptoms (peripheral oedema, abdominal distension, early satiety) | RV failure secondary to chronic pulmonary hypertension → systemic venous congestion → hepatic congestion (hepatomegaly, ascites), peripheral oedema [2] |
| Fatigue and weakness | Low forward cardiac output due to fixed obstruction at the mitral valve |
| Chest pain | Uncommon; may occur due to RV ischaemia from severe pHTN (RV demand-supply mismatch) |
Ortner Syndrome
Ortner's syndrome: LA enlargement → compression of left RLN → hoarseness of voice [1][2]. Remember this as a classic association with MS. The left RLN is vulnerable because of its long intrathoracic course, looping under the aortic arch and passing close to the LA and pulmonary artery. Any structure enlargement in this region (LA, pulmonary artery, aorta) can compress it.
7.3 Signs (with Pathophysiological Basis)
| Sign | Mechanism |
|---|---|
| Mitral facies (malar flush) | Cyanotic, plethoric cheeks with a bluish-red discolouration. Due to chronic low cardiac output → peripheral vasoconstriction and ↑deoxyhaemoglobin in the cutaneous capillary bed + chronic CO₂ retention from pulmonary congestion. Classic but uncommon in modern practice |
| Peripheral oedema | Right heart failure → systemic venous congestion → ↑hydrostatic pressure in peripheral capillaries → oedema |
| Raised JVP | Right heart failure. May have prominent 'a' wave (if pHTN and RV hypertrophy) or 'cv' wave (if functional TR) |
| Sign | Mechanism |
|---|---|
| Irregularly irregular pulse (AF) | LA dilatation → AF in ~45% of patients [2]. In early MS, may still be in sinus rhythm |
| Low-volume pulse | Low forward cardiac output through the fixed stenotic valve |
| Narrow pulse pressure [1] | Low stroke volume → ↓systolic pressure. The fixed obstruction limits forward flow → ↓pulse pressure |
| Sign | Mechanism |
|---|---|
| Apex beat: tapping (palpable S1) | In mild-moderate MS with a still-mobile valve, the forceful closure of the thickened but mobile mitral valve produces a palpable S1 ("tapping apex"). This is NOT a displaced or heaving apex — the LV is normal size or small |
| Apex is NOT displaced | In pure MS, the LV is normal size (underfilled if anything). A displaced apex suggests concomitant MR, AR, or LV dysfunction |
| Left parasternal heave | RV hypertrophy from pulmonary hypertension → sustained lift at the left sternal edge |
| Palpable P2 | Severe pHTN → forceful closure of the pulmonary valve → palpable at the left 2nd intercostal space |
| Diastolic thrill at apex | Palpable vibration corresponding to the diastolic murmur, felt in the left lateral decubitus position with the bell of the stethoscope |
This is the highest-yield section for clinical exams.
| Sign | Mechanism |
|---|---|
| Loud S1 | In mild-moderate MS, the valve leaflets are still mobile but their excursion is prolonged — at the onset of ventricular systole, the leaflets are still wide open (because the LA has been pushing blood through the narrowed orifice throughout diastole), so they travel a greater distance to close → louder snap. As MS becomes severe and the valve calcifies, S1 becomes soft because the leaflets lose mobility [5] |
| Opening snap (OS) | Occurs in early diastole when the thickened but still mobile mitral valve is forced open by the high LA pressure [1][2]. It is a brief, high-pitched sound heard best at the apex and left lower sternal border. The shorter the S2-OS interval, the more severe the MS (because higher LA pressure forces the valve open sooner) [2]. The OS disappears when the valve becomes heavily calcified and immobile |
| Low-pitched mid-diastolic rumbling murmur | The hallmark of MS. As blood flows through the narrowed valve orifice during diastole, turbulent flow produces a low-frequency rumble. Best heard at the apex with the bell of the stethoscope, in the left lateral decubitus position. Duration correlates with severity — a longer murmur suggests more severe stenosis [1] |
| Pre-systolic accentuation | If in sinus rhythm, atrial contraction at the end of diastole generates a final surge of blood through the stenotic valve → the murmur crescendos just before S1. This is absent in AF (because there is no organised atrial contraction) |
| Loud P2 | Forceful closure of the pulmonary valve due to pulmonary hypertension [1] |
| Graham Steell murmur | An early diastolic decrescendo murmur of pulmonary regurgitation (PR) due to severe pulmonary hypertension → dilatation of the pulmonary valve ring [1][2]. Best heard at the left 2nd–3rd intercostal space. It indicates severe, long-standing pHTN |
| Signs of pulmonary congestion | Bilateral basal lung crepitations from pulmonary oedema [1] |
| Signs of pulmonary hypertension | Loud P2, right parasternal heave, functional TR (pansystolic murmur at LLSB louder on inspiration — Carvallo's sign), raised JVP with prominent 'a' wave [1] |
High-Yield Auscultation Summary for MS
The classic auscultatory findings in MS are:
- Loud S1 (mobile valve) → becomes soft when calcified
- Opening snap (mobile valve opening under high LA pressure) → disappears when calcified
- Low-pitched mid-diastolic rumbling murmur at the apex, best with bell in left lateral decubitus
- Pre-systolic accentuation (if in sinus rhythm)
Severity indicators:
- Shorter S2-OS interval = more severe (higher LA pressure opens valve sooner)
- Longer murmur duration = more severe
- Presence of Graham Steell murmur and loud P2 = severe pHTN
- Soft S1 and absent OS = heavily calcified valve = severe MS but poor candidate for PTMC
Common Exam Mistake: S1 in MS
Students often state "S1 is loud in MS" without qualification. S1 is loud in MILD to MODERATE MS when the valve is still mobile. In SEVERE MS with a heavily calcified, immobile valve, S1 becomes SOFT. The same applies to the opening snap — it is present only when the valve retains some mobility and DISAPPEARS with severe calcification [5]. An examiner will test whether you know this distinction.
| Feature | Mild–Moderate MS | Severe MS |
|---|---|---|
| S1 | Loud | Soft (calcified) |
| Opening snap | Present; long S2-OS interval | Present but may disappear; short S2-OS interval |
| Murmur duration | Short | Long |
| Pre-systolic accentuation | Present (if sinus rhythm) | Present (if sinus rhythm) |
| Loud P2 | Absent | Present |
| Graham Steell murmur | Absent | Present |
| Parasternal heave | Absent | Present |
| Right heart failure signs | Absent | Present |
| Term | Definition | Significance |
|---|---|---|
| Ortner's syndrome | LA enlargement → compression of left RLN → hoarseness of voice [1][2] | Indicates massive LA dilatation |
| Graham Steell murmur | PR murmur associated with loud P2, indicating severe MS [1] | Indicates severe pHTN |
| Austin-Flint murmur | AR jet impinging on anterior mitral valve leaflet → functional MS [1] | A mimic of MS; no opening snap, S1 is normal/soft |
| Carey-Coombs murmur | Mid-diastolic murmur heard during acute rheumatic valvulitis | Transient; due to acute valvular inflammation, not structural stenosis |
| Carvallo's sign | TR = pansystolic murmur louder on inspiration [1] | Distinguishes TR from MR |
| P mitrale | Broad, bifid (notched) P wave in lead II (> 0.12s) on ECG | Indicates LA enlargement (hypertrophy/dilatation) |
Let me tie everything together in a single comprehensive flowchart:
High Yield Summary
Definition: Narrowing of the mitral valve orifice → obstruction to LV inflow in diastole. Critical MS: MVA < 1.0 cm².
Aetiology: Rheumatic heart disease (95%). Others: degenerative MAC, congenital, radiation (Hodgkin survivors), SLE, carcinoid.
Pathophysiology cascade: Stenotic MV → ↑transmitral gradient → ↑LA pressure → LA dilatation → AF (45%) + thromboembolism → ↑pulmonary venous pressure → pulmonary congestion + pHTN (passive + reactive) → RV failure → systemic venous congestion.
Decompensation triggers: Anything that ↑HR (shortens diastolic filling time) or ↑CO: exercise, fever, anaemia, pregnancy, hyperthyroidism, AF.
Key symptoms: Dyspnoea (most common), palpitations (AF), haemoptysis (bronchial vein rupture), hoarseness (Ortner syndrome), systemic embolism (stroke).
Key signs: Loud S1 (mild/mod) → soft S1 (severe/calcified). Opening snap (shorter S2-OS = more severe). Low-pitched mid-diastolic rumble at apex (bell, left lateral decubitus). Pre-systolic accentuation (if sinus rhythm). Loud P2 + Graham Steell murmur (severe pHTN). Narrow pulse pressure.
Surgical pearl: Most mitral stenosis cannot be repaired — no normal tissue to repair → valve replacement usually needed [4].
LV in MS: Typically normal size and function (the problem is upstream). Apex is NOT displaced.
Active Recall - Mitral Stenosis (Definition to Clinical Features)
[1] Senior notes: Maksim Medicine Notes.pdf (Cardiology section, pp. 35–38) [2] Senior notes: Ryan Ho Cardiology.pdf (pp. 152–155, Mitral Valve Diseases) [3] Senior notes: Maksim Medicine Notes.pdf (Rheumatic Heart Disease, p. 38) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p. 56 — "Most mitral stenosis — no normal tissue to repair") [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 31, 39 — Heart sounds and murmurs)
Differential Diagnosis of Mitral Stenosis
The differential diagnosis of mitral stenosis is really about two clinical questions:
- The patient presents with a mid-diastolic murmur at the apex — what else could cause this?
- The patient presents with dyspnoea, pulmonary congestion, and/or pulmonary hypertension — what other conditions mimic the haemodynamic picture of MS?
Let me work through this systematically, because the approach to differentiating these conditions teaches you a lot about cardiac physiology.
Heart valve problems in general: Stenosis = limited blood passing through → pressure overload; Regurgitation = large amount of blood going back → volume overload [6]. MS is a pressure-overload problem for the LA and pulmonary vasculature. Any condition that raises LA pressure or obstructs LV inflow will mimic MS haemodynamically. And any condition that produces a low-pitched diastolic rumble at the apex will mimic MS on auscultation.
A. Differential Diagnosis of the Mid-Diastolic Murmur at the Apex
This is the most exam-relevant framing. The hallmark murmur of MS is a low-pitched mid-diastolic rumble best heard at the apex with the bell in the left lateral decubitus position. Several other conditions can produce a similar murmur:
- Mechanism: In severe AR, the regurgitant jet from the aortic valve strikes the anterior mitral leaflet during diastole, partially closing it and restricting mitral inflow. This creates functional obstruction to LV filling, mimicking MS and producing a mid-diastolic rumble at the apex [1].
- How to distinguish from true MS:
- No opening snap (the mitral valve is structurally normal)
- S1 is normal or soft (not loud as in mild-moderate MS)
- Wide pulse pressure and other peripheral signs of AR (Corrigan's sign, de Musset's sign, Quincke's sign) — these are the opposite of the narrow pulse pressure seen in MS
- Associated with signs of severe AR: long diastolic murmur at the left sternal border, S3 [1]
- Echocardiography will show a normal mitral valve with severe AR and diastolic fluttering of the anterior mitral leaflet
Austin-Flint Murmur vs True MS
Austin-Flint murmur: AR jet impinging on anterior mitral valve leaflet → functional MS [1]. The key differentiator is the absence of an opening snap and the presence of wide pulse pressure and signs of AR. In an OSCE, if you hear a mid-diastolic rumble AND an early diastolic murmur at the left sternal edge → think Austin-Flint.
- Mechanism: During acute rheumatic fever, inflammation and oedema of the mitral valve leaflets cause a soft mid-diastolic murmur at the apex. This is NOT from structural stenosis but from acute inflammatory swelling of the leaflets and increased flow across an inflamed valve.
- How to distinguish from chronic rheumatic MS:
- Occurs in the acute setting of rheumatic fever (fever, migratory polyarthritis, raised inflammatory markers)
- Transient — resolves as the acute inflammation settles
- No opening snap (the valve is not structurally stenosed)
- May be accompanied by an MR murmur (pansystolic at apex)
- Evidence of recent GAS infection (↑ASOT, positive throat culture)
- Mechanism: A myxoma is the most common primary cardiac tumour. When it arises from the interatrial septum (usually on a stalk attached near the fossa ovalis) and prolapses through the mitral valve orifice during diastole, it physically obstructs LV inflow — mimicking MS both haemodynamically and on auscultation.
- Clinical features:
- Mid-diastolic rumble at the apex, sometimes with an audible "tumour plop" (low-pitched sound in early diastole, analogous to an opening snap but caused by the tumour hitting the LV wall)
- Postural variation: murmur intensity may change with body position (because the tumour moves with gravity). This is a classic distinguishing feature — true MS does not change with position
- Constitutional symptoms: fever, weight loss, elevated ESR/CRP (myxomas produce IL-6)
- Embolic events: tumour fragments or surface thrombi can embolise systemically
- Intermittent symptoms: patients may report episodic syncope or dyspnoea that worsens in certain positions and resolves in others
- How to distinguish from MS:
- No opening snap (no valve abnormality)
- Constitutional symptoms and elevated inflammatory markers
- Echocardiography is diagnostic — shows a mobile mass attached to the interatrial septum
- Mechanism: TS obstructs RV inflow, producing a mid-diastolic rumble at the left lower sternal border (LLSB), not the apex. Almost always rheumatic in origin and almost always accompanies MS (isolated TS is extremely rare) [3].
- How to distinguish from MS:
- Murmur is at the LLSB, not the apex
- Murmur increases with inspiration (increased venous return to right heart → more flow across the stenotic TV → louder murmur). This is in contrast to MS, where the murmur does not change significantly with respiration
- Signs of right-sided congestion predominate (elevated JVP with prominent 'a' wave, hepatomegaly, ascites, peripheral oedema) without prominent pulmonary congestion
- Echocardiography confirms TV pathology
- Mechanism: In severe MR, a large volume of blood regurgitates into the LA during systole. This increased volume then flows back across the mitral valve in diastole, producing a mid-diastolic flow murmur [1]. This is NOT stenosis — the valve is not narrowed — it is simply increased flow volume across a normal-sized (or even dilated) orifice.
- How to distinguish from MS:
- A prominent pansystolic murmur at the apex (the primary finding) precedes the diastolic rumble
- S3 is common (volume-overloaded LV)
- Displaced apex beat [1] (LV is dilated from volume overload — in pure MS, the apex is NOT displaced)
- No opening snap
- Echocardiography shows MR with normal valve area
- Mechanism: A significant left-to-right shunt at the atrial level (ASD) increases flow across the tricuspid valve → mid-diastolic flow murmur at LLSB. A VSD or PDA increases flow across the mitral valve → mid-diastolic flow murmur at the apex. These are flow murmurs, not stenosis.
- How to distinguish from MS:
- ASD: fixed splitting of S2, mid-diastolic murmur at LLSB (tricuspid flow murmur), no opening snap
- VSD: pansystolic murmur at LLSB + mid-diastolic rumble at apex (increased mitral flow)
- PDA: continuous "machinery" murmur at left infraclavicular area + mid-diastolic rumble at apex
- Echocardiography with colour Doppler identifies the shunt
- Mechanism: A rare congenital anomaly where a fibromuscular membrane divides the LA into two chambers — a proximal chamber receiving the pulmonary veins and a distal chamber communicating with the mitral valve. This creates obstruction to pulmonary venous drainage that mimics MS haemodynamically.
- Usually presents in childhood
- No opening snap, no characteristic MS murmur
- Echocardiography/CT/MRI identifies the membrane
B. Differential Diagnosis by Clinical Presentation
Sometimes the patient doesn't present with a murmur as the chief finding. They present with the consequences of MS — dyspnoea, pulmonary hypertension, right heart failure, or systemic embolism. Here, the differential broadens:
| Condition | Distinguishing Features |
|---|---|
| Left heart failure (HFrEF or HFpEF) | Displaced apex (if HFrEF), S3, no opening snap, no mid-diastolic rumble, CXR shows cardiomegaly with LV enlargement. ECG may show LVH. Echo: ↓LVEF or diastolic dysfunction |
| Other left-sided valvular disease (MR, AR, AS) | Each has characteristic murmurs (pansystolic for MR, early diastolic for AR, ejection systolic for AS). AS: low-volume, slow-rising pulse, narrow pulse pressure, heaving apex, systolic thrill [1]. AR: wide pulse pressure [1]. Echo confirms |
| Pulmonary disease (COPD, ILD, PE) | No cardiac murmur, spirometry/CT chest abnormal, no LA enlargement on echo |
| Primary pulmonary hypertension | No valvular abnormality on echo, no LA enlargement. Right heart catheterisation confirms pre-capillary pHTN with normal PCWP |
| Condition | Distinguishing Features |
|---|---|
| Hypertensive heart disease | History of hypertension, LVH on ECG/echo, no valvular stenosis |
| Hyperthyroidism | Thyroid signs (tremor, weight loss, goitre, eye signs), elevated fT4, suppressed TSH |
| Lone AF | No structural heart disease on echo |
| Other valvular disease with AF | Echo identifies specific valve lesion |
| Condition | Distinguishing Features |
|---|---|
| AF from any cause | MS is one of many causes of AF-related embolism |
| Infective endocarditis | Fever, positive blood cultures, vegetations on echo, Osler nodes, Janeway lesions |
| Left atrial myxoma | Constitutional symptoms, tumour plop, echo shows mass |
| Atherosclerotic disease | Carotid bruit, vascular risk factors, carotid Doppler/CT angiography |
| Paradoxical embolism (PFO/ASD) | Right-to-left shunt on bubble contrast echo |
| Condition | Distinguishing Features |
|---|---|
| Pulmonary embolism | Sudden pleuritic chest pain, tachycardia, CT pulmonary angiography positive |
| Bronchogenic carcinoma | Smoking history, weight loss, CT shows mass |
| Tuberculosis | Endemic area, constitutional symptoms, CXR cavitating lesion, sputum AFB |
| Bronchiectasis | Chronic cough with copious sputum, CT shows dilated airways |
| Goodpasture syndrome / pulmonary-renal syndromes | Concurrent renal failure, anti-GBM antibodies |
This is a frequent exam question. The two main categories of diastolic murmurs are:
| Murmur Type | Timing | Pitch | Best Heard | Classic Causes |
|---|---|---|---|---|
| Early diastolic (decrescendo) | Immediately after S2 | High-pitched | Left sternal border (AR), left 2nd ICS (PR) | Aortic regurgitation, Pulmonary regurgitation (Graham Steell murmur) [1][5] |
| Mid-to-late diastolic (rumble) | After opening snap, mid-diastole | Low-pitched | Apex (MS), LLSB (TS) | Mitral stenosis, Tricuspid stenosis, Austin-Flint murmur, LA myxoma, flow murmurs [5] |
The Key Distinction
Early diastolic murmurs (AR, PR) are HIGH-pitched and DECRESCENDO — they start loud just after S2 and fade. Mid-diastolic murmurs (MS, TS) are LOW-pitched and RUMBLING — they occur after an opening snap and may crescendo before S1 (pre-systolic accentuation in sinus rhythm). If you can identify the timing and pitch, you're 80% of the way to the diagnosis [5].
| Condition | Murmur | Opening Snap | Pulse Pressure | Apex | S1 | Key Distinguishing Feature |
|---|---|---|---|---|---|---|
| Mitral Stenosis | Mid-diastolic rumble, apex | Present (if mobile valve) | Narrow [1] | Not displaced (tapping) | Loud (mild-mod), soft (severe) | Opening snap + mid-diastolic rumble |
| Austin-Flint | Mid-diastolic rumble, apex | Absent | Wide [1] | May be displaced (LV dilatation from AR) | Normal/soft | Co-existing AR murmur, wide pulse pressure |
| LA Myxoma | Mid-diastolic rumble ± tumour plop | Absent | Variable | Not displaced | Variable | Postural variation, constitutional Sx, echo mass |
| Carey-Coombs | Soft mid-diastolic, apex | Absent | Normal | Not displaced | Normal | Acute rheumatic fever setting, transient |
| Tricuspid Stenosis | Mid-diastolic rumble, LLSB | Absent at apex (may have OS at LLSB) | Normal | Not displaced | Normal S1, may have loud T1 | LLSB location, louder on inspiration |
| Severe MR flow murmur | Mid-diastolic after prominent PSM | Absent | Normal/low | Displaced [1] | Soft (MR) | Prominent pansystolic murmur, S3 |
| ASD flow murmur | Mid-diastolic, LLSB | Absent | Normal | Not displaced | Normal | Fixed split S2, tricuspid flow murmur |
High Yield Summary
The mid-diastolic murmur DDx can be remembered by asking three sequential questions:
- Where is it? Apex = MS, Austin-Flint, LA myxoma, MR flow murmur, Carey-Coombs. LLSB = TS, ASD flow murmur.
- Is there an opening snap? If yes → likely true MS. If no → consider the other causes.
- What else is present? AR murmur + wide pulse pressure → Austin-Flint. Pansystolic murmur + displaced apex → MR flow. Postural variation + constitutional symptoms → LA myxoma. Acute fever + migratory arthritis → Carey-Coombs.
Echocardiography is the definitive investigation to distinguish all of these conditions — it directly visualises valve morphology, measures valve area and gradients, detects masses, and identifies shunts [1][6].
The clinical importance of the differential is that management is completely different: MS may need PTMC or valve replacement, Austin-Flint needs AR management, LA myxoma needs surgical excision, and flow murmurs need treatment of the underlying lesion.
Active Recall - Differential Diagnosis of Mitral Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (Cardiology section, pp. 35–36) [2] Senior notes: Ryan Ho Cardiology.pdf (pp. 152–155, Mitral Valve Diseases) [3] Senior notes: Maksim Medicine Notes.pdf (Rheumatic Heart Disease, p. 38; Valvular terminologies, p. 37) [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 22, 31, 39 — Heart sounds, murmurs, facies) [6] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (pp. 33, 45, 52, 56)
Diagnosis of Mitral Stenosis
The diagnosis of mitral stenosis rests on three pillars: (1) clinical suspicion from history and examination, (2) confirmation and severity grading by echocardiography (the gold standard), and (3) assessment of consequences and suitability for intervention using adjunctive investigations. There is no single "diagnostic criterion" set like Jones criteria for ARF — instead, we integrate clinical and echocardiographic findings.
Let me walk through each investigation systematically, explaining what you're looking for, what you find, and why.
1. Diagnostic Criteria for Mitral Stenosis
Unlike some conditions, MS does not have formal "diagnostic criteria" in the way rheumatic fever has the Jones criteria. The diagnosis is established by echocardiography demonstrating a narrowed mitral valve orifice with a diastolic transmitral pressure gradient. The clinical assessment provides the suspicion; echo provides the confirmation.
This table is what you use to classify severity once echocardiography confirms MS:
| Parameter | Normal | Mild MS | Moderate MS | Severe MS |
|---|---|---|---|---|
| Mitral valve area (MVA) | 4–6 cm² | > 1.5 cm² | 1.0–1.5 cm² | < 1.0 cm² (critical) [1][2] |
| Mean transmitral gradient | < 2 mmHg | < 5 mmHg | 5–10 mmHg | > 10 mmHg |
| PA systolic pressure | < 25 mmHg | < 30 mmHg | 30–50 mmHg | > 50 mmHg |
| Pressure half-time (T½) | < 60 ms | < 150 ms | 150–220 ms | > 220 ms |
Why pressure half-time? The pressure half-time (T½) is the time it takes for the peak transmitral pressure gradient to decay to half its initial value. A narrower orifice means blood takes longer to equilibrate between LA and LV → longer T½. The MVA can be estimated from T½ using the empirical formula: MVA = 220 ÷ T½ (in cm²). This is particularly useful when direct planimetry is technically difficult.
While echocardiography is definitive, the classic auscultatory triad that makes you highly confident of MS before you even order the echo is:
- Loud S1 (if valve still mobile)
- Opening snap [1]
- Low-pitched mid-diastolic rumbling murmur at the apex [1][5]
If all three are present, the positive predictive value for MS is extremely high. But remember — severe calcified MS may lack the first two, leaving only the murmur (which can be very soft and easily missed if you don't position the patient in the left lateral decubitus and use the bell).
The following flowchart represents the systematic approach from clinical suspicion to definitive diagnosis and assessment for intervention:
3. Investigation Modalities: Detailed Findings and Interpretation
The ECG is usually the first investigation you get. It won't diagnose MS, but it shows the electrical consequences of the haemodynamic derangement.
| Finding | Pathophysiological Basis | Interpretation |
|---|---|---|
| P mitrale [1] | LA pressure overload and dilatation causes the left atrial component of the P wave to become prolonged. Normal P wave duration < 0.12s; in P mitrale, the P wave becomes broad (> 0.12s) and notched/bifid in lead II, with a dominant negative deflection in V1 (> 1mm deep and > 1 small square wide) | Indicates LA enlargement — highly suggestive of left-sided valvular disease, especially MS |
| Atrial fibrillation (AF) [1][2] | LA dilatation stretches atrial myocytes, disrupts normal electrical conduction pathways, and creates re-entrant circuits → AF. Occurs in ~45% of patients with MS | Irregularly irregular rhythm, absent P waves, fibrillatory baseline. Important because it triggers anticoagulation and rate control |
| Right axis deviation | RV hypertrophy from chronic pHTN shifts the mean QRS axis rightward (> +90°) | Indicates significant pulmonary hypertension with RV remodelling |
| RV hypertrophy pattern | Chronic pressure overload on the RV → increased RV muscle mass | Tall R wave in V1 (R > S), right axis deviation, right ventricular strain pattern (ST depression + T wave inversion in V1–V3 and inferior leads) |
| Right bundle branch block (RBBB) | RV dilatation may stretch the right bundle branch | RSR' pattern in V1–V2, wide QRS (> 0.12s) |
ECG in MS — What to Look For
ECG: AF, P mitrale [1]. These are the two key ECG findings in MS exams. If you see a bifid P wave in lead II with an irregularly irregular rhythm in a young woman with dyspnoea → think MS until proven otherwise. Add right axis deviation and RVH pattern if pHTN has developed.
The CXR shows the structural and pulmonary consequences of MS. It's a readily available, inexpensive investigation that provides a lot of diagnostic information.
| Finding | Pathophysiological Basis | How to Identify |
|---|---|---|
| LA enlargement [1] | Chronic pressure overload → LA dilatation | Four CXR signs of LA enlargement: (1) Double right heart border (the enlarged LA projects behind the right atrium on PA view, creating a second density within the right heart silhouette). (2) Splaying of the carina (the left main bronchus is pushed upward by the enlarged LA sitting directly below the carina — the angle between the two main bronchi widens to > 90°). (3) Straightening of the left heart border (the enlarged LA appendage fills in the normal concavity between the pulmonary trunk and LV on the left heart border). (4) Posterior displacement of the oesophagus (seen on lateral view or barium swallow — the LA pushes the oesophagus backwards) |
| Pulmonary congestion [1] | ↑pulmonary venous pressure from ↑LA pressure | Upper lobe pulmonary venous distension (normally, lower lobe veins are larger due to gravity; when pulmonary venous pressure rises > 15 mmHg, upper lobe veins distend — "cephalization" or "upper lobe blood diversion"). Kerley B lines (short horizontal lines at the lung periphery, especially at the costophrenic angles, representing thickened interlobular septa from interstitial oedema). Bilateral perihilar haziness (bat-wing pattern) in acute pulmonary oedema. Pleural effusions (usually bilateral, may be right-sided dominant) |
| Prominent pulmonary arteries [1] | Pulmonary hypertension → dilatation of the main pulmonary artery and its branches | Enlarged pulmonary trunk (the second "bump" on the left heart border becomes prominent). Enlarged hilar pulmonary arteries. In severe pHTN with reactive arteriolar remodelling, the peripheral lung fields may appear oligaemic ("pruning" — large proximal arteries with absent peripheral vessels) |
| Normal or small LV | In pure MS, the LV is underfilled (the obstruction is proximal to it) | The cardiothoracic ratio may be normal or only mildly increased. If the LV is enlarged, think of concomitant MR, AR, or LV dysfunction |
| Mitral valve calcification | Long-standing RHD → progressive calcification of valve leaflets | May be visible as dense calcification in the region of the mitral valve on lateral view. Better assessed by CT or fluoroscopy |
CXR in MS vs Other Causes of Cardiomegaly
A common exam mistake is to interpret the CXR of MS as simply "cardiomegaly." In pure MS, the heart may NOT be significantly enlarged overall — the LA is massively dilated but the LV is normal. The classic CXR shows LA enlargement (double right heart border, splaying of carina) + pulmonary congestion + prominent pulmonary arteries [1] — but with a relatively normal-sized LV. If you see a massively dilated LV, consider concomitant MR or other pathology.
3.3 Echocardiography (The Gold Standard)
Echocardiography is the single most important investigation for MS [1][6]. It confirms the diagnosis, grades severity, assesses valve morphology for procedural planning, evaluates concomitant valve lesions, and estimates pulmonary artery pressure.
TTE is the first-line echocardiographic modality [1][7].
What TTE Tells You in MS:
| Assessment | Specific Findings | Clinical Significance |
|---|---|---|
| Valve morphology | Thickened leaflets, restricted leaflet motion ("hockey stick" appearance of the anterior leaflet in the parasternal long-axis view — the leaflet tip is tethered while the body domes forward). Commissural fusion (the two commissures are stuck together, best seen in parasternal short-axis view — the valve opens like a "fish-mouth" instead of a wide orifice). Chordal thickening and shortening. Calcification (bright echogenic areas with acoustic shadowing) | Determines aetiology (rheumatic morphology is characteristic) and suitability for PTMC (Wilkins score) |
| Mitral valve area (MVA) [1] | Measured by: (1) Direct planimetry in parasternal short-axis view (trace the inner edge of the valve orifice at the tips of the leaflets — gold standard measurement). (2) Pressure half-time (T½) method: MVA = 220/T½. (3) Continuity equation. (4) PISA method (proximal isovelocity surface area — less commonly used for MS) | < 1 cm² = critical [1][2]. This is the primary determinant of severity |
| Mean transmitral gradient | Measured by continuous-wave Doppler across the mitral valve. The Doppler signal traces the velocity of blood flow through the narrowed orifice. Using the simplified Bernoulli equation (ΔP = 4V²), the gradient is calculated | > 10 mmHg at rest = severe. Note: the gradient is flow-dependent — it can be misleadingly low in low-output states (e.g. severe RV failure) and misleadingly high in high-output states (e.g. anaemia, pregnancy) |
| PA systolic pressure (PASP) | Estimated from the peak TR velocity using the simplified Bernoulli equation: PASP = 4 × (TR velocity)² + estimated RAP | > 50 mmHg = severe pHTN [1]. Important prognostic marker and indication for intervention |
| LV and RV function | LV size (should be normal in pure MS), LVEF (usually preserved), RV size and function (may show RV dilatation and dysfunction in severe pHTN) | Underfilled LV supports pure MS. RV dysfunction indicates advanced disease |
| Rule out concomitant MR [1] | Colour Doppler shows any mitral regurgitant jet. Grade MR severity | Concomitant moderate-severe MR is a contraindication for PTMC [1] — the commissurotomy balloon can worsen MR |
| Other valve lesions | Assess for concomitant AS, AR, TS, TR | Rheumatic disease often affects multiple valves (MV > AV > TV) [3] |
| LA size and LAA thrombus | LA dimension, LA volume. TTE has limited sensitivity for LAA thrombus (LAA is a posterior structure, poorly visualised by TTE) | LA dilatation quantifies disease burden. LAA thrombus is a contraindication for PTMC [1] — requires TOE for reliable exclusion |
TOE is indicated when TTE is inadequate or for specific pre-procedural assessment [7].
| Indication | Why TOE is Superior |
|---|---|
| Detection of LAA thrombus | The LAA is a posterior structure that is poorly visualised by TTE (the ultrasound beam has to travel through the entire chest). TOE places the probe directly behind the LA in the oesophagus, giving excellent near-field views of the LAA [7]. Sensitivity for LAA thrombus: TTE ~40–50% vs TOE > 95% |
| Detailed valve morphology | Higher resolution images of leaflet thickening, commissural fusion, and calcification. Critical for accurate Wilkins scoring when TTE images are suboptimal |
| Assessment of MR severity | More accurate grading of concomitant MR, especially in cases where TTE is equivocal |
| Prosthetic valve assessment | Prosthetic valves cause acoustic shadowing that limits TTE. TOE avoids this by imaging from behind the valve [7] |
| Guidance during PTMC | TOE is used intra-procedurally to guide transseptal puncture, monitor balloon positioning, and assess the result in real time |
Must-Do Before PTMC
Before PTMC, you MUST perform TOE to: (1) Exclude LAA thrombus (contraindication — the catheter passes through the LA, and dislodging a thrombus could cause stroke). (2) Confirm no more than mild MR. (3) Assess Wilkins score to confirm favourable morphology (≤ 8). If any of these are unfavourable, PTMC is contraindicated [1].
| Indication | What It Adds |
|---|---|
| Discrepancy between symptoms and resting echo severity | Some patients are very symptomatic but have only moderate MS at rest. With exercise, heart rate rises → diastolic filling time shortens → transmitral gradient increases dramatically. Exercise echo can unmask haemodynamically significant MS that appears only moderate at rest |
| Assessment of exercise-induced pHTN | PA pressure may be normal at rest but rise significantly with exercise (> 60 mmHg with exercise = haemodynamically significant). This can tip the balance toward intervention |
| Assessment of functional capacity | Objective measurement of exercise tolerance in patients who deny symptoms |
Why does the gradient increase with exercise? The Gorlin formula shows that for a fixed valve area, the gradient increases with the square of the flow rate. During exercise, cardiac output increases → more flow across the valve → gradient rises disproportionately. Additionally, the shortened diastolic filling time means the LA has less time to empty → higher end-diastolic LA pressure.
Coronary angiogram is performed pre-operatively [1].
| Indication | Rationale |
|---|---|
| Pre-operative assessment | To rule out concomitant coronary artery disease and assess need for CABG [1]. If significant CAD is present, CABG can be performed at the same time as valve surgery |
| Age thresholds | Generally indicated in: men > 40 years, women > 50 years (or postmenopausal), any patient with angina or cardiovascular risk factors |
| Alternative to invasive angiography | CT coronary angiography is increasingly used as a non-invasive alternative, especially in lower-risk patients |
While largely superseded by echocardiography for diagnosis, invasive haemodynamic assessment is still used in specific situations:
| Indication | What It Measures |
|---|---|
| Discordance between clinical and echo findings | Direct measurement of: LA pressure (via pulmonary capillary wedge pressure/PCWP), PA pressure, transmitral gradient, cardiac output (thermodilution or Fick method), and calculation of MVA using the Gorlin formula [3] |
| Assessment of pulmonary vascular resistance | Differentiates passive from reactive pHTN — important for surgical risk assessment. If PVR is very high (> 6 Wood units) and fixed (doesn't fall with vasodilator testing), surgical risk is significantly increased |
| Combined with coronary angiography | Often performed at the same sitting |
The Gorlin formula: Estimates valve area from pressure gradient, flow rate, heart rate, and CO [3]. MVA = CO / (DFP × HR × 44.3 × √ΔP), where DFP = diastolic filling period, and ΔP = mean transmitral gradient. This is the invasive gold standard for valve area calculation but requires catheterisation.
| Modality | Role in MS |
|---|---|
| Cardiac CT | Excellent for quantifying mitral annular and leaflet calcification (calcium scoring). Can visualise LA thrombus (though TOE remains superior for LAA). CT coronary angiography as a non-invasive alternative to invasive angiography. Useful for pre-surgical anatomical planning |
| Cardiac MRI | Can measure MVA by direct planimetry (similar to echo). Quantifies LV and RV volumes and function with high accuracy. Measures transmitral flow and gradient. Less operator-dependent than echo. However, NOT first-line — used when echo is inadequate or for research |
While not diagnostic of MS itself, blood tests are essential for identifying precipitating factors, complications, and pre-procedural workup:
| Test | Rationale |
|---|---|
| CBC | Anaemia (can precipitate decompensation by ↑CO), polycythaemia (chronic hypoxia from severe pHTN) |
| Thyroid function tests (TFTs) | Hyperthyroidism is a reversible cause of AF and can precipitate decompensation in MS. Always check TFTs when AF is newly diagnosed |
| Renal function tests (RFT) | Baseline before contrast administration (angiography) and before starting anticoagulation. Renal impairment from chronic low CO or renal embolism |
| Coagulation profile | Baseline before anticoagulation. Also important if liver congestion from RHF is causing synthetic dysfunction |
| Liver function tests (LFTs) | Hepatic congestion from RHF → elevated transaminases, elevated bilirubin, low albumin (congestive hepatopathy / cardiac cirrhosis) |
| BNP / NT-proBNP | Elevated in heart failure. Correlates with symptom severity and pHTN. Useful for monitoring and prognostication |
| Inflammatory markers (ESR, CRP) | If considering active rheumatic carditis, IE, or LA myxoma |
| ASOT / Anti-DNAse B | If suspecting acute rheumatic fever as the cause |
| Blood cultures | If infective endocarditis is in the differential |
| Stage | Investigation | Key Question Answered |
|---|---|---|
| Bedside | History + Examination | Is MS likely? What is the clinical severity? |
| First-line | ECG [1] | AF? P mitrale? RVH? |
| First-line | CXR [1] | LA enlargement? Pulmonary congestion? pHTN signs? |
| Definitive | TTE [1][6] | Confirmed MS? MVA? Gradient? PASP? Valve morphology? Concomitant MR? Wilkins score? |
| Pre-intervention | TOE [7] | LAA thrombus? Detailed morphology? MR grade? Intra-procedural guidance |
| If discordant | Exercise echo | Exercise-induced gradient? Exercise pHTN? |
| Pre-operative | Coronary angiography [1] | Concomitant CAD needing CABG? |
| Selected cases | Right heart catheterisation | Direct haemodynamics? PVR? Gorlin formula MVA? |
| Adjunctive | Blood tests | Precipitants? Complications? Pre-procedural fitness? |
High Yield Summary
No formal diagnostic criteria — diagnosis is established by echocardiography showing a narrowed mitral valve with ↑diastolic transmitral gradient [1][2].
Severity grading (echo): MVA > 1.5 cm² = mild; 1.0–1.5 cm² = moderate; < 1.0 cm² = critical (severe) [1][2]. Mean gradient > 10 mmHg and PASP > 50 mmHg also indicate severe MS.
ECG: AF, P mitrale [1] + RVH/RAD in advanced disease.
CXR: LA enlargement (double right heart border, splaying of carina), pulmonary congestion, prominent pulmonary arteries [1]. LV is normal size in pure MS.
TTE is the gold standard: confirms diagnosis, grades severity (MVA, gradient, PASP), assesses morphology (Wilkins score for PTMC eligibility), and rules out concomitant severe MR [1].
TOE: Essential pre-PTMC to exclude LAA thrombus [1][7]. Superior for posterior structures (LA, LAA, MV).
Coronary angiography: Pre-operative to rule out CAD and assess need for CABG [1].
Wilkins score ≤ 8 = favourable for PTMC. Contraindications for PTMC: moderate-severe MR, LAA thrombus, heavily calcified valve [1].
Active Recall - Diagnosis of Mitral Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (Cardiology section, pp. 35–37) [2] Senior notes: Ryan Ho Cardiology.pdf (pp. 152–155, Mitral Valve Diseases) [3] Senior notes: Maksim Medicine Notes.pdf (Rheumatic Heart Disease, p. 38; Terminologies including Gorlin formula, p. 37) [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 39 — Murmur diagrams and locations) [6] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (pp. 33, 45, 52 — Diagnosis of valvular disease) [7] Senior notes: Maksim Medicine Notes.pdf (Echocardiography, p. 6 — TEE indications)
Management of Mitral Stenosis
Let me start with the overarching philosophy, because it frames everything:
There is no medication that can fix a stenotic mitral valve [6]. No drug will prise open fused commissures or dissolve calcified leaflets. Medical therapy is purely palliative — it manages the consequences of MS (pulmonary congestion, AF, thromboembolism) while the patient awaits definitive intervention or if they are not candidates for it.
The indication for surgery is: severe valve problem with symptoms OR ventricular dysfunction [6]. This is the universal principle for all valvular heart disease.
The management approach therefore has three tiers:
- Medical therapy — symptom control and complication prevention
- Percutaneous intervention — PTMC/PMBV for suitable candidates
- Surgical intervention — commissurotomy or valve replacement when percutaneous options are not feasible
1. Medical Therapy
Medical therapy does NOT alter the natural history of MS. It manages symptoms and complications while you plan for definitive intervention.
| Drug | Mechanism | Rationale in MS |
|---|---|---|
| Loop diuretics (furosemide/frusemide) | Inhibit Na⁺/K⁺/2Cl⁻ co-transporter in thick ascending limb of loop of Henle → ↑urinary Na⁺ and water excretion → ↓intravascular volume → ↓preload | By reducing intravascular volume, you reduce LA filling pressure → reduce pulmonary venous congestion → relieve dyspnoea, orthopnoea, and PND. Caution: excessive diuresis can ↓preload too much → the already underfilled LV gets even less blood → ↓CO → hypotension |
| Thiazide diuretics | Inhibit Na⁺/Cl⁻ co-transporter in distal convoluted tubule | Adjunctive to loop diuretics for diuretic resistance |
| Aldosterone antagonists (spironolactone) | Block mineralocorticoid receptors in collecting duct → ↓Na⁺ reabsorption and ↓K⁺ excretion | Potassium-sparing effect helpful when using loop diuretics. Also counteracts secondary hyperaldosteronism from low CO state |
Caution with Diuretics in MS
In MS, unlike in heart failure from LV systolic dysfunction, excessive preload reduction is dangerous. The stenotic valve requires a certain minimum LA pressure to maintain forward flow. Over-diuresis → ↓LA filling → ↓transmitral flow → ↓LV filling → ↓CO → hypotension and syncope. Use the lowest effective dose.
AF: rate control [1]. Controlling the ventricular rate is one of the most impactful medical interventions in MS with AF. Here's why:
- In MS, forward flow across the valve depends on diastolic filling time. The faster the heart rate, the shorter diastole becomes. At a heart rate of 150 bpm, diastole may be only 0.15 seconds — far too short for adequate emptying of the LA across a stenotic valve.
- Slowing the heart rate prolongs diastole → more time for blood to flow across the narrowed valve → ↓LA pressure → ↓pulmonary congestion.
| Drug | Mechanism | Notes |
|---|---|---|
| Beta-blockers (e.g. metoprolol, bisoprolol) | Block β₁-adrenergic receptors at the SA and AV node → ↓HR, ↓AV conduction | First-line for rate control. Also blunt the HR response to exercise, preventing exercise-induced tachycardia and decompensation. Caution in decompensated HF |
| Non-dihydropyridine CCBs (diltiazem, verapamil) | Block L-type Ca²⁺ channels at SA and AV node → ↓HR, ↓AV conduction | Alternative to beta-blockers. Avoid in decompensated heart failure (negative inotropy) |
| Digoxin | Enhances vagal tone → ↓AV node conduction → ↓ventricular rate. Also mild positive inotropy | Useful as add-on when beta-blocker or CCB alone is insufficient. Controls resting HR well but less effective during exercise. Narrow therapeutic index — monitor levels (0.5–1.0 ng/mL). Risk of toxicity with hypokalaemia (from diuretics) |
Rate vs Rhythm control in MS with AF? In MS, rhythm control (cardioversion to sinus rhythm) is theoretically attractive because restoring sinus rhythm restores the atrial kick, which is very important for LV filling across a stenotic valve. However, in practice, AF tends to recur in MS because the LA remains dilated (the substrate persists). Rhythm control may be attempted with amiodarone or electrical cardioversion, especially if AF is new-onset and the LA is not massively dilated. Long-term, most patients with chronic MS and AF end up on rate control + anticoagulation.
This is critically important. MS with AF carries one of the highest risks of thromboembolism of any cardiac condition.
| Indication for Anticoagulation | Rationale |
|---|---|
| MS with any AF (paroxysmal, persistent, or permanent) | AF → loss of organised atrial contraction → stasis in the dilated LA → thrombus formation → systemic embolisation (stroke, mesenteric ischaemia, limb ischaemia) [2] |
| MS with prior systemic embolism | Already demonstrated tendency to embolise; high recurrence risk |
| MS with LA thrombus | Direct evidence of thrombus — highest risk |
| MS in sinus rhythm with large LA (> 55 mm) or spontaneous echo contrast ("smoke") | Stasis despite sinus rhythm → thrombogenic milieu |
Drug of choice: WARFARIN (target INR 2.0–3.0)
Why Warfarin and NOT a DOAC?
This is a crucial point that examiners love. MS (particularly rheumatic MS) with AF is one of the few indications where warfarin remains the drug of choice over DOACs (direct oral anticoagulants like rivaroxaban, apixaban, dabigatran). The RE-ALIGN trial demonstrated that dabigatran was inferior to warfarin in patients with mechanical heart valves (more thromboembolic events and bleeding). Current guidelines (2020/2021 ACC/AHA, 2024 ESC) classify MS with AF as "valvular AF" — a category for which DOACs are NOT recommended. Warfarin is the standard [2].
Since RHD is the cause in 95% of cases, preventing recurrent rheumatic fever episodes is essential — each episode worsens valve damage.
| Regimen | Details |
|---|---|
| IM benzathine penicillin G | 1.2 million units IM every 4 weeks [3]. This is the mainstay of secondary prophylaxis |
| Duration | Until age 21 years OR for 5 years after the last episode, whichever is LONGER [3]. If there is carditis with residual valve disease, prophylaxis should continue for at least 10 years or until age 40 (some guidelines say lifelong if severe valve disease) |
| Penicillin-allergic patients | Erythromycin 250 mg BD |
- Routine antibiotic prophylaxis is NOT recommended for native valve MS [3].
- Prophylaxis is indicated only for high-risk groups (prosthetic valves, previous IE, unrepaired cyanotic CHD) undergoing dental procedures [3].
- If the patient has had a mitral valve replacement, they fall into the high-risk category → prophylaxis required.
Remember, acute decompensation of MS is often precipitated by reversible factors:
| Factor | Management |
|---|---|
| AF with rapid ventricular response | Rate control as above |
| Infection/fever | Appropriate antimicrobials, antipyretics (fever ↑HR → ↑transmitral gradient) |
| Anaemia | Transfusion or iron supplementation (anaemia → ↑CO to compensate → ↑gradient) |
| Hyperthyroidism | Antithyroid drugs (hyperthyroidism → ↑HR + ↑CO → decompensation) |
| Pregnancy | Careful haemodynamic management; beta-blocker for rate control; diuretics cautiously; PTMC can be performed during pregnancy if severe MS decompensates |
2. Interventional Therapy
2.1 Percutaneous Transvenous Mitral Commissurotomy (PTMC) / Percutaneous Mitral Balloon Valvuloplasty (PMBV) [1][2]
These terms are used interchangeably. The name tells you the procedure: "percutaneous" = through the skin (no open surgery), "transvenous" = via the venous system, "mitral" = mitral valve, "commissurotomy" = splitting open the fused commissures.
Procedure: A balloon catheter (usually the Inoue balloon) is advanced via the femoral vein → inferior vena cava → right atrium → transseptal puncture through the interatrial septum → left atrium → across the stenotic mitral valve. The balloon is inflated to split the fused commissures, increasing the effective valve area [2].
| Indication | Details |
|---|---|
| Symptomatic severe MS (MVA ≤ 1.5 cm²) | The primary indication. Patient has symptoms (NYHA ≥ II) attributable to MS AND valve morphology is favourable [2] |
| Asymptomatic very severe MS (MVA ≤ 1.0 cm²) | Even without symptoms, the risk of decompensation is high enough to warrant intervention [2] |
| Symptomatic MS with pHTN | PA systolic pressure > 50 mmHg at rest or > 60 mmHg with exercise |
| MS with new-onset AF | AF is a sign of advancing disease and is associated with acute decompensation |
All THREE must be met:
| Prerequisite | Rationale |
|---|---|
| Favourable valve morphology (Wilkins score ≤ 8) [2] | Higher scores indicate immobile, thickened, calcified valves with subvalvular disease → poor commissural splitting, higher risk of iatrogenic MR |
| No moderate-to-severe MR [1] | The balloon inflation can worsen MR by tearing a leaflet or further disrupting the subvalvular apparatus. Starting with significant MR makes this risk unacceptable |
| No LAA thrombus [1] | The catheter passes through the LA. A pre-existing LAA thrombus could be dislodged during the procedure → stroke or systemic embolism. Must be excluded by TOE pre-procedurally |
| Contraindication | Reason |
|---|---|
| Moderate-to-severe MR [1] | Risk of worsening MR to catastrophic levels |
| LAA thrombus [1] | Risk of procedural embolism |
| Calcified valve (Wilkins > 8) [1] | Poor result expected; high risk of complications; no normal tissue to work with [4] |
| Concomitant severe AS or severe AR | Need surgical approach to address multiple valve lesions |
| Severe bicommissural calcification | Even with Wilkins ≤ 8, if both commissures are heavily calcified, commissural splitting is unlikely |
| Complication | Incidence | Mechanism |
|---|---|---|
| Residual ASD (iatrogenic) | ~5% [2] | The transseptal puncture creates a hole in the interatrial septum. Usually small and closes spontaneously. Haemodynamically significant ASDs are rare |
| Periprocedural embolism | ~1–2% [2] | Despite TOE screening, small thrombi may be dislodged. Also risk of air embolism |
| Iatrogenic MR | ~2–10% [2] | Balloon inflation can tear a leaflet, rupture chordae, or split the valve asymmetrically → MR. Severe MR may require emergent surgery |
| Cardiac tamponade | < 1% | Perforation during transseptal puncture or by the catheter/balloon |
| Restenosis | 10–20% at 10 years | Gradual re-fusion of commissures, especially in rheumatic disease |
- Immediate success rate: 85–95% (increase in MVA by ≥50% to > 1.5 cm²)
- Long-term results: 10-year freedom from restenosis or need for surgery ~50–70% with favourable morphology
- Compared to open commissurotomy: similar haemodynamic results with lower morbidity and shorter recovery
2.2 Surgical Options
When valve disease is not repairable... most mitral stenosis — no normal tissue to repair [4]. This is the fundamental surgical reality of MS: rheumatic disease destroys the valve so completely that repair is rarely possible. This contrasts with MR, where repair is often preferred over replacement.
| Aspect | Details |
|---|---|
| Procedure | Open-heart surgery via median sternotomy on cardiopulmonary bypass. The surgeon directly visualises the mitral valve and uses a scalpel to incise the fused commissures under direct vision. Can also resect subvalvular adhesions and debulk calcium |
| Indication | Severe symptomatic MS not suitable for PTMC (e.g. failed PTMC, borderline morphology where an experienced surgeon feels repair is possible, or when concomitant procedures are needed) [2]. Also for non-rheumatic (calcific, congenital) MS where repair may still be possible [2] |
| Advantage over PTMC | Direct visualisation → can address subvalvular disease, remove calcium, excise LAA (reducing thromboembolic risk) |
| Disadvantage | Requires open-heart surgery with sternotomy, cardiopulmonary bypass, and the associated risks |
This is the definitive treatment for most cases of severe MS when PTMC is not feasible.
Procedure: The diseased native mitral valve is excised (including leaflets, chordae, and sometimes papillary muscle tips) and replaced with a prosthetic valve.
| Aspect | Mechanical Valve | Bioprosthetic Valve |
|---|---|---|
| Material | Pyrolytic carbon (e.g. St Jude, On-X) | Porcine valve or bovine pericardial tissue (e.g. Carpentier-Edwards, Hancock) |
| Durability | 20–30+ years (essentially lifelong) | 10–20 years (structural deterioration over time — earlier in younger patients due to more active immune system and higher cardiac output) |
| Anticoagulation | Lifelong warfarin required (target INR 2.5–3.5 for mitral position) | Only warfarin for 3–6 months post-op, then aspirin alone (unless other indication for anticoagulation, e.g. AF) |
| Preferred in | Younger patients (< 50–65 years) who can tolerate lifelong anticoagulation and want to avoid reoperation | Older patients (> 65–70 years), patients with contraindications to anticoagulation, women planning pregnancy (warfarin is teratogenic) |
| Risks | Thromboembolism if INR subtherapeutic, bleeding if INR supratherapeutic, mechanical haemolysis, pannus formation | Structural valve deterioration → need for redo surgery, but lower thromboembolic risk |
The choice of type of prosthetic heart valve should be a shared decision-making process that accounts for the patient's values and preferences and includes discussion of the indications for and risks of anticoagulant therapy and the potential need for and risk associated with reintervention [6].
Indicated for valvular replacement [1]:
| Indication | Rationale |
|---|---|
| Pulmonary hypertension [1] | sPAP > 50 mmHg indicates haemodynamically significant MS with downstream consequences |
| Pulmonary congestion [1] | Persistent symptoms despite medical therapy |
| Haemoptysis [1] | Ruptured bronchial veins from pulmonary venous congestion — risk of massive haemoptysis |
| Recurrent embolic events despite anticoagulation [1] | If a patient on therapeutic warfarin still has embolic events, the valve must be addressed |
| Severe symptomatic MS not suitable for PTMC | When valve morphology precludes PTMC (Wilkins > 8, severe calcification, significant MR) [2] |
| Previously failed PTMC [2] | Restenosis or inadequate result after PTMC |
| Concomitant cardiothoracic surgery [2] | If the patient needs CABG or other valve surgery, MVR can be performed at the same operation |
| Aspect | Details |
|---|---|
| Approach | Median sternotomy (majority) or robotic-assisted minimally invasive (available at QMH) [2] |
| Sternotomy considerations | Takes ~10 weeks for bone to heal → no weight-bearing exercise during this period. Larger wound, risk of sternal wound infection [2] |
| Operative mortality | 1–5% [2] |
| Morbidity | ~5% [2] |
| Recovery | Progressive ↓symptoms and ↑heart function over 3 months after OT [2] |
| Complications | General: CVA, severe infection, bleeding, multi-organ failure [2]. Specific: heart block, heart failure, perioperative MI [2] |
Mechanical vs Bioprosthetic — The Key Trade-Off
The decision comes down to durability vs anticoagulation burden:
- Mechanical valve: lasts forever but requires lifelong warfarin with its attendant bleeding risks, dietary restrictions, drug interactions, and need for regular INR monitoring. Choose for younger patients who can manage anticoagulation.
- Bioprosthetic valve: avoids long-term warfarin but will eventually degenerate and require reoperation. Choose for older patients (lower lifetime risk of needing reoperation) or those who cannot tolerate anticoagulation.
- Shared decision-making between patient and surgeon is emphasised in current guidelines [6].
3. Management of Specific Scenarios
This is a medical emergency. The patient presents acutely with severe dyspnoea, orthopnoea, pink frothy sputum, tachycardia, and hypoxia.
| Step | Action | Rationale |
|---|---|---|
| 1 | Sit patient upright | ↓Venous return to lungs (↓preload) |
| 2 | High-flow O₂ | Correct hypoxia from pulmonary oedema |
| 3 | IV furosemide | ↓Intravascular volume → ↓LA pressure → ↓pulmonary congestion [8] |
| 4 | IV nitrate (GTN infusion) | Venodilation → ↓preload → ↓pulmonary venous pressure. Caution: avoid excessive hypotension [8] |
| 5 | Rate control if AF with rapid ventricular response | Slow HR → prolong diastole → ↓transmitral gradient. IV digoxin, diltiazem, or beta-blocker [9] |
| 6 | Treat precipitant | Identify and treat: infection, anaemia, hyperthyroidism, non-compliance with medications |
| 7 | Non-invasive ventilation (CPAP/BiPAP) if needed | ↑Intrathoracic pressure → ↓preload + ↑oxygenation [8] |
| 8 | Urgent PTMC if refractory | If patient cannot be stabilised medically and valve morphology is favourable |
Key Principle in Acute MS Decompensation
The goal is to reduce heart rate (prolong diastole) and reduce pulmonary congestion (diuretics, nitrates). Do NOT give vasodilators that reduce afterload aggressively (e.g. ACE inhibitors acutely) — in MS, the problem is not LV systolic failure but obstruction to inflow. Reducing afterload won't help and may cause hypotension. This is fundamentally different from the management of acute heart failure from LV dysfunction [8].
| Aspect | Management |
|---|---|
| Rate control | Beta-blockers (metoprolol is preferred — β₁ selective). Avoid atenolol (associated with fetal growth restriction). Digoxin is safe in pregnancy |
| Diuretics | Use cautiously — furosemide if needed but avoid excessive preload reduction |
| Anticoagulation | Warfarin is teratogenic (especially weeks 6–12, causing warfarin embryopathy). Options: subcutaneous LMWH in first trimester → warfarin in 2nd and 3rd trimester → switch to heparin near delivery. This is a complex decision requiring specialist input |
| PTMC during pregnancy | Can be performed if the patient decompensates despite medical therapy. Performed under fluoroscopy with abdominal lead shielding. The alternative (open heart surgery) carries ~20% fetal mortality |
| Delivery | Vaginal delivery is preferred (lower haemodynamic stress than Caesarean section). Epidural anaesthesia is safe. Avoid excessive fluid loading |
| Severity | Follow-up Interval | What to Monitor |
|---|---|---|
| Mild (MVA > 1.5 cm²) | Echo every 3–5 years | Symptoms, valve area progression, rhythm |
| Moderate (MVA 1.0–1.5 cm²) | Echo every 1–2 years | As above + PA pressure, exercise tolerance |
| Severe (MVA < 1.0 cm²), asymptomatic | Echo every 6–12 months | As above + consider exercise echo to unmask symptoms; refer for intervention if MVA ≤ 1.0 cm² with exercise-induced pHTN |
| Clinical Scenario | Management |
|---|---|
| Mild MS, asymptomatic | Surveillance (echo every 3–5 years), secondary RHD prophylaxis, lifestyle advice |
| Moderate MS, asymptomatic | Closer surveillance (echo every 1–2 years), secondary prophylaxis, treat AF if it develops |
| Severe MS, symptomatic, favourable morphology | PTMC [1][2] |
| Severe MS, symptomatic, unfavourable morphology | Surgical commissurotomy or MVR [1][2] |
| Severe MS, asymptomatic, MVA ≤ 1.0 cm² | Consider PTMC if favourable morphology [2] |
| MS with AF | Rate control + anticoagulation (warfarin, INR 2.0–3.0) [1] |
| MS with prior embolism | Warfarin regardless of rhythm |
| Acute decompensation | IV diuretics, rate control, treat precipitant, urgent PTMC if refractory |
| MS in pregnancy | Beta-blocker, cautious diuretics, careful anticoagulation, PTMC if decompensating |
| Post-MVR | Lifelong warfarin (mechanical) or 3–6 months warfarin (bioprosthetic), IE prophylaxis for dental procedures |
High Yield Summary
No medication can fix a stenotic valve. Indication for surgery: severe valve problem with symptoms or ventricular dysfunction [6].
Medical therapy (palliative):
- Diuretics for pulmonary congestion (cautious — avoid excessive preload reduction)
- Rate control for AF: beta-blockers, non-DHP CCBs, digoxin [1]
- Anticoagulation (warfarin, NOT DOACs): for MS with AF, prior embolism, or LA thrombus [1][2]
- Secondary RHD prophylaxis: IM benzathine penicillin G every 4 weeks [3]
Interventional therapy:
- PTMC (first-line) for severe symptomatic MS with favourable morphology (Wilkins ≤ 8), no mod-severe MR, no LAA thrombus [1][2]
- C/I for PTMC: moderate-severe MR, LAA thrombus, calcified valve [1]
- Surgical MVR when PTMC not feasible: most MS cannot be repaired — no normal tissue to repair [4]
MVR indications: Pulmonary hypertension, pulmonary congestion, haemoptysis, recurrent embolic events despite anticoagulation [1]
Prosthetic valve choice: shared decision-making — mechanical (lifelong warfarin, longer durability) vs bioprosthetic (limited durability, no long-term anticoagulation) [6]
Surgical outcomes: mortality 1–5%, morbidity ~5%, progressive improvement over 3 months [2]
Active Recall - Management of Mitral Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (Cardiology section, pp. 35–37) [2] Senior notes: Ryan Ho Cardiology.pdf (pp. 152–155, Mitral Valve Diseases — Medical and Surgical Treatment) [3] Senior notes: Maksim Medicine Notes.pdf (Rheumatic Heart Disease, p. 38; IE prophylaxis, p. 39) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p. 56 — "Most mitral stenosis — no normal tissue to repair") [6] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (pp. 36, 70 — Indications for surgery, shared decision-making for prosthetic valve choice) [8] Senior notes: Ryan Ho Fundamentals.pdf (pp. 217–219 — Acute heart failure management) [9] Senior notes: Ryan Ho Critical Care.pdf (p. 39 — Management of symptomatic tachyarrhythmia)
Complications of Mitral Stenosis
Every complication of MS can be traced back to the single core problem: a narrowed mitral valve orifice obstructing diastolic flow from LA to LV. This creates upstream pressure overload (LA → pulmonary vasculature → right heart) and downstream low flow (reduced LV filling → reduced CO). Understanding this cascade means you can predict and explain every complication from first principles.
Atrial fibrillation occurs in ~45% of MS patients [2] and is one of the most common and clinically significant complications.
Pathophysiology (from first principles):
- Chronic pressure overload → LA dilatation → stretching of atrial myocytes → disruption of normal electrical conduction pathways → formation of multiple re-entrant circuits → AF.
- Additionally, rheumatic inflammation causes atrial fibrosis, which further disrupts conduction and creates a substrate for AF maintenance even after the initial trigger resolves.
- The larger the LA, the more likely AF is to develop and the harder it is to cardiovert back to sinus rhythm.
Why AF is so dangerous in MS:
- Loss of atrial kick: In MS, atrial contraction provides a critical final "push" of blood across the stenotic valve, contributing 15–25% of LV filling. AF eliminates this organised contraction → acute reduction in LV filling → ↑LA pressure → pulmonary congestion [2].
- Rapid ventricular response: The uncontrolled ventricular rate shortens diastole → less time for blood to flow across the narrowed valve → further ↑transmitral gradient → further ↑LA pressure.
- Occurrence of AF is associated with acute cardiac decompensation [2] — patients who were previously compensated may present with flash pulmonary oedema when AF develops.
Management: Rate control (beta-blockers, non-DHP CCBs, digoxin) + anticoagulation (warfarin) [1]. Consider cardioversion if new-onset and LA is not massively dilated.
AF in MS = Medical Emergency
New-onset AF in a patient with moderate-severe MS should be treated urgently. The combination of loss of atrial kick AND rapid ventricular rate can precipitate acute pulmonary oedema within hours. Urgent rate control is the priority — slow the heart rate to prolong diastole and allow more time for transmitral flow.
Embolization: enlarged LA → stasis [2].
This is one of the most feared complications because it can cause devastating stroke.
Pathophysiology:
- LA dilatation → sluggish blood flow, particularly in the left atrial appendage (LAA), which is a blind-ended pouch with trabeculated walls → ideal conditions for thrombus formation (Virchow's triad: stasis, endothelial injury from rheumatic inflammation, hypercoagulability from chronic inflammation).
- AF compounds this: the fibrillating atrium has no effective contraction → complete stasis → thrombus formation.
- Thrombus fragments can detach and embolise to any systemic arterial territory.
Target organs of embolisation:
| Territory | Clinical Consequence |
|---|---|
| Cerebral arteries | Embolic stroke — the most devastating complication. Features suggestive of cardioembolic stroke: non-progressive onset, non-lacunar pattern with cortical deficits (hemianopia, aphasia, apraxia), multiple territories, haemorrhagic transformation on CT, presence of cardioembolic source with no atherosclerosis on angiography [10] |
| Mesenteric arteries | Acute mesenteric ischaemia → severe abdominal pain, bloody diarrhoea, bowel infarction. Surgical emergency |
| Renal arteries | Renal infarction → flank pain, haematuria, elevated LDH |
| Peripheral arteries (limb) | Acute limb ischaemia → the 6 P's (pain, pallor, pulselessness, paraesthesia, paralysis, perishingly cold) |
| Splenic artery | Splenic infarction → left upper quadrant pain |
Risk factors for embolism in MS:
- AF (strongest risk factor)
- Large LA (> 55 mm)
- Spontaneous echo contrast ("smoke" on echo — indicates stasis)
- Previous embolic event
- Low cardiac output
- Advanced age
Prevention: Anticoagulation with warfarin (INR 2.0–3.0) is mandatory for all MS patients with AF, prior embolism, or LA thrombus [1][2]. Recurrent embolic events despite anticoagulation is an indication for mitral valve replacement [1].
Cardiac evaluation for cardioembolic causes in stroke work-up includes Echo (TTE/TEE) for valvular heart disease and ECG ± Holter for AF [10]. MS is a classic cardioembolic source.
Pathophysiology:
- ↑LA pressure → transmitted backwards to pulmonary veins (no valves between LA and pulmonary veins) → ↑pulmonary capillary hydrostatic pressure.
- When pulmonary capillary hydrostatic pressure exceeds plasma oncotic pressure (~25 mmHg), fluid transudates from the capillaries into the pulmonary interstitium and then into the alveoli → pulmonary oedema.
- Chronic, mild elevation → interstitial oedema only → dyspnoea on exertion, Kerley B lines on CXR, upper lobe pulmonary venous distension [2].
- Acute, severe elevation (e.g. from new-onset AF, tachycardia, exercise) → frank alveolar flooding → acute pulmonary oedema with pink frothy sputum, severe dyspnoea, hypoxia → life-threatening.
Clinical presentation: SOB on exertion → orthopnoea → PND → acute pulmonary oedema (in order of increasing severity) [2].
Haemoptysis: ruptured bronchial veins due to pulmonary congestion [1][2].
Pathophysiology (from first principles):
- The bronchial veins drain into the pulmonary veins. When pulmonary venous pressure is chronically elevated, this back-pressure is transmitted into the bronchial venous plexus.
- These thin-walled bronchial veins become chronically engorged and dilated (similar to oesophageal varices in portal hypertension, but in the lungs).
- They can rupture spontaneously, especially with coughing or increased intrathoracic pressure → haemoptysis.
Different mechanisms of haemoptysis in MS:
| Mechanism | Details |
|---|---|
| Bronchial vein rupture | The classic mechanism in MS. Frank haemoptysis, can occasionally be massive and life-threatening |
| Pulmonary oedema | Pink frothy sputum — not true haemoptysis but blood-tinged oedema fluid. Occurs in acute decompensation |
| Pulmonary infarction | If thromboembolism occurs (from LA thrombus → pulmonary embolism, or paradoxical embolism), the infarcted lung tissue produces haemoptysis with pleuritic chest pain |
Clinical significance: Haemoptysis is an indication for mitral valve replacement [1] — it signifies severe pulmonary venous hypertension and risk of life-threatening bleeding.
Note: In the work-up of haemoptysis, mitral stenosis must always be considered as a possible cause [11]. This is why a cardiovascular examination is essential in any patient presenting with haemoptysis.
Pulmonary hypertension due to passive (back-transmission of ↑LAP) and reactive (late vascular remodelling of pulmonary arterioles with chronic pHTN) components [2].
This is a major complication that fundamentally alters the natural history of MS.
Two components (reviewed again for completeness):
| Component | Mechanism | Reversibility |
|---|---|---|
| Passive | Direct back-transmission of elevated LA pressure into pulmonary vasculature. Proportional to degree of LA hypertension | Reversible — improves immediately after successful PTMC or MVR when LA pressure drops |
| Reactive | Chronic pulmonary venous hypertension triggers arteriolar vasoconstriction (neurohormonal, endothelin) → followed by vascular remodelling (medial hypertrophy, intimal fibrosis of pulmonary arterioles) | Partially reversible early on (vasoconstriction component responds to treatment). Fixed and irreversible once structural remodelling is established (the arterioles are physically thickened and cannot dilate) |
Clinical significance:
- 10-year survival becomes < 3 years once pHTN develops [2].
- Pulmonary hypertension is an indication for intervention (PTMC or MVR) [1] — you want to intervene before the reactive component becomes fixed and irreversible.
- Severe pHTN increases operative risk for MVR significantly, particularly if PVR is very high (> 6 Wood units) and fixed.
Auscultatory sign: Loud P2 (forceful closure of pulmonary valve from high PA pressure), Graham Steell murmur (PR murmur, associated with loud P2, indicating severe MS [1]).
6. Compression Syndromes from LA Enlargement
As the LA progressively dilates, it can compress adjacent mediastinal structures:
- Mechanism: LA enlargement → compression of the left recurrent laryngeal nerve (RLN) → hoarseness of voice [1].
- Anatomy: The left RLN loops under the aortic arch and ascends in the tracheo-oesophageal groove, passing between the aorta and the pulmonary artery, directly adjacent to the LA. A massively dilated LA (or a dilated pulmonary artery from pHTN) can compress this nerve.
- Consequence: Left vocal cord paralysis → hoarseness, weak voice, sometimes aspiration risk.
- Clinical significance: Indicates massive LA dilatation — a sign of advanced, severe MS.
- Mechanism: The oesophagus passes directly behind the LA. Massive LA dilatation compresses the oesophagus posteriorly → difficulty swallowing, especially solids [2].
- Less common than Ortner syndrome but an important clue on barium swallow (posterior displacement of the oesophagus).
Chronic ↑pulmonary venous pressure → ↑RV load → right heart failure [2].
Pathophysiology:
- The RV is a thin-walled, crescent-shaped chamber designed for a low-pressure system (normal PA systolic pressure ~25 mmHg).
- Chronic pulmonary hypertension from MS imposes a pressure overload on the RV.
- Initially, the RV compensates with concentric hypertrophy (manifesting as a left parasternal heave).
- Eventually, the RV decompensates → RV dilatation → ↓RV contractility → ↓RV output → ↑systemic venous pressure.
Clinical manifestations of right heart failure:
| Sign/Symptom | Mechanism |
|---|---|
| Elevated JVP | ↑RA pressure transmitted to jugular veins |
| Hepatomegaly (tender, pulsatile) | Systemic venous congestion → blood backs up into hepatic veins → liver swells. If functional TR develops, the liver pulsates with each systolic regurgitant wave |
| Ascites | Chronic hepatic congestion → ↑hydrostatic pressure in hepatic sinusoids → transudation into peritoneal cavity. Also ↓albumin synthesis from congestive hepatopathy contributes |
| Peripheral oedema | ↑systemic venous pressure → ↑capillary hydrostatic pressure in dependent areas → fluid transudation into interstitial tissue |
| Facial congestion / mitral facies | Malar flush: low CO results in poor facial skin perfusion → release of vasodilators by skin tissue → cutaneous vasodilation on cheeks [5]. Combined with CO₂ retention from pulmonary congestion → bluish-red discolouration |
Paradox of Right Heart Failure in MS
Interestingly, when severe RV failure develops in MS, the patient's pulmonary congestion may actually improve — because the failing RV cannot pump enough blood through the pulmonary vasculature to cause congestion. The patient "trades" pulmonary symptoms (SOB, orthopnoea) for systemic congestion symptoms (ascites, oedema, hepatomegaly). This can be misleading — the patient seems to "improve" from a pulmonary standpoint while actually deteriorating overall.
8. Functional Tricuspid Regurgitation and Graham Steell Murmur
- Mechanism: RV pressure overload → RV dilatation → tricuspid annulus stretches → tricuspid valve leaflets can no longer coapt properly → functional (secondary) tricuspid regurgitation [2].
- Clinical sign: Pansystolic murmur at the LLSB that increases with inspiration (Carvallo's sign) [1].
- Consequence: Further worsens right heart failure (the RV now has both pressure overload from pHTN AND volume overload from regurgitation → accelerated RV failure).
- Mechanism: Severe pulmonary hypertension → dilatation of the pulmonary valve annulus → pulmonary valve leaflets can no longer coapt → functional pulmonary regurgitation (PR).
- Auscultatory finding: PR murmur: early diastolic decrescendo murmur at the left 2nd–3rd intercostal space, associated with loud P2, indicating severe MS [1].
- Clinical significance: The presence of a Graham Steell murmur tells you that the patient has severe, long-standing pulmonary hypertension. It is a marker of advanced disease.
Pathophysiology:
- Chronic right heart failure → chronic hepatic venous congestion → centrilobular necrosis (zone 3 hepatocytes, which are furthest from the hepatic arterial supply, are most vulnerable to hypoxia and congestion).
- Over time, repeated episodes of congestion and necrosis → fibrosis → cardiac cirrhosis.
Clinical features:
- Hepatomegaly (tender initially, becomes firm and non-tender as fibrosis develops)
- Elevated transaminases (ALT, AST) during acute congestion episodes
- Elevated bilirubin → jaundice in severe cases
- Low albumin → contributes to ascites and oedema
- Prolonged PT/INR → coagulopathy
- In very advanced cases → portal hypertension from cardiac cirrhosis → oesophageal varices, splenomegaly
Cardiac cause of jaundice includes severe congestive HF leading to hepatic congestion or cardiac cirrhosis [5].
Pathophysiology:
- The turbulent blood flow across the stenotic mitral valve damages the valvular endothelium → creates a nidus for bacterial adhesion → vegetations form.
- Rheumatic valves are particularly susceptible because they are already abnormal (thickened, scarred, calcified), providing an irregular surface for platelet-fibrin deposition and subsequent bacterial colonisation.
Clinical features: Fever, new/changing murmur, embolic phenomena (splinter haemorrhages, Osler's nodes, Janeway lesions, Roth spots), positive blood cultures [3].
Risk: MS is a risk factor for subacute infective endocarditis (caused by less virulent organisms like Strep viridans that tend to infect abnormal valves) [3].
Prevention: Routine antibiotic prophylaxis is NOT recommended for native valve MS. Only indicated for high-risk groups (prosthetic valves, previous IE, unrepaired cyanotic CHD) undergoing dental procedures [3].
Concomitant MR: significantly calcified valve impairing closing [1].
Pathophysiology:
- As rheumatic disease progresses, the valve becomes not only stenotic but also increasingly calcified and rigid.
- A severely calcified valve may not only fail to open adequately (stenosis) but also fail to close properly → mixed mitral valve disease (MS + MR).
- The MR adds a volume overload component to the already pressure-overloaded LA → accelerates LA dilatation, AF, and pulmonary congestion.
- Mixed lesions are particularly challenging because the haemodynamic consequences compound each other.
Clinical implication: Moderate-to-severe MR is a contraindication for PTMC [1] because balloon dilation may worsen the MR catastrophically.
12. Complications of Treatment
| Complication | Mechanism |
|---|---|
| Residual ASD (~5%) | Transseptal puncture creates an iatrogenic hole in the interatrial septum |
| Iatrogenic MR | Balloon inflation tears leaflet or disrupts subvalvular apparatus |
| Periprocedural embolism | Dislodgement of thrombus or air embolism |
| Cardiac tamponade | Perforation during transseptal puncture |
| Complication | Mechanism |
|---|---|
| CVA | Perioperative embolism (air, thrombus, calcific debris) |
| Heart block | Surgical damage to the AV node or His bundle (which lies close to the mitral annulus) |
| Heart failure | Perioperative myocardial injury, loss of subvalvular apparatus (if chordae are excised during MVR, LV geometry is altered → impaired LV function) |
| Perioperative MI | Coronary embolism or air lock, especially in patients with pre-existing CAD |
| Severe infection | Sternal wound infection, mediastinitis (especially after median sternotomy), prosthetic valve endocarditis |
| Bleeding | Cardiopulmonary bypass requires heparinisation; also inherent surgical bleeding risk |
| Prosthetic valve complications | Thrombosis (if anticoagulation inadequate), pannus formation, structural valve deterioration (bioprosthetic), mechanical haemolysis (mechanical valves) |
| Overwarfarinisation [2] | The majority of MS patients with AF are on warfarin → risk of bleeding complications (intracranial haemorrhage, GI bleeding, etc.) if INR is supratherapeutic |
| Upstream Mechanism | Complication |
|---|---|
| LA pressure overload → LA dilatation | Atrial fibrillation, thromboembolism (stroke), Ortner syndrome, dysphagia, concomitant MR |
| Pulmonary venous congestion | Pulmonary oedema (acute and chronic), haemoptysis (bronchial vein rupture) |
| Pulmonary hypertension | RV failure, functional TR, Graham Steell murmur (functional PR) |
| Right heart failure | Systemic venous congestion (JVP↑, hepatomegaly, ascites, oedema), congestive hepatopathy → cardiac cirrhosis |
| Low forward cardiac output | Fatigue, exercise intolerance, mitral facies |
| Abnormal valve surface | Infective endocarditis |
| Treatment-related | PTMC complications (ASD, iatrogenic MR, embolism), surgical complications (CVA, heart block, HF, MI, infection, bleeding), anticoagulation complications (over-warfarinisation) |
High Yield Summary
Complications of MS all trace back to: ↑LA pressure → LA dilatation → pulmonary venous congestion → pHTN → RV failure.
Most common and important complications:
- AF (~45%) → acute decompensation + thromboembolism risk [2]
- Systemic thromboembolism (stroke) → requires warfarin anticoagulation [1][2]
- Pulmonary oedema → dyspnoea, orthopnoea, PND → flash pulmonary oedema if acutely decompensated
- Haemoptysis → bronchial vein rupture from pulmonary venous congestion; indication for MVR [1]
- Pulmonary hypertension → passive + reactive components; < 3-year survival once established [2]; indication for intervention [1]
- Ortner syndrome → LA compresses left RLN → hoarseness [1]
- Right heart failure → hepatomegaly, ascites, oedema, functional TR
- Graham Steell murmur → functional PR from severe pHTN [1]
- Congestive hepatopathy → may progress to cardiac cirrhosis
- Infective endocarditis → abnormal valve surface predisposes
- Concomitant MR → calcified valve fails to close; CI to PTMC [1]
- Treatment complications → PTMC: residual ASD (5%), iatrogenic MR, embolism [2]. Surgery: CVA, heart block, HF, MI, infection, bleeding [2]
Active Recall - Complications of Mitral Stenosis
References
[1] Senior notes: Maksim Medicine Notes.pdf (Cardiology section, pp. 35–37) [2] Senior notes: Ryan Ho Cardiology.pdf (pp. 152–155, Mitral Valve Diseases) [3] Senior notes: Maksim Medicine Notes.pdf (Rheumatic Heart Disease p. 38; Infective Endocarditis p. 39) [4] Lecture slides: Cardiac Surgery Tutorial_Prof. D Chan.pdf (p. 56 — "Most mitral stenosis — no normal tissue to repair") [5] Senior notes: Ryan Ho Fundamentals.pdf (pp. 13, 22 — Mitral facies, cardiac causes of jaundice) [10] Senior notes: Ryan Ho Neurology.pdf (pp. 75, 80 — Risk factors for stroke, features of embolic stroke, cardiac evaluation) [11] Senior notes: Ryan Ho Respiratory.pdf (p. 23 — Haemoptysis approach, mitral stenosis as a cause)
Aortic Regurgitation
Aortic regurgitation is the backflow of blood from the aorta into the left ventricle during diastole due to incompetent closure of the aortic valve, leading to left ventricular volume overload.
Mitral Regurgitation
Mitral regurgitation is the backward leakage of blood from the left ventricle into the left atrium during systole due to incompetent closure of the mitral valve.