Mitral valve disease

Mitral valve disease refers to abnormalities of the mitral valve.

It includes 3 diseases:

1. Mitral stenosis
2. Mitral regurgitation
3. Mitral valve prolapse

🦴 Anatomy

The mitral valve is also known as the bicuspid valve as it is the only bicuspid valve in the heart. It is an atrioventricular valve located between the left atrium and left ventricle.

It is located behind the 4th intercostal space. It is oriented almost vertically, facing slightly to the right, similar to our tricuspid valve.

We auscultate it over the 5th intercostal space, mid-clavicular line on the left-hand side.

It opens during ventricular diastole to allow blood to flow from the left atrium to ventricle (pre-load). During ventricular systole it closes to prevent back flow of blood to the left atrium, thus enabling it to pass blood to the aorta.

Chordae tendinae are attached to the mitral valve (and tricuspid valve) along with papillary muscles. When the ventricles of the heart contract in ventricular systole, the increased blood pressures in both chambers push the AV valves to close simultaneously, preventing backflow of blood into the atria. Since the blood pressure in atria is much lower than that in the ventricles, the flaps attempt to evert to the low pressure regions. The chordae tendineae prevent this prolapse by becoming tense as the papillary muscles contract, which pulls on the flaps, holding them in closed position.

MITRAL STENOSIS

Mitral stenosis is when the mitral valve cannot fully open during ventricular diastole, thus leading to a lower end-diastolic volume in the left ventricle, and increasing the valvular gradient (difference in pressure between left atrium and left ventricle) and left atrial pressure due to retention of the blood.

Pathophysiology

Our normal mitral valve has an opening of approximately 4cm².

With restriction of the flow, there are 2 main consequences:

1. Increased left atrial pressure ultimately leading to congestion in the lungs.
2. Limiting of cardiac output as the LVEDV is reduced.

It mimics left heart failure despite a normally functioning left ventricle.

Pressure begins to overload and backs up into the right ventricle. Later on, we also get pulmonary vasoconstriction which increases right ventricle pressure. Eventually we get severe pulmonary hypertension.

The most common cause of mitral stenosis is rheumatic heart disease.

Other causes are:

1. Mitral annular calcification
2. Congenital mitral stenosis
3. Mucopolysaccharidosis
4. Carcinoid syndrome
5. SLE and RA

😷 Presentation

Symptoms of mitral stenosis include:

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Auscultation findings:

Mid-diastolic murmur heard best at the apex beat when the patient is lying on their left lateral side. Heard loudest on expiration.

🔍 Investigations

🥇🏆 The first-line and gold standard investigation is transthoracic echocardiogram.

• ECG
• CXR may show evidence of pulmonary oedema and left atrial enlargement. The double density sign over the right heart border is a sign of left atrial enlargement.

🧰 Management

Asymptomatic patients require monitoring via regular echocardiograms.

In patients with associated atrial fibrillation:

Associated atrial fibrillation:

We need to do 2 things: anti-coagulation and rate control:

1. Anti-coagulation
1. Warfarin is still recommended win patients with moderate/severe mitral stenosis.
2. Rate control
1. B-blockers
2. Ivabradine

MITRAL REGURGITATION

Mitral regurgitation is the failure of the mitral valve to close during ventricular systole, thus allowing back flow of blood into the left atrium from the left ventricle during contraction. It is the second most common valve disease after aortic stenosis.

As the degree of regurgitation increases, the oxygen demands may exceed what the heart can supply, leading to a hypertrophic response (left ventricular hypertrophy) → heart failure.

It may occur due to:

1. Post-MI or IHD - if the papillary muscles rupture.
2. Mitral valve prolapse (we will discuss this later)
3. Infective endocarditis
4. Rheumatic heart disease
5. Congenital defects

⚠️ Risk factors

😷 Presentation

It is mostly asymptomatic in mild-moderate mitral regurgitation.

Symptoms, if present, are representative of left ventricular failure, arryhthmias, pulmonary hypertension:

1. Fatigue
2. Dyspnoea
3. Oedema

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Auscultation findings:

• Pansystolic murmur - described as a “blowing” sound. Best heard at the apex, radiating to the axilla.
• Quiet S1 due to incomplete closure of the valve
• Widely split S2 sound in severe mitral regurgitation.
• Displaced, hyperdynamic apex beat

🔍 Investigations

🏆🥇 Transthoracic echocardiography is best to diagnose MR and assess the severity.

• ECG is done for all patients to obtain a baseline ECG. It may show:
• P-mitrale - a bifid P-wave
• Right ventricular hypertrophy
• Right axis deviation

🧰 Management

MITRAL VALVE PROLAPSE

Mitral valve prolapse refers to prolapsing of one or both of the mitral valve leaflets prolapse into the left atrium during ventricular systole.

It is a common disorder, occurring in 5-10% of the population. It rarely results in serious complications but can lead to severe mitral regurgitation, infective endocarditis, and even may cause sudden cardiac death.

It may occur due to chronic mitral regurgitation or may happen acutely with acute prolapse.

Pathophysiology

We can classify MVP as classic/primary or non-classic/secondary. Primary MVP appears to have a familial link but the cause is still unclear.

In primary MVP we see a myxomatous degeneration of the mitral valve. This is characterised by altered collagen synthesis leading to a defective, floppy valve leaflet (most commonly the posterior leaflet).

Secondary mitral valve prolapse is associated with a couple of disorders:

😷 Presentation

Once again, it is very often asymptomatic.

Some symptoms, however, may include:

1. Atypical chest pain
2. Palpitations
3. Dyspnoea
4. Exercise intolerance
5. Dizziness
6. Associate symptoms with primary disorders that cause secondary MVP.

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Auscultation findings:

• Late systolic murmur
• Mid-systolic crisp click - known as “click murmur syndrome”
• Pansystolic murmur

The murmurs are heard at the apex of the hear and are accentuated by standing and also when performing a valsalva maneuver.

🔍 Investigation

🥇 Echocardiography is first-line along with clinical history. It is seen as one or both leaflets sitting >2mm above the annulus on the echocardiogram.

🧰 Management

In asymptomatic patients we can consider anti-coagulation or anti-platelet therapy.

If symptomatic patients the first-line option is lifestyle modification but if there is severe mitral regurgitation then we can consider mitral valve replacement.