Overview

Mitral regurgitation (MR), which is also known as mitral insufficiency, is a common heart valve disorder. When MR is present, blood leaks backwards through the mitral valve when the heart contracts. This reduces the amount of blood that is pumped out to the body. Patients with acute mitral regurgitation (MR) are often gravely ill with significant haemodynamic abnormalities that require urgent medical and usually surgical treatment.

Heart Valve

The heart has 4 valves:

• Aortic valve
• Pulmonary valve
• Tricuspid valve
• Mitral valve (bicuspid valve)

The Mitral and tricuspid valves are atrioventricular valves meaning they allow blood to move from the atrium to the ventricles of the heart. This occurs with ventricular diastole.

The aortic and pulmonary valve are tricuspid valves which when open allow blood to move to the aorta and pulmonary system respectively. This occurs during ventricular systole when the heart contracts.

Surface anatomy of the heart valves

All of the heart valves except the mitral valve are usually tricuspid. However, there can be congenital bicuspid valves which can predispose one to valvular disease later on. The heart valves can be heard most prominent in the following regions of the chest

• Aortic valve – Right 2nd intercostal space parasternal
• Pulmonary valve – Left 2nd intercostal space parasternal
• Tricuspid valve – Left 4th intercostal space parasternal
• Mitral valve – Left 5 intercostal space mid-clavicular (below the nipple)

Aetiology and Risk Factors

Aetiology

There are three basic mechanisms of Mitral regurgitation:

1. Ruptured mitral chordae tendineae (flail leaflet) due to myxomatous disease (mitral valve prolapse), infective endocarditis, trauma, rheumatic heart disease (acute rheumatic fever or chronic rheumatic mitral valve disease), or spontaneous rupture.
2. Papillary muscle rupture due to acute myocardial infarction or trauma or papillary muscle displacement due to myocardial infarction or ischemia.
3. Induction of MR in the setting of dynamic left ventricular outflow obstruction. This complication has been observed in patients with left ventricular hypertrophy (including patients with hypertrophic cardiomyopathy), as well as in patients with myocardial infarction or Takotsubo cardiomyopathy

Pathophysiology

Primary causes abnormality of dysfunction of any component of the mitral valve apparatus

Secondary causes (functional MR) abnormality of dysfunction of the left ventricle

• Coronary heart disease
• Cardiomyopathy

Pathophysiology Acute MR

• Primary and secondary causes → weak mitral valve causing regurgitation → ↑preload and ↓afterload → ↑strokevolume
• ↑stroke volume → blood flows toe right atrium through incompetent mitral valve → pulmonary veins → pulmonary oedema

Pathophysiology Chronic MR

• Compensated Overtime the left ventricle will compensate for the↑preload  → Enlargement of left ventricle → Dilated cardiomyopathy (eccentric left ventricular hypertophy)
• Decompensated Overtime the dilated cardiomyopathy gets bad until ejection fraction drops. Low ejection fraction occurs as a result of afterload acess and depressed myocardial contractility.

Clinical Manifestation

Acute MR presents as a cardiac emergency, however chronic MR typically presents with no symptoms until late stage.

• Pulmonary oedema
• Hypotension
• Cardiogenic shock
  • Pallor
  • Diaphoresis
  • Tachycardia
• Signs of right sided heart failure
  • Raised JVP
  • Peripheral oedema
• Sign of AF
  • palpitation

Most people with mitral regurgitation (MR) have no symptoms. People with mild to moderate MR may never develop symptoms or serious complications. A trivial amount of mitral regurgitation (MR) is present in up to 70 percent of adults. Significant (moderate to severe) MR is much less common.

Cardiac Examination

• Holosystolic (Pansystolic murmur) – occurs during systole
• Murmur radiates to axilla

Cardiac Examination includes a murmur heard over the left 5th intercostal space mid-clavicular. The murmurs is a flat continuous murmur which radiates to the axilla. There also tends to be a diminished S1.

Clinical Signs of severity

1. Enlarged left ventricle
2. Pulmonary hypertension
3. Left ventricular failure
4. Third hard sound, S3
5. Soft first heart sound
6. S2 splitting (A2 heard before P2)
7. Small volume pulse

Diagnosis

• Acute Coronary Syndrome
• Mitral stenosis
• Aortic stenosis
• Infective endocarditis
• Atrial Myxoma

Investigations

• Chest X-ray
• Exercise tolerance test
• ECG – detect rhythm disturbances or evidence of coronary heart disease or other conditions that can cause MR. It can also show evidence of other associated cardiac abnormalities.
• Ultrasound – gold standard for diagnosing valvular heart diseases.

Diagnosis

Clinical history and examination findings of MR. Ultrasound finding of mitral valve insufficiency.

Treatment

Acute Mitral Regurgitation

Inoperable patients

• Valvuloplasty
• Annuloplasty

Operable patients

• Valve Replacement (~Ejection Fraction <60)
  • mechanical
  • bioprosthetic

Chronic Mitral Regurgitation

• ACE inhibitor or beta-blocker (Asymptomatic)
• Vasodilators
• Serial echocardiograms for monitoring
• Surgery as above

Complications and Prognosis

Complication

• Atrial fibrillation
• Right axis deviation
• Left ventricular failure (left-sided heart failure)

Mitral Valve Prolapse

Overview Most common congenital valvular lesion. Associated with Marfan’s Syndrome and Ehlor’s Danlos Syndrome.

Clinical Examination

• Mostly asymptomatic
• Palpitations
• Atypical chest pain
• Mid-to late systolic CLICK
  • Due to tensing of the chordae tendinae and prolapse of the leaflet. Late systolic murmur due to associated MR.
• Worsens with valsalva maneuver
• Improves with squatting

Complications

• Serious arrhythmias and sudden death
• CHF
• Endocarditis

References

Best Practice
UptoDate
Oxford Handbook Clinical Medicine