Mitral Regurgitation (MR) - Symptoms & Causes

What is mitral regurgitation (MR)?

Mitral regurgitation (MR) is a condition in which the heart's mitral valve does not close tightly, allowing blood to leak backwards into the left atrium when the left ventricle contracts. This reduces the efficiency of the heart’s ability to pump blood to the rest of the body and can lead to symptoms of heart failure if left untreated.

The mitral valve is one of four valves in the heart and plays a crucial role in maintaining the one-way flow of blood. In MR, this flow is disrupted, leading to increased pressure in the lungs and heart over time.

Types of mitral regurgitation (MR)

Mitral regurgitation can be categorised into 2 main types:

• Primary (degenerative) MR
  This form is caused by structural abnormalities of the mitral valve itself. It may result from mitral valve prolapse, ruptured chordae tendineae (supporting strands), or calcification of the valve leaflets.

• Secondary (functional) MR
  This type occurs when the valve is structurally normal but becomes incompetent due to enlargement or dysfunction of the left ventricle. This often arises in the context of heart failure or after a heart attack that weakens the heart muscle.

What are the symptoms of mitral regurgitation (MR)?

The symptoms of MR can vary depending on its severity and whether it develops gradually or suddenly. Common signs and symptoms include:

• Shortness of breath, particularly during exertion or when lying flat
• Fatigue and reduced exercise tolerance
• Palpitations or an irregular heartbeat
• Swollen ankles or feet (oedema)
• A sensation of a rapid or pounding heart
• Cough, particularly at night or when lying down

In some cases, particularly in early or mild MR, patients may remain asymptomatic and the condition may be detected incidentally during a routine examination.

What causes mitral regurgitation (MR)?

Mitral regurgitation can result from a range of underlying conditions. These include:

• Mitral valve prolapse – where the valve leaflets bulge back into the atrium
• Rheumatic heart disease – a complication of untreated streptococcal infections
• Endocarditis – infection of the heart valves
• Heart attacks (myocardial infarctions) – which may damage the muscles supporting the mitral valve
• Cardiomyopathy – weakening or enlargement of the heart muscle
• Congenital heart defects – present from birth
• Age-related degeneration – affecting valve flexibility and strength

What are the complications of mitral regurgitation (MR)?

If left untreated, mitral regurgitation can lead to serious complications such as:

• Heart failure – due to the heart’s inability to maintain adequate circulation
• Atrial fibrillation – a common arrhythmia that increases stroke risk
• Pulmonary hypertension – elevated pressure in the lungs
• Stroke or blood clots – due to abnormal blood flow and rhythm disturbances
• Right-sided heart strain – from long-standing elevated pressure in the pulmonary system