Barlow's syndrome is a relatively common condition in which there is an abnormality of the mitral valve of the heart.


  • Barlow's syndrome is a relatively common condition in which there is an abnormality of the mitral valve of the heart.
  • This can sometimes lead to severe mitral regurgitation, in which blood leaks into the left atrium as a result of the incompetent valve during ventricular contraction.
  • Barlow's syndrome is more common in people who suffer from diseases such as Graves' disease, Marfan's syndrome and rheumatic heart disease.
  • Most people do not suffer from symptoms, but if they do, these may include palpitations, fatigue, dizziness, shortness of breath, chest pain and migraine.
  • Treatment depends on the symptoms.

Alternative names

Barlow's syndrome; floppy-valve syndrome; billowing mitral valve syndrome


Barlow's syndrome is a relatively common condition in which the leaflets of the mitral valve bulge into the left atrium of the heart as the valve closes during ventricular contraction. This abnormality may prevent the valve from closing properly, causing it to leak.

The mitral valve is the heart valve which lies between the two left chambers of the heart – the left atrium on the top and left ventricle below. The leaflets of the valve are the thin strips of tissue which move when the valve closes or opens during contraction and relaxation.


The underlying problem with the valve is a degeneration of the tissue causing the leaflets to become stretched and enlarged. This redundant tissue bulges into the atrium, preventing the valve from closing properly. The exact reason for this tissue change is not known, but it is associated with othe tissue degenerative disorders.

Functional MVP can occur with completely normal valve leaflets: this is found in conditions of abnormal papillary muscle function due to myocardial ischaemia, and in dilated cardiomyopathy. Patients with hypertrophic cardiomyopathy are also at risk.

Who is at risk?

Barlow’s syndrome occurs in 1% to 6% of otherwise normal populations.

People with Graves’ disease, Marfan’s syndrome, Duchenne muscular dystrophy, myotonic dystrophy, sickle cell disease and rheumatic heart disease have a higher incidence of the condition.

Symptoms and signs

Most patients do not experience symptoms. However, when they do the symptoms include:

  • Fatigue
  • Migraine
  • Dizziness
  • Panic attacks
  • Low blood pressure when lying down
  • Shortness of breath
  • Palpitations
  • Chest pain that is not angina

However, these non-specific symptoms are not reliable indicators of the condition.

When the doctor listens to the heart, a murmur may be heard. This is caused by irregular blood flow through the valve. A click may also be heard, thought to be due to the snapping of the anchoring "ropes" - the chordea - as the valve billows and then is suddenly held taut. This is much like the snapping taut of the sails on a boat. These sounds are often transient or absent, and might only be detected by an experienced cardiologist.

If there are problems with the function of the left ventricle, the patient may experience shortness of breath and troublesome irregularities of heart rhythm.

Barlow’s syndrome may result in severe dysfunction of the mitral valve, leading to what is called mitral regurgitation (MR), a leaking, or incompetent valve. Mitral regurgitation means that blood flows back into the left atrium during contraction rather than moving forwards into the aorta as it should do.

About 25% of people with Barlow's syndrome also suffer from lax joints, and a high arched palate in the mouth (these patients may also have a degree of Marfan's syndrome), and other abnormalities of their skeleton such as scoliosis, a funnel chest and a straight back.


Diagnosis is made by:

  • Electrocardiogram (the electrical activity of the heart is recorded), which shows characteristic changes in heart function.
  • Echocardiogram (ultrasound is used to visualise the heart), in which the function of the valve can be seen directly. Two-dimensional echocardiography is particularly useful in identifying the valve leaflet position during heart contraction and relaxation. This is the most useful non-invasive test.


The most important factor is to assess the degree of prolapse, and the degree, if any, of mitral valve regurgitation (leakage).,/p>

In the absence of significant valve dysfunction, symptoms such as dizziness, palpitations and migraine can be treated with appropriate medication. This may include beta-blockers and warfarin. These patients can follow a normal lifestyle with regular moderate exercise. Stimulants, such as excess caffeine, and stress should be avoided.,/p>

A patient who has definite clicks and murmurs when the doctor listens to the heart may need to avoid highly competitive sports.

If mitral regurgitation is present, antibiotics should be taken during dental extractions or other procedures that may lead to the spread of bacteria through the bloodstream. Bacteria may cause an infection of the valve called endocarditis.


The severity of MR determines the degree of its complications. Moderate to severe MR can lead to sudden death, atrial fibrillation, rupture of the chordae, heart failure or infective endocarditis.

About 10% of patients will need to have a valve replacement, especially when cardiac function decreases to 50% or less. Timeous surgery will prevent heart failure. Sudden death is rare.


The degeneration of the valves is thought to be of genetic origin, which means that little can be done to prevent it. However, accurate diagnosis and regular monitoring of valve function will prevent complications and ensure a good quality of life for patients.

When to call the doctor

If chest pain, tiredness or dizziness is experienced, medical attention shoud always be sought.

If any of the conditions that increase your risk for Barlow’s syndrome, or any applicable symptoms are experienced, a doctor should be seen as soon as possible.

Reviewed by Dr A.G. Hall (B.Soc.Sc.(SW), MB,Ch.B), December 2008