What is Mitral Valve Prolapse (MVP)?
Alternative names: Barlow's Syndrome; Floppy Mitral Valve Syndrome.
MVP is a relatively common syndrome 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 on the bottom. The leaflets of the valve are the thin strips of tissue which move when the valve opens or closes, depending on the state of heart contraction and relaxation.
In MVP, these leaflets do not open and close properly, but are floppy, and bulge into the upper left chamber, the atrium, as the heart contracts.
What causes Mitral Valve Prolapse (MVP)
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 other 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 gets MVP and who is at risk?
Mitral Valve Prolapse (MVP) occurs in between 1 - 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 of Mitral Valve Prolapse
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 and 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 click and 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 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.
MVP can result in severe dysfunction of the mitral valve, leading to what is called mitral regurgitation (MR)(a leaking, or incompetent valve). MR means that blood flows back into the left atrium during contraction rather then moving forwards into the aorta as it should.
About 25% of people with Mitral Valve Prolapse also suffer from lax joints, and a high arched palate in the mouth (these patients may have a degree of Marfan's syndrome) and other abnormalities of their skeleton such as scoliosis, a funnel chest and a straight back.
How is Mitral Valve Prolapse diagnosed?
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.
How is Mitral Valve Prolapse treated?
The most important factor is to assess the degree of prolapse and the degree, if any, of mitral valve regurgitation (leakage).
In the absence of significant valve dysfunction, symptoms such as dizziness, palpitations and migraine can be treated with approprite 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.
Patients who have definite clicks and murmurs when the doctor listens to their heart may need to avoid highly competitive sports.
If mitral regurgitation is present, then antibiotics should be taken during dental extractions or other procedures that may lead to the spread of bacteria through the blood. Bacteria may cause an infection of the valve, called endocarditis.
What is the outcome of Mitral Valve Prolapse?
No, or mild, prolapse can be managed medically - see above.
The severity of MR is a predictor of complications: moderate to severe MR can lead to sudden death, atrial fibrillation, rupture of the chordae, heart failure, 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.
When MVP results in severe mitral regurgitation, heart valve surgery is required in order to prevent heart failure. Sudden death is rare.
The degeneration of the valves is thought to be geneticaly controlled, so there is little which can be done to prevent the condition arising. However, accurate diagnosis and regular monitoring of valve function will prevent complications and ensure a good quality of life in patients.
When to call the doctor
If you experience symptoms such as chest pain, tiredness and dizziness, you should always seek medical attention.
If you have any of the conditions which increase your risk for Barlow’s syndrome, and experience any appropriate symptoms, then see your doctor as soon as possible.
(Reviewed by Dr A. G. Hall)