The condition is not named after anything medical or anatomical, but simply because the mitral valve in the heart resembles a Bishop’s Mitre in shape. Around 2% to 3% of the population suffers from mitral valve prolapse, but it is not usually considered a life-threatening condition. In some cases, however, it can be very serious, especially when there are complications in classic mitral valve prolapse.
The mitral valve is found between the atrium, the upper left chamber of the heart, and the ventricle, the lower left chamber. When it doesn’t close properly, but billows or bulges in a concave fashion back into the atrium, it is said to be in prolapse.
The mitral valve leaflets need to displace 2 millimetres or more above the high points of the mitral annulus before a prolapse of the valve is considered to have taken place. Below the 2 millimetre displacement threshold, no prolapse occurs.
Alternative names for mitral valve prolapse
The condition is also commonly known as Barlow’s syndrome, after John Brereton Barlow who was the first to describe it in 1966. Dr. John Michael Criley, Professor Emeritus at UCLA, is credited with subsequently coining the more popular and more commonly used term, mitral valve, to which prolapse is added to describe what is taking place.
It is also known under several other names. These include: floppy mitral valve syndrome, balloon mitral valve, myxomatous mitral valve, click-murmur syndrome, prolapsing mitral valve syndrome, billowing mitral valve, and as already mentioned, Barlow’s syndrome. To confuse matters even further, the mitral valve is also, and more properly, known as the bicuspid valve.
Subtypes of the condition
There are a number of subtypes of mitral vale prolapse. The primary subtypes are classic and non-classic. The subtypes of symmetric and asymmetric depend on the primary subtype of classic being present, and the further subtypes of flail and non-flail depend on the secondary subtype of asymmetric being present.
How does mitral valve prolapse develop?
The mitral valve has to leaflets, or flaps. One is anterior and the other is posterior. When the left ventricle contracts, they both close. The leaflets are made up of three different layers of tissue, known respectively as spongiosa, fibrosa and atrialis.
When classic mitral valve prolapse is present, there is an excess of connective tissue between the layers, which has the effect of thickening the spongiosa layer. It also separates bundles of collagen, the main component in the connective tissue, in the fibrosa layer.
This has the overall effect of weakening each leaflet, as well as the other tissue in the immediate area. The chordae tendineae, which is mostly made up of collagen, becomes elongated, which often results in rupture. This most commonly happens to the posterior leaflet chordae. The leaflet, again most commonly the posterior one, can become folded and displaced towards the left atrium. This is the condition we call mitral valve prolapse.
Who are most at risk from developing the condition?
People with a low body mass index, a ratio between a person’s body weight and height, tend to be found more often among patients with mitral valve prolapse. These are typically people who are lean and not overweight. The reason why people with a low body mass index should be more prone to developing this condition is unknown. It is merely an observation made over many years.
There are a number of diseases where mitral valve prolapse is found to occur in a significantly greater frequency. These diseases include Graves disease, polycystic kidney disease, Marfan syndrome and Ehlers-Danlos syndrome. The condition is also found in greater frequency in patients who have pectus excavatum, a deformity of the chest wall.
Rheumatic fever is known to sometimes be responsible for damaging valves in the heart. Rheumatic fever has become much less common in western developed countries, but remains a problem in many under-developed third-world countries. The prevalence of mitral valve prolapse in these countries, as a direct result of a higher incidence of rheumatic fever, also remains elevated.
Diagnosing mitral valve prolapse
Diagnosing the condition is usually done through indirect observation using echocardiography. This is a non-invasive technique that uses ultrasound to create an image of the heart and its workings. It is used in a similar way to the process that produces the more familiar ultrasound images of unborn babies in pregnant women.
Three dimensional echocardiography allows physicians to “see” the heart and to observe the mitral leaflets and their relative positions to the mitral annulus very accurately. The leaflet thickness can then be measured, as can the their relative displacement with regard to the annulus.
If the leaflets are observed to be thicker than 5 millimetres, and displaced by more than 2 millimetres, a diagnoses of classic mitral valve prolapse will result. More careful observation using echocardiography can then determine whether the subtypes of symmetric, asymmetric, flail or non-flail are also present.
Should I worry that I might have mitral valve prolapse?
Unless you have worrying symptoms, such as shortness of breath, palpitations or chest pain, then there usually is nothing to worry about. The majority of people who have mitral valve prolapse have no symptoms, and are usually given no treatment either as they are deemed to not need any treatment. Their lives are normal and the condition does not impact them in any adverse way. They may not even know that they have the condition.
However, a minority of people with the condition may require medication to ease the symptoms, and an even smaller minority of people will require surgery to correct their heart valve problems.
It is possible for the condition to cause problems, such as an irregular heartbeat, or arrhythmias. It can also result in infective endocarditis. This is a condition whereby the inner linings of the chambers of the heart develop an infection.
For the majority of people with mitral valve prolapse, life on a day to day basis is perfectly normal. However, it is advisable for anyone with the condition who has no symptoms to give up tobacco, alcohol and caffeine.