Mitral valve prolapse

Valve prolapse is not as common among individuals with WS but it does occur in some. In the world of congenital heart defects (CHD) which are heart defects present at birth, it actually affects about 2-3% of the CHD population.

What is a valve?

In order to understand how prolapse occurs, you should first be familiar with the function and anatomy of a valve. Valves are used throughout the cardiovascular system to direct blood flow. They act like one-way doorways that swing open, allowing blood to move through, and close behind, preventing it from flowing backwards. This essentially seals off each chamber in the heart so that when the muscles squeeze and push blood into a vessel, blood isn't pushed backwards. This is important for many reasons. Without valves, blood pressure would be more difficult to achieve. You wouldn't have the pressure of the blood pushing on the vessels if it had another outlet to flow into. Second, if there were multiple outlets, some blood could get caught in limbo between the two chambers, just swishing back and forth and not really moving anywhere. This is dangerous because it could cause it to clot. Clots can lead to several issues including heart attack. So, you can see, valves are important structures to keep everything flowing properly.

Valves are structured much like a balloon or parachute, attached to cords called chordae tendonae and anchored to the muscle wall of the ventricle (lower heart chamber). The valve itself is made up of cusps or flaps that fit together tightly to create a seal. On the left side of the heart you find the mitral valve between the two chambers (left atrium and left ventricle). The mitral valve also has two other names- the bicuspid valve, because it has 2 cusps or flaps, and the left a-v valve, because it separates the left atrium (a) from the ventricle (v). There is an analogous valve on the right side of the heart called the tricuspid or right a-v valve that functions in the same way and can also undergo prolapse for all the same reasons.

What does it mean to have valve prolapse?

When a person is born with valve prolapse, the layers of tissue that form the flaps or cusps of the valve are thicker than normal. The valve cusps are made up of three layers of tissue. One of those layers is connective tissue. When prolapse is present, the connective tissue builds up into a thicker layer than normal. This causes the cusp to fit improperly with the others and makes a leaky seal.

Most people with mitral valve prolapse show no signs of heart distress. If the seal does not allow too much blood to flow backwards, the overall function of the heart is maintained. Doctors will hear a murmur or click when they listen to the person's heart. A murmur is a swishing sound created when the blood squeezes through that opening. The smaller the opening, the louder the murmur will actually be.

Some people have a larger opening in the valve or it can progressively become worse over time. If the opening becomes large and a significant amount of blood flows backwards you can have issues with clotting and blood pressure. When blood flows backwards into the atrium it is called mitral regurgitation. If this occurs, a cardiologist will most likely prescribe medication called beta blockers or blood thinners to prevent clotting.

As the opening becomes larger, a lot of pulling can take place on the cords that anchor the valve. They can become stretched out, causing the opening to become larger still and eventually can rupture or break. You can imagine what would happen to a parachute if you cut one of the cords that attaches it. The parachute would become loose and wouldn't catch the air properly. The same thing can happen to the valve. If this happens, the heart simply wouldn't function properly and a valve repair or replacement surgery may be necessary.

If my child has valve prolapse, what can I do to prevent this from progressing?

Although the progressive nature of this condition can be scary, most people go their entire life without any issues. Whenever a child has a CHD, it's important to maintain optimal cardiovascular health by monitoring their diet, getting proper cardiovascular exercise and seeing a cardiologist regularly to monitor the defect. Diet, especially watching sodium intake and avoiding caffeine and energy drinks, will keep their heart functioning properly.

Sources:
Mitral valve diseases in Williams syndrome by Collins

Mitral valve prolapse by Medline