Vital role of heart valves
Our heart is arguably the most important organ we have. Its role is to continuously pump blood around the body, providing all the other tissues and organs with the oxygen and nutrients they need to do their respective jobs. It pumps a staggering 14,000 litres of blood a day and, when it stops, our tissues quickly start to die.
To maintain this complex job, the heart is cleverly designed – there are four chambers, two on the right side and two on the left. The top or upper two are called atria and the bottom two are called ventricles. The right and left atria receive blood coming into the heart and this is then pumped into the two ventricles and pushed out to the lungs (from the right side of the heart), or to the rest of the body (from the left side).
Between the atrium and the ventricle on each side of the heart – and also between the two ventricles and the main arteries – are little trapdoors known as valves. It is the valves’ role to make sure that the different chambers and exit holes in the heart shut and open when they should, ensuring an efficient pump mechanism.
The four valves are known as:
■ The tricuspid valve which sits between the right atrium and the right ventricle.
■ The pulmonary valve which sits between the right ventricle and the pulmonary artery, the vessel that carries blood to the lungs to be oxygenated.
■ The mitral valve sits between the left atrium and the left ventricle.
■ The aortic valve sits between the left ventricle and the aorta, the huge artery that distributes oxygenated blood around the body.
To work effectively, our valves need to:
■ Be properly formed and flexible.
■ Open completely to allow blood to flow freely all the way through.
■ Shut tightly so that no blood flows back through them again into the chamber.
Any damage to a valve, resulting from a birth defect (known as congenital valve disease), an acquired disease or trauma, will impact on how effectively the valve works, and hence how efficiently the heart can pump. The main valve issues can be simplified into two groups:
■ Stenosis – a narrowing of the valve opening, which means that blood flow through it is restricted.
■ Regurgitation – also known as an ‘‘incompetent’’ or leaky valve, this occurs when the valve can’t shut tightly, allowing some backflow of blood.
Any of the valves can become affected by either stenosis or regurgitation, but the most common types involve the aortic and mitral valves. Although the symptoms associated with heart valve disease can vary depending on the valve involved, the following might indicate there could be an issue:
■ Shortness of breath – initially with exertion, but as the valve gets more damaged this can occur at rest, too.
■ Fatigue
■ Fainting and dizziness
■ Palpitations – often described as a racing or irregular thumping in the chest.
■ Chest pains or angina
■ Swelling of the ankles
■ Cough, often with pink-stained mucus.
■ Distended abdomen, which can occur if there is a lot of congestion in the liver.
■ Flushed red cheeks – this is specific to mitral valve stenosis.
Depending how severe the damage is and how long it has been going on, these symptoms can be extremely disabling.
There are several things that can lead to heart valve disease, but the most common are:
Ageing
As we get older, our valves lose their flexibility and can start to calcify. This can lead to stenosis or narrowing of the valve. The tissues supporting the valves can also lose their elasticity, making the valves prone to leaking or regurgitation. This is the most common cause of valve problems, particularly in older people.
Rheumatic heart disease
Anyone who has had rheumatic fever, especially if it isn’t treated promptly, is at risk of developing valve damage later in life. Sadly, New Zealand continues to have particularly high rates of rheumatic fever, especially among Ma¯ ori, Pasifika and those living in lower socio-economic areas.
Congenital valve disease
Congenital means ‘‘from birth’’ and sadly some babies are born with faulty valves.
Infective endocarditis
This is a rare infection, affecting the heart valves themselves, and often leads to lasting valve damage. It is more common in people who already have either damaged or artificial valves, or are immune suppressed in some way.
Cardiomyopathy This is a condition affecting the heart muscles and can be caused by a variety of things, including infection, pregnancy, alcohol and drug use, autoimmune diseases and severe dietary deficiencies.
If there is any concern that you may have a valve issue – either because you have some of the symptoms outlined, or because your doctor or nurse has picked up a ‘‘murmur’’ (an abnormal noise in your heart) during a routine examination – you will be asked to have more tests to try to ascertain what is going on.
These might include an ECG (a tracing of your heart rhythm), an echocardiogram (a scan that can look at the structure and function of the heart), blood tests and a chest X-ray to check your lungs look OK. Further testing will depend on your symptoms and will probably be carried out by a heart specialist known as a cardiologist.
If you are diagnosed with heart valve disease, don’t despair – it’s definitely better to find out sooner rather than later. The longer damaged heart valves are left without treatment, the harder the heart has to work to compensate for them – eventually, this will ‘‘wear out’’ the heart muscle, leading to heart failure.
Treatments offered will depend on what valve is affected and whether it is leaky or stenosed.
Medications such as ACE-inhibitors and diuretics can be used to reduce the ‘‘workload’’ on the heart and lower the likelihood of heart failure in the future and blood thinners can be used to reduce the risk of a clot.
Some people with damaged valves will require surgery of some sort, to either stretch, repair or replace the valve affected, but these operations are highly effective and often result in huge improvements in quality of life.