- Heart valve disease refers to any condition affecting the function of any or all of the four valves of the heart. The valves are located in specific positions, and each valve has a specific function.
- Infection, ischeamic heart disease and congenital abnormalities are important causes of valve disorders.
- Two serious possible complications are bacterial endocarditis and heart failure.
- The initial treatment is often medical, but the definitive treatment is surgical.
What is heart-valve disease?
Heart-valve disease (HVD) refers to any condition disrupting the normal function of the heart valves.
Where are the heart valves located?
There are four valves in the heart: two are inlet valves, two are outlet valves.
Valves are special tissue leaflets located between the heart chambers, permitting blood flow in one direction only. Their position allows them to function as inlet and outlet valves for the important pumping chambers (the left and right ventricles) of the heart. Inlet and outlet valves have a slightly different structure, but their function is the same, i.e. to permit flow in one direction only.
All valves consist of a ring-shaped structure, with the leaflets attached to the inside surface. These open and close. The outlet valves have three halfmoon-shaped leaflets.
Inlet valves have leaflets shaped more like the sails of a boat, and these are attached to specialised heart muscles inside the ventricle, called papillary muscles. These act as "guy ropes" to help stabilise the leaflets against the high pressures within the ventricles.
The heart is a double pump. One side (the right-hand side) receives used blood from the body, and pumps it on to the lungs where oxygen is replenished. This oxygen-rich blood then returns from the lungs to the left side of the heart, which in turn pumps it out to supply the whole body.
Once body tissues have extracted the oxygen from the blood, the oxygen–depleted blood is returned to the right side of the heart again, and the cycle is repeated.
How do they work?
This tricuspid valve (TV) is found between the right atrium (RA) and right ventricle (RV), and regulates the inflow of "used" blood from the body returning to the heart.
Blood enters the RA and passes through the open TV to the RV. When the RV is full, it contracts to pump the blood onwards to the lungs, where oxygen is replenished. With this contraction, the inlet TV closes so that none of the blood in the RV can squirt back into the RA.
In this way, all the blood is pumped forwards through the pulmonary valve into the lungs.
Pulmonary valve (PV)
The pulmonary valve (PV) is the outlet valve of the RV. This valve is open when the RV contracts (when the TV is closed) so that the blood can only be pumped forwards to the lungs.
The RV thus has an inlet and an outlet valve, controlling the blood flow through the RV. When the RV is relaxed and filling, the inlet valve (TV) is open, and the outlet valve (PV) is closed. When the RV contracts to eject its blood to the lungs, the TV closes and the PV opens.
This occurs with each contraction, ensuring that blood flows in one direction only - that is, onwards towards the lungs.
Mitral valve (MV)
This is the inlet valve for the left ventricle (LV), and is situated between the left atrium (LA), which receives the oxygen-enriched blood returning from the lungs, and the LV which is the main pumping chamber of the heart. A fully open MV allows the LV to fill quickly. As the LV contracts to eject its blood, the MV must close to prevent blood leaking back into the lungs.
Aortic valve (AV)
This is the most important outlet valve – from the LV to the aorta.
It opens when the LV pumps its blood out to the rest of the body. When the LV has emptied, and relaxes (with the MV open) to receive its next load of blood for pumping, the AV closes, preventing any of the oxygenated blood from flowing backwards into the heart again.
The LV thus also has an inlet (mitral) and an outlet (aortic) valve, permitting blood flow in one direction only – that is, from the lungs, forwards into the rest of the body.
What problems can arise?
Mechanically, there are three basic possibilities:
- The valve does not close properly, and thus leaks – also called incompetence, regurgitation or insufficiency.
- The valve does not open properly – called stenosis – impeding filling or emptying of the ventricle.
- A combination of the above two conditions.
An important problem is that of infective endocarditis (IE). This is caused by a bacterial infection of an abnormal valve. The patient becomes extremely ill, and may even need emergency surgery to remove the diseased valve if the infection cannot be controlled by large doses of intravenous antibiotics. The infected valve usually starts to leak quite suddenly.
The condition can be prevented by appropriate use of prophylactic antibiotics. (See the section on "Outcome".)
Causes, symptoms and signs
The commonest causes of valve problems are:
- Infection, e.g. rheumatic fever and endocarditis
- Congenital valve defects
- Degenerative disorders, e.g. Marfan's and Barlow's syndrome or age-related stiffening/calcification
- Ischaemic causes, e.g. after an acute myocardial infarct (AMI)
For clarity, the causes and symptoms are best considered by dealing with each valve separately. Although many of the symptoms may overlap, each valve problem has its own unique murmur that will help the doctor to make the correct diagnosis.
Stenosis (narrowing) of the AV is most often due to childhood rheumatic fever (RF). After many years, the leaflets become thickened and stiff, often with heavy calcium deposits. As the valve can only partly open, this obstructs the outflow of blood from the LV, making the heart work much harder as it tries to keep delivering the normal amount of oxygenated blood to the body.
However, even without previous rheumatic fever, the valve leaflets may become stiff with advancing age, giving the same end result – a narrowed valve, resulting in an extra work-load for the heart.
Because the condition of measurable stenosis can take years to develop, symptoms may be minimal at first. As the obstruction increases, the patient may experience general tiredness, persistent cough, shortness of breath or even chest pain with exertion, palpitations and fainting spells.
Examination of a patient with these symptoms usually reveals a particular heart murmur, and there may be significant enlargement of the heart.
Regurgitation (leaking) of the aortic valve is most commonly due to childhood rheumatic fever, but can also result from anything causing dilatation (stretching) of the valve ring (the circular structure to which the leaflets of the valves are attached) such as Marfan’s syndrome, severe hypertension or aortic arch dissection.
Infection of the valve (i.e. infective endocarditis) is another possible cause. A stenotic valve (see above), which progresses to become totally rigid, may also fail to close properly, and this may give combined stenosis and regurgitation.
The blood which leaks back into the ventricle with each heartbeat is thus added to the normal amount coming in from the lungs: this means that there is extra blood for the heart to deal with all the time. This increased workload can cause chest pain on exercise, shortness of breath, fatigue, ankle swelling, rhythm disturbances and eventual heart failure.
Stenosis is nearly always due to rheumatic fever, although calcium deposits and stiffening of the valve leaflets can occur in older people.
Narrowing of this valve prevents the LV from filling completely and results in a buildup of blood in the LA, and eventually backwards into the lungs as well. This buildup can cause the LA to become stretched, eventually giving rise to symptoms of tiredness, difficulty breathing, persistent cough (occasionally blood-tinged sputum), frequent chest infections, and a high incidence of rhythm disturbances, notably atrial fibrillation.
This AF can, in turn, allow clots to form inside the heart, and these can cause a stroke.
Regurgitation (also called incompetence or insufficiency) is due to damage to the leaflets, to heart-wall muscle or to papillary muscles.
Leaflet damage is most commonly due to rheumatic fever or endocarditis, while muscle damage is most often seen after a heart attack. Most commonly, symptoms develop gradually over the years following rheumatic fever. However, damage to the valve apparatus caused by a heart attack or by rampant infection can cause symptoms (similar to those of stenosis) to appear very suddenly.
Marfan’s and Barlow’s syndrome, both of which have a degree of degeneration of connective tissue, can also result in regurgitation due to leaflet problems as well as stretching of the supporting valve ring.
Stenosis is usually congenital, and can occur alone or as part of other complex abnormalities, e.g. Fallot's tetralogy.
The narrowing prevents adequate blood flow from the right ventricle to the lungs, so the child remains short of oxygen and may (rarely) be cyanosed. (This refers to a blue-ish tinge to the skin due to inadequate oxygen in the blood.) As the whole body is deprived of oxygen, these children tend not to gain weight, and remain tired. Infants often have problems feeding as they are too short of breath to suck properly.
Incompetence is occasionally seen as a result of pulmonary hypertension due to heart failure. The amount of regurgitation, however, is usually not severe.
In some adults, pulmonary incompetence may occur as a complication after a surgical repair of a stenotic valve (e.g. Fallot's repair). In rare cases, endocarditis and carcinoid disease can give rise to pulmonary imcompetence.
Stenosis is uncommon, but when found, it is usually associated with previous rheumatic fever and concurrent mitral valve problems.
Stenosis prevents the right ventricle from filling, and the buildup of blood causes enlargement of the right atrium. Eventually the blood dams up even more, and the liver can become enlarged. Patients with this problem are usually fatigued, and may develop ankle and abdominal swelling.
Incompetence is found to a small degree, even in normal people. Conditions causing problems of the right ventricle, such as heart attack or cardiomyopathy, can lead to dilatation of the ventricle and subsequent valve leakage. Disorders of the left ventricle that give rise to pulmonary hypertension can also eventually result in tricuspid regurgitation as a back-pressure effect.
How is it diagnosed?
- The symptoms described by the patient will be very important, and the diagnosis will be supported by a murmur heard when the chest is examined. These heart murmurs vary in character, site and intensity, and provide much information on the state of the valve.
- A chest x-ray will show whether there is enlargement of the heart or congestion of the lungs.
- An ECG will give an overall indication of the state of the heart muscle, and will also diagnose any rhythm disturbances, which are a common complication of valve disease.
- The definitive investigation is the echocardiogram. This is a "real-time" ultra-sound, which shows the heart contracting and the valves opening and closing as it happens. An external echocardiogram can be done in the cardiologist’s rooms by a specially trained technician. A far better and more accurate kind, however, is a trans-oesophageal echocardiogram, or TEE. This is also a real-time ultrasound, but is done with the patient anaesthetised via a special probe that he/she swallows (very much like a gastroscopy). Very clear pictures and accurate measurements of blood flow and valve anatomy and function provide valuable information used in deciding on the best treatment for the patient.
- An angiogram may be recommended to examine the state of the coronary arteries if the ECG indicates there is concurrent arterial disease.
How is it treated?
All treatment can be categorised as either medical (i.e. non-surgical) or surgical.
Medical treatment is used to alleviate symptoms in patients whose valve problems are not yet serious enough to warrant surgery, or for patients on whom surgery is not possible for various reasons.
Several important aspects are:
- Reducing the workload of the heart, e.g. with digitalis to improve effective contractions.
- Reducing the amount of fluid the heart has to pump, e.g. with diuretics (water pills) to shed excess fluid and salt.
- Slowing the heart rate, e.g. with beta blockers.
- Keeping the blood pressure normal, using various medications.
- Anticoagulants. These are very important in patients with rhythm disturbances such as AF (see mitral stenosis). In AF, clots can form in the atrium causing a stroke, heart attack or fatal pulmonary embolism. Anticoagulants such as warfarin prevent these clots from forming.
For some types of narrowed valves, a procedure called balloon valvuloplasty can be tried. In this procedure, a balloon-tipped catheter is introduced into the heart, much like an angiogram. When the balloon is situated within the narrowed valve, the balloon is inflated to stretch the valve open. Once this is achieved, the balloon is deflated and removed. Only certain types of valve problems can be handled in this way, and the procedure is seldom a permanent cure.
Surgery for valves can only be done with the patient on the bypass (heart-lung) machine, as the heart must be stopped and actually opened for the surgeon to work inside the heart.
Some valves may be repaired. This is usually only done for leaking mitral and tricuspid valves, and rarely for aortic valves. The repair may involve:
- Inserting a supporting ring to reduce an overstretched valve ring to normal size, thereby eliminating the leak.
- "Tailoring" or trimming the cusps to allow better closure or less prolapse into the atrium.
- Specially placed sutures can help to “re-suspend” cusps.
In most cases, though, valve replacement is much more effective, and can be done faster than can a delicate repair. As many patients are elderly and often have other co-existing diseases, it may be a better choice to limit the time spent under anaesthetic and on bypass.
There are different types of valves that can be used. Mechanical valves are made of a virtually indestructible substance called pyrolytic carbon. Provided they are correctly inserted, these valves can last the patient’s lifetime. Because they are a foreign substance in the body and thus promote clot formation, the patient needs to use warfarin anticoagulant permanently. This may be a problem in young females who still want to have children, as warfarin in pregnancy can cause foetal defects.
Bioprosthetic valves are harvested from cow or pig tissue, and are treated to become inert (non-irritant). For this reason, they do not tend to cause clot formation and the patient may be spared using warfarin. The disadvantage is that these valves have a limited lifespan, and may calcify after 10-15 years, and thus need to be replaced. If the patient has permanent AF, then s/he will need to use warfarin anyway, but may still receive a bioprosthesis for other reasons.
What is the outcome?
Valve surgery usually has an excellent outcome, especially if done by an experienced surgeon. Technical problems can (rarely) be encountered during the insertion of the valve, and this may result in:
- A residual leak
- Rhythm disturbances, if the conduction tissue is damaged
- Persistent stenosis, if too small a valve is chosen
With time, the body tries to re-line the valve with the same cells lining the inside of the heart. If this becomes excessive, the overgrowth of tissue can act as an obstruction to the valve (sub-valvar pannus overgrowth) and the overgrown valve may then need to be replaced.
Most valve replacements allow the patient to resume a near-normal life, with moderate exercise etc. Attention to the need for anti-coagulantion is vital, as is antibiotic prophylaxis. Other co-existing problems must also be managed.
Once a patient has had a valve replacement, s/he must be made aware of the need for antibiotic prophylaxis. This consists of a special type and dosage to be used before any surgical procedure, no matter how minor.
Of crucial importance is that visits to the dentist must be covered: the bacteria most often implicated in infective endocarditis come from the mouth, and fillings, extractions and even cleaning by the hygienist have been shown to dislodge these bacteria from the gum margins. They enter the bloodstream and settle on the artificial valve, where they flourish, and can totally destroy the valve.
The same process occurs with any abnormal valve, and often happens to patients who have a known valve abnormality, but who are not yet candidates for valve surgery. An unprotected visit to the dentist or a minor operation can thus have catastrophic results when the patient’s own natural valve is suddenly destroyed.
Congenital valve abnormalities cannot be prevented, but they can be correctly managed to give the best quality life to the patient. Monitoring of valve function is imperative, as is the correct timing of interventive surgery.
Adequate public health interventions to reduce the incidence of rheumatic fever, and to provide rapid adequate treatment of diagnosed cases, will drastically reduce the incidence of valve disease, especially in populations where this is endemic. This will, in turn, reduce the incidence of valve problems.
Because some valve problems are associated with underlying disorders, it follows that proper management of these may prevent valve problems from arising, e.g. good control of hypertension can prevent heart enlargement/ heart failure which can cause valves to leak.
When to see your doctor
Symptoms such as persistent tiredness, coughing, rhythm disturbances and shortness of breath should immediately be investigated. Any chest discomfort – especially if it occurs with exercise – is also significant.
All patients with known or suspected valve problems should be in the care of a specialist cardiologist, who has the knowledge and expertise to manage them correctly. If you are such a person, please ask your cardiologist to explain further about antibiotic prophylaxis, and to give you a prescription for the medication currently recommended by the American Heart Association guidelines if you are planning a visit to the dentist or are about to have surgery.
If you know you have an abnormal valve, and you experience a sudden change in symptoms, or develop a fever, consult your doctor immediately. This may be infective endocarditis, and is considered a medical emergency.
Reviewed by Dr A.G. Hall (B.Soc.Sc.(SW), MB,Ch.B)