Introduction
There are a total of four heart valves, each of which can be damaged by different causes in two directions. The four heart valves ensure that the heart is sufficiently filled during the relaxation phase and that the blood can be pumped in the right direction during the ejection phase. Ultimately, they are practically there to ensure that the blood is only pumped in one direction.
In heart valve disease, a distinction is made between stenosis and insufficiency. In a stenosis, the heart valves do not open completely, so that less blood can be expelled. This results in a narrowing at the level of the heart valve.
As a result, the blood accumulates in front of the narrowed valve and increased pressure must be applied to pump the blood further. An insufficiency, on the other hand, is practically a leak – the valve does not close tightly, so that blood can seep through the actually closed valve. Both stenosis and insufficiency put more strain on the heart.
The increased exertion causes the heart muscles to thicken and, as a compensatory measure, the chambers of the heart to enlarge. A larger heart must be supplied with more oxygen and nutrients than a healthy heart. In the long run, the supply of the heart muscles is not sufficient and a cardiac insufficiency develops. In the case of a cardiac insufficiency, the heart is no longer able to cope with the demands and it can no longer supply the body with sufficient oxygen-rich blood. A stenosis and insufficiency of a heart valve can be acquired in the course of one’s life, for example in the course of an inflammation (endocarditis = inflammation of the inner skin of the heart, which also covers the heart valves) or calcification of the heart valves, or it is a congenital disorder.
Function and anatomy of the four heart valves
In total there are four different heart valves: Aortic valve, pulmonary valve, tricuspid valve and mitral valve. The mitral valve in the left part of the heart and the tricuspid valve in the right part of the heart separate the atria from the ventricles. During the filling phase of the heart, the diastole, both valves are open so that blood from the body’s circulation can flow through the atria into the ventricles.
During the ejection phase, the systole, both valves are closed so that blood cannot flow back towards the atria. The other two valves, aortic and pulmonary, are located at the two exits of the heart. The pulmonary valve is located in the right chamber.
It represents the gateway from the right chamber to the pulmonary circulation. The pulmonary valve is the gateway from the right chamber to the pulmonary circulation, through which the oxygen-poor blood flows, which is then enriched with oxygen in the pulmonary circulation. The aortic valve is located in the left chamber of the heart.
Through the aortic valve, the oxygen-rich blood is pumped from the left ventricle into the body’s circulation. The aortic and pulmonary valves are closed during the relaxation phase so that the heart can first fill and build up sufficient pressure. During the ejection phase, these valves are then open.
Oxygen-poor, venous blood thus flows from the body’s circulation into the right atrium, from there via the tricuspid valve into the right chamber. Via the pulmonary valve, the blood then reaches the pulmonary circulation, which ultimately leads to the left atrium. The blood, now enriched with oxygen, flows through the mitral valve into the left chamber and from there through the aortic valve into the aorta, i.e. the arterial circulation of the body.
The blood can then supply organs and muscles etc. with oxygen and nutrients. There are two types of heart valves: the pocket valves and the sail valves.
The aortic valve and the pulmonary valve belong to the pocket valves. The tricuspid valve and the mitral valve, on the other hand, belong to the sail valves. The pocket valves are made of three crescent-shaped pockets and the material corresponds to the inner skin of the heart.
Aortic and pulmonary valves are similar in construction, but the aortic valve is larger and thicker because it is exposed to greater pressure in the left part of the heart than the pulmonary valve. The tricuspid valve consists of three sails, while the mitral valve (also called bicuspid valve) consists of two sails. The names of the two valves are derived from this.
The individual sails of the valves are attached to the so-called papillary muscles via fine tendon threads, which in turn project into the heart chamber. The way the sail valves are attached prevents the individual sails from penetrating into the atrium while the chamber is filling with blood. In the following, the stenosis and insufficiency of the individual heart valves will be discussed in more detail.Aortic valve stenosis is the most common heart valve disease.
Sometimes, aortic valve stenosis is combined with mitral valve insufficiency. In most cases, it is an acquired cause, such as inflammation or calcification. Calcification often occurs at an advanced age.
It is a degenerative process, with the result that the stenosis increases and the heart becomes more and more strained. Calcification is the most common reason for acquired aortic valve stenosis. Approximately three to five percent of all patients over the age of 75 years have aortic valve stenosis due to calcification.
High blood pressure, smoking, elevated blood lipid levels and diabetes promote both calcification of the vessels and corresponding calcification of the heart valves. This leads to reduced mobility of the valve so that it can no longer open completely. Congenital aortic valve stenosis, on the other hand, can be caused, for example, by the fact that instead of the usual three valve pockets, only two pockets have been created.
If calcification is then added, a stenosis may develop. If a stenosis of the aortic valve is present, this manifests itself from a certain degree of the disease onwards with various symptoms similar to those of an impending heart attack. On the one hand, there may be a feeling of tightness in the chest or chest pain (angina pectoris), as well as dizziness or even fainting.
(Caused by a temporarily too low blood pressure, so that the brain can temporarily not be supplied with sufficient blood). Also typical are shortness of breath or slight shortness of breath. All these symptoms usually occur with increased stress.
If the degree of stenosis increases, the symptoms also occur during light physical exertion. However, these symptoms are not specific for aortic valve stenosis, but can also occur in other valve diseases. Frequently, aortic valve stenosis or valve disease in general remains undetected because it occurs silently, i.e. without symptoms.
But how do these symptoms explain themselves? Due to the stenosis, oxygen-rich blood must be pumped with increased pressure from the left chamber into the aorta. After a certain degree of damage, blood remains in the left chamber.
As a result, more blood accumulates in the left chamber in the next phase, resulting in a higher load. The heart musculature thickens compensatorily and the ventricle ultimately becomes larger in the long run. At some point, the heart can no longer be supplied with sufficient oxygen, resulting in the development of heart failure.
If it is a severe aortic stenosis, which also manifests itself with symptoms, the valve must be replaced. Instead of a valve replacement, the aortic valve can also be “blown up” by means of a small balloon which is pushed forward towards the heart via a groin vessel and then inflated at the position of the heart valve, so that it can be fully opened again. In aortic valve insufficiency, the valve does not close properly during the relaxation phase, so that blood that was previously pumped into the body’s circulation can flow back into the left chamber.
If the heart now has to pump the blood back into the body’s circulation in the next cycle, a higher volume has built up. This means that the heart has to apply more force and pressure. As a result of the increased pressure, the chambers become larger and the muscle layer thickened, as in aortic stenosis.
Insufficiency of the aortic valve is usually caused by an inflammation (endocarditis). The inflammation can be caused, for example, by a bacterial infection, calcification, rheumatic fever (which is rare nowadays) or the autoimmune disease lupus erythematosus. The risk of a bacterial infection is increased if the valves are already damaged.
Congenital aortic insufficiency occurs only very rarely. In most cases, patients with aortic valve insufficiency do not experience any symptoms, since it is usually a gradual process to which the heart can adapt. In some cases, patients may notice an increased heartbeat (palpitation).
However, if the aortic valve insufficiency is acute, for example if a pocket is torn off during an inflammatory process, severe symptoms can result. If the insufficiency occurs acutely, the heart is not able to grow and blood backs up into the pulmonary and body circulation. This can lead to pulmonary edema, as well as edema of the lower legs (fluid retention in the tissue).
Symptomatically, this manifests itself primarily in the form of shortness of breath.In contrast to a stenosis, there are other therapeutic methods available for an insufficiency in addition to a valve replacement. Before the valve is replaced, an attempt can be made to reconstruct the valve to a certain degree of damage so that it closes sufficiently again. If mitral valve stenosis is present, blood cannot flow sufficiently from the left atrium into the left chamber because the valve does not open completely.
In the left atrium, therefore, increased pressure and correspondingly increased muscle work must be applied to pump the entire blood volume into the left chamber. Acquired causes of stenosis of the mitral valve can also be inflammation or degenerative processes – the typical cause, however, at 99%, is rheumatic fever, unlike the other valve diseases. But congenital causes can also trigger stenosis of the mitral valve.
The stenosis causes blood to accumulate in front of the left ventricle in the left atrium. If the heart is not able to control the situation, blood can back up into the pulmonary circulation. The patient perceives this as shortness of breath.
In the long run, the pressure in the pulmonary circulation increases, which is normally very low, so that the right heart has difficulty pumping the blood further. This leads to right heart failure. The chronic increase in pressure in the left atrium can also lead to atrial fibrillation, which increases the risk of blood clots forming, resulting in a stroke or pulmonary embolism.
If the stenosis is so advanced that heart failure occurs, the main symptoms are shortness of breath and fatigue. Due to the backlog of blood in the body, fluid accumulation occurs on the lower legs, the veins in the neck are congested and congestion can occur within the liver. In addition, a nocturnal and sometimes bloody cough can occur.
If the valve becomes symptomatic, heart failure can be treated with medication. However, a surgical valve replacement is also possible. As in the case of aortic stenosis, a balloon dilatation is also possible.
In the past, mitral valve stenosis was relatively common in the context of rheumatic fever, which can be caused by a scarlet or streptococcal infection. Since the medicine is meanwhile more advanced and the infections can usually be treated by an early antibiotic administration, mitral valve stenosis has become very rare. Mitral valve insufficiency is, after aortic valve stenosis, the second most common valve disease.
It results in a reduced ability to close the mitral valve between the left ventricle and the left atrium. The leak allows blood to flow back into the left atrium during the ejection phase. This results in a volume strain of the left atrium.
At the same time, however, more blood is pumped into the left chamber during the next filling phase, so that the volume of the left chamber is also strained. Eventually, the blood can congestion back into the pulmonary circulation and heart failure develops. The symptoms are similar to those of other valve diseases: Decreased performance, fatigue, exertional breathlessness and heart stumbling.
Sometimes atrial fibrillation can also occur. Mitral valve insufficiency is divided into acute and chronic disease. The chronic disease remains clinically silent for a long time and the symptoms appear only insidiously.
In acute disease, the symptoms appear quickly. Reasons for acute mitral valve insufficiency are, for example, bacterial infection of the valves (endocarditis) with destruction of the pocket valves and/or the tendon sutures. In the course of a heart attack, the papillary muscles, which are also essential for the function of the sail valves, may be torn off.
The most common cause of chronic insufficiency is a protrusion of the mitral valve into the left atrium (mitral valve prolapse), which is normally prevented by suspension from the tendon threads and papillary muscles. Due to the protrusion, the valve cannot close properly. Endocarditis, coronary heart disease, autoimmune diseases or the use of appetite suppressants can also provoke a chronic disease.
Before replacing the valve in symptomatic mitral valve insufficiency, the valve is first surgically reconstructed. While other valve diseases are often acquired, pulmonary valve stenosis is usually congenital. In pulmonary valve stenosis, the pulmonary valve does not open completely, so that blood accumulates in front of the valve in the right chamber.
This leads to pressure in the right chamber.The valve disorder is usually asymptomatic over a long period of time and only manifests itself with more severe damage in the form of chest pain (angina pectoris), shortness of breath and occasional fainting spells (syncope). The symptoms occur in the course of right heart failure. In most cases, an attempt is made to dilate the heart valve by means of a small inserted balloon so that it can open again completely.
Glued valves can thus be blown open. This operation is already performed on children, since pulmonary valve stenosis often occurs in childhood. Surgery is necessary if the opening area of the valve is severely restricted.
If the damage is only slight, those affected usually remain symptom-free until adulthood. If the valve is already too badly damaged, an artificial valve must be inserted instead of a balloon dilatation. In childhood, one tries to avoid a valve replacement, because the new valve does not grow like the body’s own valve and thus over time is no longer able to meet the body’s demands.
If the pulmonary valve is not completely closed during the filling phase, blood can flow from the pulmonary circulation back into the right chamber. As a result, during the next ejection phase, the right chamber has to apply increased force to pump more volume into the pulmonary circulation. In the long run, the right half of the heart becomes enlarged and right heart failure develops.
In most cases, pulmonary valve insufficiency is a permanently symptom-free disease. It can be caused, for example, by endocarditis, rheumatic fever, trauma during heart surgery or it can be congenital. In most cases, however, it is caused by increased pressure in the pulmonary circulation.
Pulmonary valve insufficiency is practically a way for the body to reduce the pressure in the pulmonary circulation because there is less blood in the pulmonary circulation due to the leak. Pulmonary valve insufficiency is only treated secondarily. The primary aim is to treat the cause of the increased pressure in the pulmonary circulation.
Once the pulmonary pressure returns to normal, pulmonary valve insufficiency usually also recedes. The pulmonary valve is rarely replaced. This is considered when symptoms of heart failure already occur.
Tricuspid valve stenosis is one of the now rare valve diseases. It is usually triggered by rheumatoid endocarditis, which is now well treatable. When the stenosis occurs, it usually occurs in combination with another valve defect – this also applies to tricuspid valve insufficiency.
Thus, tricuspid valve stenosis often occurs in combination with mitral valve or aortic valve stenosis. However, tricuspid valve stenosis can also be congenital or occur in the context of various diseases, such as Fabry’s disease, Whipple’s disease or a carcinoid (hormone-producing tumor). Due to the stenosis of the tricuspid valve, blood cannot flow completely from the right atrium to the right ventricle during the filling phase.
This results in a volume strain of the right atrium. As a consequence, blood is backed up in the venous system and finally leads to right heart failure. If tricuspid valve stenosis with mitral valve stenosis occurs, there is usually no increase in pulmonary pressure.
This is because tricuspid valve stenosis prevents too much blood from flowing into the pulmonary circulation so that the pressure does not increase significantly despite mitral valve stenosis. Tricuspid valve stenosis thus has a prognostically favorable effect on an existing mitral valve stenosis. As a rule, if the tricuspid valve becomes symptomatic, it can be reconstructed and valve replacement is not necessary.
As mentioned above, diseases of the tricuspid valve rarely occur in isolation. The trigger of tricuspid valve insufficiency is usually not congenital but secondary to a valve defect in the left heart. If there is damage to the aortic or mitral valve, the blood accumulates back into the right heart so that the right heart wall including the valve is exposed to increased pressure.
The heart valve ring to which the individual sails are attached is pushed apart. This causes the sails to stand further apart and can no longer close completely. A pulmonary embolism has a similar effect, which also causes an increase in pressure in the right heart.
As with the other valve defects, however, endocarditis or the tearing of a tendon thread or papillary muscle can also be responsible.Whereby an infection of the tricuspid valve usually only occurs in people with a weakened immune system. Symptomatically, tricuspid valve insufficiency can lead to congestion in the body’s circulation. Depending on how badly the valve is damaged, there is the possibility of valve reconstruction as well as valve replacement.
