The mitral valve
Author Ольга Кияница
The mitral valve (mitral valve) is also known as the bicuspid valve or the left atrioventricular valve. It is a heart valve with two valves, which is located between the left atrium and the left ventricle. The mitral valve, together with the tricuspid valve, is known as atrioventricular valves, because they lie between the atria and ventricles of the heart.
Under normal conditions, blood flows through the open mitral valve during diastole with contraction of the left atrium. The MC is closed during systole with contraction of the left ventricle.
From the work of the MC depends the flow of blood through a large range of blood circulation, through which oxygen and nutrients flow to most of the organs and systems of the body. If there are any violations, the blood can flow back through the valve flaps (mitral regurgitation) or the MC is so narrow (mitral stenosis) that blood is difficult to get from the atrium to the ventricle. Rheumatic heart disease often affects the mitral valve; which can also prolapse with age or be affected by infective endocarditis.
Video: The mitral valve of the heart
The main characteristics of the mitral valve
The human heart has 4 valves. The mitral valve is 4 to 6 square centimeters and connects the left atrium (LP) and the left ventricle (LV). Opens MC during diastole, so that the flow of blood from the LP comes in the LV. During ventricular systole, the mitral valve closes and prevents backflow of blood
The word "mitral" comes from Latin, which means "in the form of a miter" (Bishop's hat). The word "bicuspid" is a combination of words from Latin "bi-", which means "double", and "cusp", which means "dot", which indicates a double flap-shaped valve shape.
The normal function of the mitral valve depends on six components:
- The walls of the left atrium
- Left atrioventricular ring
- Valve Closures
- Chordate tendons
- Papillary muscles
- The walls of the left ventricle
The mitral valve has two valves, an anteromedial valve and a posterolateral valve. The aperture of the mitral valve is surrounded by a fibrous ring, known as the mitral ring. On the front flap there are approximately two thirds of the valve (it is a crescent in the circle) and it is located above the rear flap.
Any congenital or acquired disruption of individual components of the mitral valve can disrupt its finely coordinated mechanisms and reduce the functionality of the MC.
Anatomy of the mitral valve
The mitral apparatus consists of the left atrium wall, the ring, the valves, the chord tendons, the papillary muscles and the wall of the left ventricle. The valve is located obliquely behind the aortic valve.
Left atrial wall
The left atrial myocardium extends to the proximal part of the posterior wing. Thus, an increase in the left atrium may lead to mitral regurgitation, since the mitral ring is stretched. In this case, the front flap is not broken due to its attachment to the base of the aorta.
The mitral ring
It is a fibrous formation that connects with the valves. This hole is not an integral, but a D-shaped, similar shape is made by prosthetic valves.
The normal diameter of the mitral ring is between 2.7 and 3.5 cm, and the circumference is between 8 and 9 cm
The border of the mitral ring is located behind the aortic valve, which is located between the ventricular septum and the mitral valve. The ring functions as a sphincter, which compresses and reduces the surface area of the valve during systole, which allows for complete closure of the valves. Thus, dilatation (expansion) of the mitral ring causes a poor closure of the valves, which leads to mitral regurgitation.
Free edges of the leaves have several depressions. Two of them, anterolateral and posterior medial, divide the valves into the anterior and posterior ones. These commissures can be accurately identified by insertions of the commissural chord tendons into the sashes
Normally the valves are thin, flexible, translucent and soft. Each valve has an atrial and ventricular surface.
- Front sash
It is located behind the root of the aorta and is attached to it, unlike the posterior wing. Accordingly, this leaf is also known as aortic, septate, large or anteromedial. The front leaf is large and semicircular in shape. It has a free edge with small depressions or without them. The two zones on the anterior valve are called coarse and transparent, in accordance with the passing chordinal tendons. These two zones are separated by a crest on the atrial surface of the valve, which is the line of its closure. The crest is located approximately 1 cm from the free edge of the front flap.
Distal to the ridge is a rough zone, shaped like a crescent.
- Rear leaf
Also known as ventricular, smaller or anal valve. It is a patch of mitral valve that is located behind two commissural areas. It has a wider attachment area to the annular space than the front leaf. It is divided into 3 scallops and 2 grooves or crevices. The average scallop is larger than the other two (anterolateral and posterolateral commissural).
Cup-shaped tendons are small fibrous strings that begin either from the papillary muscles, or directly from the ventricular wall, and attach to the valve flaps or muscle. There are 2 types of chords, called true and false.
The normal average length of the chords is about 20 mm.
The normal average thickness of the chords is 1-2 mm.
- Commissural chords
They are called so, because they are attached in the commissural areas located at the junction of the front and back sashes. There are two types of commissural chords. Postmedic commissural chords are inserted into the posterior medial area of the commissure; whereas the anterolateral commissural chords are inserted into the anterolateral commissural region. Most of the main branches of the commissary chords go to the center of the commissural sections.
- Valve chords
Attached to the front or rear flaps. Two types of chordal tendons are attached to the anterior valve. The first are the rough chords, which are inserted into the distal part of the anterior valve, called the rough zone. The second are the chords that are located before insertion into the front sash.
The posterior wing has 3 types of chordate fibers. The first are the rough chords, which are the same as the rough chords of the front leaf. The second - basal chords, specific for the posterior valve.
Papillary muscles and the wall of the left ventricle
These two structures are the muscular elements of the mitral valve. Papillary muscles usually stretch from the top and middle third of the wall of the left ventricle. The anterolateral papillary muscle is usually larger than the posteromedial papillary muscle, and is provided with the left anterior descending artery or the left peripheral artery. Pathological fusion of the papillary muscles can lead to mitral stenosis. On the other hand, the rupture of the papillary muscle, usually a complication of acute myocardial infarction, leads to acute mitral regurgitation.
Video: Mitral Valve - Anatomy, Function & Area - Human Anatomy | Kenhub
Two-dimensional and three-dimensional echocardiography of the mitral valve
Echocardiography is a clinical tool of choice for diagnosis, evaluation and monitoring of patients with valvular heart disease. It is a non-invasive, non-ionizing visual test with excellent spatial and temporal resolution. Two-dimensional (2D) and three-dimensional (3D) echocardiography (echocardiography) provides a detailed morphological and functional evaluation, while Doppler echocardiography evaluates hemodynamics. Functional mechanisms of mitral regurgitation in many conditions were first clearly defined echocardiography. The continuous development of information technology makes research a very portable and increasingly important tool for conducting a minimally invasive percutaneous study of valves.
3D echocardiography is crucial for today's understanding of the normal and impaired mitral valve device: the 3D echocardiography has made it possible to establish a saddle-shaped, non-planar form of the mitral ring, to investigate the complex geometric relationship between the position of the chords in relation to the mitral ring and the outflow tract of the left ventricle [1 - An integrated mechanism for systolic anterior motion of the mitral valve in hypertrophic cardiomyopathy based on echocardiographic observations.
Jiang L, Levine RA, King ME, Weyman AE, Am Heart J. 1987 Mar; 113 (3): 633-44]. Also, with the help of echocardiography, it was recently possible to determine the size of the mitral valve during palpitation [2 - The unsaddled annulus: biomechanical culprit in mitral valve prolapse?
Jensen MO, Hagège AA, Otsuji Y, Levine RA, Leducq Transatlantic MITRAL Network.
Circulation. 2013 Feb 19; 127 (7): 766-8].
The correct diagnosis of the mitral valve disease depends on the optimal 2D echoes. A three-dimensional understanding of the anatomical structure of the heart is of paramount importance for the acquisition and interpretation of 2D images.
3D echocardiography allows to eliminate uncertainty in the conclusions, because the obtained 3D-data can be accurately cut in each measurement until the optimal and desired 2D-representation is obtained. As a result, the violations and changes in the valvular apparatus are determined with greater accuracy.
Mitral valve diseases
Disease MK is characterized by a change in blood flow from the left ventricle (LV) to the left atrium (LP). The development of mitral regurgitation varies and largely depends on the etiology, severity and onset of the disorder.
The transesophageal echocardiogram in the apical three-chamber view with the color doppler of the mitral valve makes it possible to identify a mismatch, which is consistent with an elevated gradient through the mitral valve secondary to stenosis. Also during the study, a backward directed stream of blood flow is seen with severe mitral regurgitation.
It is characterized by a narrowing of the opening of the left ventricle at the level of the mitral valve as a result of the structural anomaly of the valve apparatus. The most common cause is rheumatic heart disease.
Mitral valve prolapse
It is the most common valve anomaly, defined in 2-6% of the population of the United States. Often, it is the cause of the formation of isolated mitral regurgitation. The prolapse of the mitral valve in classical form proceeds according to the type of displacement of the mitral valves more than 2 mm toward the left atrium during systole with a leaf thickness of at least 5 mm. Similar indicators are detected using transthoracic echocardiography.
Video: Mitral valve prolapse. The disease of superflexible people
- The organization of the mitral valve is a complex three-dimensional functional system, which is crucial for unidirectional blood flow through the heart.
- The main components of the mitral valve are: 1) mitral ring, 2) mitral valve flaps, 3) chords and 4) papillary muscles.
- Chords play a key role in the structure and function of mitral valves.
- The productive work of the MC depends on the balance of closing forces of the valve flaps in the systole and on the size of the valve itself.
- Understanding the structure and function of all components can help in the diagnosis of pathology
- The front flap is better fixed than the rear wing, which contributes to the more frequent exposure of the rear flap to remodeling, distortion of shape or damage
- The anterior valve is not anatomically divided into scallops, unlike the posterior wing, although pathological formation on the anterior side imitates scallops similar to the posterior wing
- Scallops are marked from 1 to 3 on the basis of lateral and medial segments
- As to which papillary muscles the chords go from and from which scallops the following distinctions exist:
- Anterolateral papillary muscle = lateral scallops and lateral half
- Median papillary muscle = medial scallops and medial half
- The visualization of the scallops may vary depending on the scanning method and the angle of inclination of the scanning element
- Echocardiography is ideal for examining the mitral valve apparatus and gives an idea of the mechanism of MC disease.
Understanding the normal function of the mitral valve is important to monitor changes in the progression of the mitral valve disease and to provide rationale for developing recovery strategies.
An important anatomical component of the heart is the valve apparatus. Without it, the blood could not move unidirectionally, which is why it is extremely important that all the valves are in a normal state and function properly. Variants of the norm and the physiological features of the valvular heart apparatus will be considered.
Among all heart defects, prolapse of the mitral valve is quite common. The disease is of three degrees of severity, and the most favorable prognosis is given by the prolapse of the mitral valve of the 1st degree. For proper treatment and prevention of disease, its symptoms should be properly identified.
The development of heart failure is mainly accompanied by the appearance of a symptom such as shortness of breath. Depending on its severity, the patient's condition may be disturbed to a greater or lesser extent. The occurrence of shortness of breath often indicates the progression of the underlying disease and the need for emergency medical treatment.