All About the Mitral Valve: Anatomy, Physiology and Disease

What is the mitral valve and where is it located?

The main functional feature of the cardiac valve apparatus is to overcome resistance in the peripheral and main large vessels, which normally maintain a certain pressure. In the left half there are bicuspid and aortic valves, in the right - tricuspid and pulmonary valve. These structures perform the main task of maintaining stable hemodynamics, directing blood flow and preventing backfilling.

Depending on the phase of contractility of the cavities, the left atrioventricular opening acts as a damper to prevent regurgitation (reverse flow of blood into the atrium) or a funnel, which facilitates flow from the bicuspid valve to the aorta.

Topography

The heart is a four-chambered organ, divided by septa into two ventricles and atria, which communicate through the atrioventricular openings. The mitral valve is located between the left heart. It is projected at the spacing level of the fourth and fifth ribs. With auscultatory listening with a phonendoscope, physiological tones are determined in the fifth intercostal space, in the region of the cardiac apex, which is in contact with the chest wall.

Structure

The mitral valve of the heart (MC) consists of a fibrous opening and cusps, which are attached around its circumference. The structure of the MC includes tendon chords, papillary papillary muscle fibers adjacent to the cardiac myocardium of the left ventricle, and its own fibromuscular ring. Each element ensures the normal functioning of the MC.

Anatomy of the left atrioventricular foramen:

• The MC is divided into two valves by commissural septa, of which the anterior one is more round and longer, the posterior one is short and somewhat resembles a square;
• in some cases there can be from 3 to 5 valves;
• the number of additional elements depends on the size of the annulus fibrosus (FC);
• in the places where the valves are closed, papillary muscle fibers are attached (normally in humans, up to 3 anterior and 1-5 posterior muscles);
• tendon fibers (chords) are attached to the fibrous surface of the MC, directed into the cavity of the left ventricle, which are then divided into threads to each valve;
• the movement of structures, depending on the phase of contractility, is smooth and precise;
• All elements provide full opening of the bicuspid mitral valve of the heart in the diastole phase of the antiphase - the multidirectional physiological movement of the valves, facilitating the outflow of blood.

The histological structure of the mitral valve

The main tissue components of MK:

• valves formed by a three-layer connective tissue, attaching to the atrioventricular opening;
• own valve ring of fibrous and muscle tissue;
• the inner surface is lined with a shell of the heart, endocardium;
• the middle section is made of spongy tissue.

What the mitral valve of the left heart looks like and what it is is shown in the photo below:

Mechanism and features of work

The main function of the bicuspid atrioventricular valve is to prevent backflow (regurgitation) into the left atrium and direct its flow into the ventricle.

MK functions

All valve leaflets are mobile and pliable structures that move during contraction phases under the influence of directed blood flow. At the time of diastole, the muscles of the cardiac cavities relax and fill with blood, the large anterior valve of the MV closes the aortic cone, thereby preventing it from being thrown into the aorta.

During systole, with contraction of the atrium and ventricles, the elements of the left atrioventricular opening are compressed along the thickened valve lines, which are held by the chords. This prevents regurgitation and maintains normal hemodynamics in the systemic circulation.

Normal Valve Performance

Echocardiographic examination (ultrasound of the heart) highlights the average normal values:

• diameter of the fibromuscular ring 2.0-2.6 cm, valve up to 3 cm;
• MK area up to 6.5 cm²;
• the leaf thickness is 1–2 mm;
• movement of all valves is active and smooth;
• the surface is homogeneous and even;
• in the systole phase, the deflection of the elements into the cavity of the ventricle is not more than 1.5-2 mm;
• chords in the form of long, linear and thin fibers.

The main pathologies and methods of their diagnosis

The main causes of acquired MC defects: rheumatic and atherosclerotic lesions, age-related and degenerative changes, the consequences of infectious inflammatory endocarditis against the background of sepsis. These diseases lead to narrowing and dysfunction of the atrioventricular opening, the development of insufficiency or stenosis. Complex combined defects often appear as a consequence of a severe course of rheumatic disease.

Frequent mitral valve diseases

MK prolapse - (protrusion or sagging) of the leaflets into the atrial cavity during systolic contraction. The defect is more common in newborns, the peak of detection occurs at the age of 5-15 years.

It can be primary (of undetermined origin) or secondary - the result of an inflammatory process or trauma to the sternum, more often in athletes. Dysplasia of connective tissue indicates a hereditary genetic disease.

The violation is characterized by:

1. Regurgitation of the bicuspid mitral valve disrupts blood flow, which is manifested by the development of pulmonary hypertension (increased pressure in the vessels of the lungs) and decreased parameters in the peripheral arteries.
2. Clinical symptoms depend on the degree of prolapse and the cause of the defect.
3. In the initial stages, the condition may deteriorate minimally, more often when playing sports.
4. Increasing weakness and dizziness, headaches, and loss of consciousness testify to the progression of regurgitation. Often, shortness of breath, shortness of breath at the slightest exertion, a feeling of lack of air are worried.
5. The risk of developing arrhythmias and cardiac arrest is high.

Insufficiency of the mitral valve - characterized by incomplete closure of the valves or their prolapse (sagging into the cavity), due to which the left atrioventricular opening during systole is not completely closed, and blood is thrown into the atrium.

Characteristics of pathology:

1. This is a congenital or acquired valvular disease.
2. The defect of closure causes damage to the valves, own connective tissue chords or papillary muscles, stretching of the annulus fibrosus.
3. Isolated abnormal MC is rare, more often a combined defect.
4. Common causes: separation or rupture due to trauma or heart attack, the outcome of an inflammatory disease of a rheumatic or autoimmune nature.
5. Prolapse can lead to failure.
6. Fatal insufficiency develops with regurgitation of more than 55-90% of blood in the contraction phase.
7. With a defect, right ventricular failure occurs with an increase in volume and expansion of the heart cavity.
8. The clinic appears when blood flow is limited by more than 40%.
9. Patients are worried about coughing with shortness of breath and hemoptysis, palpitations, periodic cardiac pains.
10. A frequent dangerous complication is atrial fibrillation.

Mitral valve stenosis: with a similar pathology, the area and diameter of the left atrioventricular opening decreases and narrows, which limits blood flow through the MV and further into the aorta. This is an acquired defect, in 45% of cases it is combined with such valve defects: mitral insufficiency, damage to the aortic or right (tricuspid) valve.

Main characteristics of stenosis:

1. The rheumatic nature of education. After the first signs of an inflammatory disease at the age of 18-25, stenosis develops within 10-25 years.
2. The valve defect can be caused by infective endocarditis and sepsis, a consequence of opium addiction, a complication of a severe course of syphilis or atherosclerosis.
3. In rare cases, it develops after valve surgery, with a heart tumor, progressive calcification of the MK elements.
4. Clinical symptoms occur with a decrease in the area and diameter of the hole by 50% according to the classification, which significantly disrupts hemodynamics.
5. Compensatory for the alignment of blood circulation, the volume and muscle walls of the left atrium increase, hypertrophy develops.
6. The pressure in the upper left parts of the heart rises, which is manifested by pulmonary hypertension.
7. It leads to a decrease in the contractility of the left lower parts of the heart, ventricular dilatation develops with impaired blood flow in a large circle.
8. There is a high risk of developing arrhythmias, heart failure with pulmonary edema.
9. Clinically it is manifested by severe weakness, shortness of breath with cough, the appearance of sputum streaked with blood indicates a worsening of the condition.
10. Characterized by redness of the cheeks and nose, cyanosis of the fingers and nails. Edema of the subcutaneous fat of the abdomen, legs and feet.

What diagnostic methods can be used to determine the disease

To identify pathological changes in the mitral valve, carry out:

1. Electrocardiography - allows you to determine the hypertrophy of the left heart, atrium or ventricle.
2. Echocardiography - abnormal murmurs favor stenosis or prolapse with failure.
3. A chest x-ray to look for an enlarged heart.
4. Ultrasound of the heart with dopplerography of the great vessels - evaluates blood flow, its direction, hemodynamic stability; allows you to evaluate the work of the valves, the degree of closure and opening of the MC, prolapse, prolapse or regurgitation.

Examination and questioning of the patient

A general practitioner or cardiologist asks about the patient's complaints, when the condition first worsened, symptoms characteristic of each disorder appeared.

The inspection includes:

• auscultation (listening) of the heart valves with a phonendoscope, which suggests the presence of a defect or defect;
• definition of the boundaries of the heart;
• pulse counting, heart rate, blood pressure measurement;
• examination of the skin, assessment of the presence of edema, enlargement of the veins in the neck.

Instrumental diagnostic methods

1. Heart probing. After the introduction of the catheter through the vessel on the thigh or shoulder and its advance to the desired sections, the intracardiac pressure is assessed, the condition of the valves and septa is examined. This is an effective invasive technique in the operating room of a cardiac hospital.
2. Ventriculography. Unlike probing, an X-ray contrast agent is injected after catheter access. Thus, it is possible to identify valve defects, changes in the atria or ventricles.

Conclusions

Stenosis, prolapse or mitral valve insufficiency significantly impair the patient's quality of life. The severity of symptoms depends on the degree of hemodynamic disturbance. A chronic progressive course increases the risk of disability with a poor prognosis, mortality with the development of complications. When the defect is identified, all patients are prescribed treatment. Medications and drug regimens are less effective than minimally invasive surgery. The therapy is carried out in a cardiological hospital.