Mitral stenosis is an isthmic narrowing of the lumen of the atrioventricular aperture to the left, which exerts resistance to the blood flow to the left heart during the diastolic relaxation of the ventricles of the heart.
The incidence of mitral stenosis is significantly different in different countries and is more dependent on the prevalence of rheumatism in this area. The net mitral damage of the valvular heart apparatus accounts for an average of 60% of all heart defects, of which 75% of cases are women.
For the formation of stenosis of the mitral valve, the development of significant fibrotic changes in the valve, accompanied by confluence of the commissure, thickening and calcination of the valves, is characteristic. Along with these changes, mitral valve damage can be accompanied by some thickening, fusion and shortening of the tendon structures of the chords and the formation of a funnel-shaped mitral valve.
In a situation where mitral valve stenosis develops against rheumatism, morphological changes in the valve are caused by manifestations of rheumatic carditis in the acute period. Manifestations of stenosis of the mitral valve in this case rapidly progress, due to the permanent traumatic effect on the valve by increased blood pressure caused by severe cardihaemodynamics and progressive rheumatic inflammation.
Cardiohemodynamics with stenosis of the mitral valve is disrupted primarily, due to the formation of the first barrier in the form of a narrowing of the mitral orifice. In a situation where the total area of the mitral orifice is significantly reduced, conditions are created to prevent the blood from moving to the left heart, so there is a compensatory increase in the blood pressure gradient.
In the initial stages of stenosis of the mitral valve, compensatory pathogenetic mechanisms in the form of increased pressure in the left atrial cavity, as well as increase and increase of the systole level hemodynamic disturbances. Signs of increased blood pressure in the cavity of the left atrium in the compensated stage of stenosis of the mitral valve are noted only with excessive psycho-emotional and physical activity in order to ensure an increase in the minute volume of the heart. Increased pressure in the cavity of the left atrium is always accompanied by an increase in pressure in the venous system of the lungs.
A significant narrowing of the mitral orifice up to 1 cm 2 is accompanied by a marked increase in the pressure gradient in the cavity of the left atrium above the level of 25 mm Hg. Due to increased blood flow to the cavity of the left atrium, which occurs against the background of physical and / or emotional overstrain, the excessive liquid component of blood flows into pulmonary alveoli and the development of signs of pulmonary edema. In the initial stages of this process, the body works a protective compensatory mechanism in the form of a Kitaev reflex, consisting in narrowing the lumen of pulmonary arteries of small caliber, which initially has a transient character, and subsequently there is a persistent narrowing of the pulmonary arterioles.
In connection with the aforementioned compensatory effects, in the pulmonary vessels there is thickening and sclerosing of the vascular wall, resulting in complete obliteration of the lumen. Thus, pulmonary vascular resistance acts as an "additional barrier".
With exhaustion of compensatory mechanisms dilated cardiomyopathy of the right heart is developing, and stagnant signs are formed in the system of a large circulatory system.
Causes of mitral stenosis
The most common etiopathogenetic cause of development of signs of mitral stenosis is rheumatic lesion. Congenital malformation in the form of an isthmic constriction of the mitral orifice is extremely rare and develops only if all of the tendon chords are attached to a single papillary muscle.
Degenerative damage to the mitral valve, accompanied by a pronounced calcification of its ring, sooner or later provokes the development of acquired mitral stenosis. A rare, however, occurring cause of the defeat of the valvular apparatus in the form of mitral stenosis is the presence of multiple vegetations in the projection of the valve flaps observed in the infectious type of endocarditis , as well as the myxoma of the left atrium.
Some cases of severe prolonged flow of endocarditis, which occurs against the background of systemic involvement of connective tissue, result in the development of mitral stenosis.
Symptoms and signs of mitral stenosis
The initial signs of stenotic defeat of the mitral valve is progressive dyspnoea. In the initial stage of the disease, respiratory disorders are noted only with excessive physical activity, and when the defect progresses, not only shortness of breath with minimal physical activity, but also cough is observed.
A characteristic symptom of mitral stenosis is an increase in respiratory disorders in the horizontal position, so to ease the condition the patient occupies an orthostatic position. Respiratory disorders with mitral stenosis can reach a pronounced intensity up to the occurrence of choking, and the release of a large volume of pink foamy sputum indicates the development of alveolar pulmonary edema .
Mitral-aortic stenosis in almost 80% of cases is accompanied by the appearance of a recurrent hemoptysis caused by ruptures of numerous vascular anastomoses under the influence of increased pressure in the pulmonary veins. Also hemoptysis in some cases occurs as a result of complications of myocardial infarction and pulmonary edema in the interstitial phase.
With a decrease in the minute volume of the heart, there is a pronounced weakness and decreased ability to work. The occurrence of various forms of cardiac arrhythmias in mitral stenosis is considered rare, but episodes of arrhythmia significantly worsen the clinical manifestations of this defect. The most common form of rhythm disturbance is the persistent form of atrial fibrillation.
Signs of accession of right ventricular congestive heart failure are marked edema of peripheral localization, as well as a feeling of heaviness and discomfort in the upper right quadrant of the abdomen. Pain in the heart and stenocardic chest pain is an exception to the rule and does not refer to specific signs of mitral stenosis.
Despite the predominant rheumatic genesis of mitral stenosis, which is observed in the prevailing majority of patients, only a small percentage of cases manage to detect typical post-traumatic signs. The average duration of the latent period from acute rheumatic attack to the formation of narrowing of the mitral orifice with severe cardiohemodynamic disorders is one decade. Acute debut of the disease is observed only in the case of atrial fibrillation and in this case there is a rapidly progressive course and the development of disability in a short time.
In the case of a severe course of mitral stenosis, a primary objective examination of the patient already makes it possible to suspect the presence of a blemish, since the patient is constantly in the position of orthopnea, and the patient also exhibits characteristic skin changes in the form of acrocyanosis and the appearance of a bluish blush in the projection of the zygomatic areas on both sides. High pulmonary hypertension is manifested by the appearance of increased presystolic pulsation of the veins in the neck region, and when combined with a tricuspid valve deficiency, signs of a positive vascular pulse are revealed.
The peculiarity of mitral stenosis is the appearance of changes in the objective study of the patient. Thus, palpation of the chest allows us to detect a sharp weakening of the apical impulse due to the displacement of the left ventricle by the hypertrophied right ventricle of the heart. Expressed myocardial hypertrophy of the right heart can be accompanied by visual pulsations under the xiphoid process of the sternum, which increases with deep inspiration.
In order to diagnose hemodynamic disorders in mitral stenosis, it is recommended that specific palpation be performed with the determination of voice jitter in a horizontal position with a turn to the left side. The pronounced narrowing of the mitral orifice is accompanied by a symptom of "enhanced diastolic vocal tremor" in the projection of the apex of the heart.
An experienced cardiologist, using the auscultative method of examining a patient, can reliably establish a diagnosis, since this pathology is accompanied by specific auscultative changes. So, due to the limited filling of the cavity of the left ventricle with blood, there is a "clapping" 1 tone. The pronounced calcification of valve flaps limits their motor activity, as a result of which the sonority of 1 tone is sharply weakened. When listening to the heart in the horizontal position of the patient, there may be a "click of the opening of the mitral valve" at the listening point of the apex of the heart. The appearance of a 2-tone accent in the projection of auscultation of the pulmonary artery indicates the development of pulmonary hypertension due to lengthening of the systolic contraction of the right ventricle.
Diastolic murmur is heard both in the variant of the presystolic and mesodiastolic, and its duration depends directly on the severity of the stenotic constriction of the mitral orifice. The best point of auscultation of diastolic noise is the projection of the apex of the heart during the delay in breathing during the exhalation phase. Atrial fibrillation, which often accompanies mitral stenosis, contributes to the disappearance of the presystolic component, up to the complete absence of diastolic noise.
Degrees of mitral stenosis
Classification of mitral stenosis by stages and degrees of severity is used in connection with the fact that each degree of disease requires the use of a particular method of treatment in order to normalize the functional state of the patient.
• The first or initial degree of mitral stenosis indicates complete safety of the compensatory capabilities of the patient's cardiovascular system. Compensatory mechanisms consist in a slight increase in pressure in the cavity of the left atrium to a level of 10 mm Hg. and an increase in its systolic contraction with a mitral opening exceeding 2.5 cm 3 . In the initial stage of the disease, the patient's ability to work is fully preserved, and patients do not notice a significant health disorder. However, when performing radiation diagnostic methods, signs not only of dilatation of the left atrial cavity, but also an increase in its wall are found.
• Subcompensatory or second degree of mitral stenosis is characterized by the inclusion in the compensatory mechanisms of enhanced right heart function, namely, the right ventricle. At this stage, the formation of the so-called "first barrier" is noted in the form of a pronounced narrowing of the mitral opening to 1.5 cm 3 . Also at this stage there is a more significant increase in the blood pressure gradient in the left atrium to 30 mm Hg. to maintain the cardiac output at a constant normal level. An increase in the pressure gradient in the pulmonary capillary network is accompanied by the appearance in patients of characteristic complaints of dyspnea in conditions of increased physical activity, episodic attacks of hemoptysis and cardiac asthma . Instrumental diagnostic methods allow to identify in this category of patients signs of congestion of the right heart and pulmonary hypertension. The incapacity of the patient with a second degree of mitral stenosis is somewhat limited, but preserved.
• Symptoms observed in the third degree of mitral stenosis are caused by the formation of a pathogenetic "second barrier", which is accompanied by the development of progressive right ventricular failure and persistent pulmonary hypertension in the system of arterial vessels. Patients with a third degree of mitral stenosis belong to the category of patients with an unfavorable prognosis for rehabilitation, but life expectancy in this situation can reach several decades provided that an adequate scheme of drug therapy is selected.
• The peculiarity of the fourth degree of mitral stenosis, indicative of the progression of the disease, is a sharp increase in myocardial function and persistent hemodynamic disorder. An interesting fact is that the size of the mitral orifice can be the same as in the third degree, but progressive pulmonary hypertension with organic changes in the pulmonary parenchyma greatly worsen the course of the underlying disease. A typical specific symptom that characterizes the transition of mitral stenosis to the fourth stage is the appearance of atrial fibrillation in the patient. Patients with a fourth degree of mitral stenosis have unfavorable prognosis for life, and as a rule, the lethal outcome of the disease develops within a few months.
• Fifth, or terminal degree is characterized by the appearance of irreversible dystrophic disorders in the circulatory system.
There is no clear gradation and timing of the duration of any stage of mitral stenosis, but there is a clear dependence of the course of the disease on the timeliness of the diagnosis of the defect and the provision of an appropriate pathogenetically justified volume of therapeutic measures.
Provided there are no necessary systematic medical measures or their inconsistency in the severity of the patient's condition, conditions are created for the development of life-threatening patient conditions. So, complications of mitral stenosis are observed even at the third degree of the defect and are manifested in the form of such pathologies:
- alveolar type of pulmonary edema (observed during the initial manifestations of the disease and extremely rare in severe stages of mitral stenosis);
- rhythm disturbances (most often there is a persistent form of atrial fibrillation, and the mechanism of its occurrence is due to mass death of cardiomyocytes and the appearance of sclerotic changes in the myocardium);
- thromboembolic lesions of cerebral vessels;
- infectious disease of the bronchopulmonary apparatus as a result of prolonged stagnant changes;
endocarditis of infectious nature.
Treatment of mitral stenosis
In a situation where the clinical manifestations of mitral stenosis are completely absent, the medicamentous measures are aimed at preventing infectious complications, and, if necessary, on the implementation of course bicillin prophylaxis in the rheumatic genesis of the defect.
Among non-pharmacological methods of correction of hemodynamic disorders, a certain limitation of physical activity and correction of eating behavior are recommended with the complete exception of consumption of table salt and liquid. If mitral stenosis is in the initial stage of development and is accompanied by attacks of atrial fibrillation, prolonged use of Digoxin is recommended for the purpose of reducing the number of cardiac contractions.
In cases of episodic hemoptysis and thromboembolization of the lumen of the pulmonary arteries, it is advisable to conduct active anticoagulant therapy with Heparin and subsequent transition to indirect anticoagulants.
An effective method of arresting atrial fibrillation is an electroimpulse type defibrillation, however this manipulation requires preliminary anticoagulant preparation of the patient within 1 month. The expressed mitral stenosis in a combination with disturbance of a rhythm of heart activity is not subject to electropulse therapy. In this case, one resorts to transthoracic depolarization only after surgical treatment of the defect.
The most effective treatment for correction of hemodynamic disorders with stenosis of the mitral orifice is surgical correction of the defect. The main operational benefits in this case include: mitral valvulotomy and valve prosthesis. Before determining the method of surgical treatment, the patient must be carefully examined, in order to determine the morphological type of the defect and the depth of hemodynamic disorders. In addition, when choosing a particular surgical intervention, it is necessary to take into account the age of the patient and the technical capacity of the medical institution.
In a situation where there is "pure mitral stenosis", not accompanied by calcification of the valvular apparatus, the preferred surgical method is valvulotomy. If, after the operation, the patient has symptoms of the disease, then restenosis of the mitral valve or damage to the structure of other heart valves should be suspected.
If valvulotomy is not accompanied by a persistent positive result and the patient retains hemodynamic disorders characteristic of mitral stenosis, it is advisable to perform valve prosthesis using a mechanical or biological implant. The mortality rate of patients in the postoperative period does not exceed 10% and directly depends on the presence or absence of severe right ventricular failure. The installation of the bioprosthesis provides for further calcination of its flaps, and in this connection, in a few years the patient should perform an implant replacement.