OVERVIEW
Rheumatic mitral insufficiency is characterized by thickening and contracture of the leaflets and tendon cords, reduction of valve area, restricted leaflet mobility, and enlargement of the mitral annulus. Rheumatic mitral insufficiency is more common and is associated with stenosis in more than half of the cases.
Etiology
Rheumatic fever is a dominant factor in the pathogenesis of this disease. There are the following two scenarios:
1. In cases of rheumatic mitral stenosis with closure insufficiency, rheumatic fever causes long-term repeated inflammation of the mitral valve, mitral valve fibrosis, thickening, stiffness, junctional fusion, resulting in stenosis of the orifice, and at the same time, the leaflets are contracted and deformed due to fibrosis, and the free edge of the orifice is curled up due to fibrosis, thickening, or calcium deposits, resulting in the anterior and posterior leaflets not being able to close together in ventricular contraction, and the tendon cable papillary muscles are shortened due to fibrosis and shortening, which can close the leaflets. Fibrosis and shortening of the papillary muscles of the tendon cords pull the leaflets toward the ventricular cavity, thus limiting their mobility and hindering the opening and closing of the valve, resulting in both stenosis and incomplete closure of the mitral valve.
2. In cases of simple mitral valve closure insufficiency, although there is a certain degree of fibrosis and thickening of the valve, there is no fusion of the leaflet junctions, and there is no obstacle to the flow of blood through the mitral valve orifice, and the main lesion is the enlargement of the mitral valve annulus. The mitral annulus thickens with the enlargement of the left ventricle, and the annulus at the base of the posterior leaflet enlarges even more significantly, resulting in a relative leaflet area that is insufficient for systolic valve closure. If the acute phase of rheumatic fever is properly treated, the myocarditis is healed, the left ventricle and the annulus are reduced in size and return to normal, then the closure insufficiency can disappear. If there is no medical treatment or ineffective treatment during the myocarditis stage, the left ventricle and annulus continue to enlarge. After several years, the left ventricle and annulus enlarge further due to mitral valve insufficiency, and the degree of insufficiency increases. The mitral valve leaflets do not align during heart contraction, and the tendon cords are subjected to increased tension and may break. Trauma to the valve leaflets caused by systolic blood impingement on the left ventricle may present as fibromucinous degenerative lesions.
Symptoms.
Mild lesions with good cardiac compensation may be asymptomatic. In severe or long-lasting lesions, symptoms such as fatigue, palpitations, and shortness of breath after exertion may occur. The incidence of acute pulmonary edema and hemoptysis is much lower than that of mitral stenosis. The condition can deteriorate rapidly in a relatively short period of time after the onset of clinical symptoms.
The main sign is an increased apical beat with a downward shift to the left. A holosystolic murmur can be heard in the apical region, often traveling to the left midaxillary line. The second tone in the pulmonary valve area is hyperactive and the first tone is diminished or absent. Advanced cases may present with right heart failure as well as signs of hepatomegaly and ascites.
Examination
1. Electrocardiography
In mild cases, the electrocardiogram may be normal. In more severe cases, it often shows left deviation of electrical axis, mitral P wave, left ventricular hypertrophy and strain.
2. X-ray examination
The left atrium and left ventricle are obviously enlarged. X-ray examination with barium swallow shows that the esophagus is shifted backward by pressure.
3. Echocardiography
M-mode examination shows a bimodal or unimodal mitral valve curve, with an increased rate of rise and fall. The anterior and posterior diameters of the left ventricle and left atrium are significantly enlarged. The posterior wall of the left atrium shows a pronounced wave of depression. In cases of combined stenosis, a rampart-like rectangular wave may still be seen. Two-dimensional or cross-sectional echocardiography directly demonstrates the failure of the mitral valve orifice to close completely during cardiac contraction. Echocardiographic Doppler testing shows diastolic blood turbulence, which can be used to estimate the severity of the closure insufficiency.
4. Cardiac catheterization
Right heart catheterization may show elevated pulmonary artery and capillary pressures and decreased cardiac output index.
5. Left ventriculography
Contrast agent is injected into the left ventricle and can be seen to flow back into the left atrium during cardiac contraction. If the degree of insufficiency of closure is severe, the contrast reflux is high. However, the left ventricular excretory fraction is reduced.
Diagnosis
The combination of clinical features and appropriate investigations may assist in the diagnosis.
Differential Diagnosis
The murmur of mitral insufficiency should be differentiated from the systolic murmur in the apical region of the heart in the following conditions:
1. Relative mitral valve closure insufficiency
It can occur in hypertensive heart disease, aortic valve insufficiency due to various causes or myocarditis, dilated cardiomyopathy, and anemic heart disease. As the left ventricle or mitral annulus is significantly enlarged, the relative closure of the mitral valve is incomplete and an apical systolic murmur occurs.
2. Functional apical systolic murmur
The systolic murmur can be heard in about half of normal children and adolescents, and it is short, soft, and does not mask the first heart sound, with no atrial or ventricular enlargement. It can also be seen in fever, anemia, hyperthyroidism and other hyperdynamic circulatory states, and the murmur disappears when the cause is eliminated.
3. Ventricular septal defect
A rough systolic murmur, often accompanied by systolic tremor, can be heard in the 3rd to 4th intercostal space at the left edge of the sternum, and the murmur is transmitted to the apical region, and the apical beat is lifting-like. Electrocardiogram and X-ray showed enlargement of the right and left ventricles. Echocardiography shows continuous interruption of the interventricular septum, and acoustic imaging confirms the presence of left-to-right shunting at the ventricular level.
4. Tricuspid valve insufficiency
A limited wind-blowing holosystolic murmur is heard at the lower end of the left sternal border. The murmur is augmented by the increase in regurgitant blood volume during inspiration and diminished during expiration. In pulmonary hypertension, the second heart sound of the pulmonary valve is hyperactive, and the jugular vein v-wave is enlarged. The liver may be pulsatile and enlarged. Right ventricular hypertrophy is seen on ECG and X-ray. Echocardiography can clarify the diagnosis.
5. Aortic stenosis
A loud, coarse systolic murmur can be heard at the base of the heart in the aortic or apical region, traveling toward the neck with systolic tremor. There may be early systolic clicks and a lifting apical beat. Left ventricular hypertrophy and enlargement can be seen on ECG and X-ray. Echocardiography can clarify the diagnosis.
Treatment
The symptoms of mitral valve insufficiency are obvious when the cardiac function is affected and the heart is enlarged, then direct vision surgery under extracorporeal circulation should be carried out in a timely manner. Surgical methods can be divided into two types:
1. Mitral valve repair and molding
Repair of the mitral valve using the patient’s own tissues and some artificial substitutes to restore its function, including reconstruction and reduction of the annulus, shortening or lengthening of the papillary muscles and tendon cords, implantation of an artificial annulus and tendon cords, and repair of the valve leaflets. The surgical technique is complex, and the results of the repair should be examined intraoperatively to see if the insufficiency of closure has been corrected; if the insufficiency of closure is still evident, then mitral valve replacement should be performed again.
2. Mitral valve replacement
Mitral valve replacement is required in cases where the mitral valve is severely damaged and not amenable to valve repair. The mitral valve leaflets and tendon cords are removed, but 0.3 to 0.5 cm of leaflet tissue is retained along the annulus, and the prosthesis is sutured to the annulus. There are two major types of prosthetic valves used in clinical practice: mechanical valves and biological valves. Each has its own advantages and disadvantages and should be used according to the situation. Heart valve replacement is more effective, but correct postoperative treatment is very important, such as the maintenance of cardiac function, anticoagulation therapy after mechanical valve replacement, long-term follow-up and treatment of patients.