congenital subaortic stenosis
Introduction
Introduction to congenital subaortic stenosis In cases of subaortic stenosis, the aortic valve is mostly normal, showing a three-valve type. In some cases, the leaflets are slightly thicker or have mild regurgitation. A small number of patients can have a double-valve aortic stenosis. Left ventricular myocardium presents a highly concentric hypertrophy, and subendocardial blood supply can cause myocardial fibrosis. Sometimes the ventricular septal myocardial hypertrophy is more significant than the left ventricular posterior wall, which is easily confused with obstructive hypertrophic cardiomyopathy. About 1/3 of the aortic stenosis is associated with other congenital vascular malformations. Ventricular septal defect, aortic arch interruption, patent ductus arteriosus, tetralogy of Fallot, atrial septal defect, pulmonary stenosis or right ventricular stenosis. basic knowledge The proportion of illness: 0.001% Susceptible people: no special people Mode of infection: non-infectious Complications: aortic regurgitation, endocarditis, sudden death
Cause
Causes of congenital subaortic stenosis
Cause:
Aortic subvalvular stenosis accounts for 20% to 25% of obstructive lesions of the left ventricular outflow tract, which can be caused by congenital factors or abnormal myocardial hypertrophy (primary or secondary). Congenital subaortic stenosis is a rare congenital Malformation, which accounts for 0.5% of congenital heart disease. Under normal development, most of the heart is degenerated, and the left part is integrated into the right ventricular funnel. If the heart fails to degenerate for any reason, the valve is produced. Lower obstruction, Edwards [4] in 1965 has a detailed description of its pathological mechanism, Reis et al. believe that congenital subaortic stenosis may be inherent or hypertrophic, the former case is divided into localized subvalvular stenosis, tube There are three types of subvalvular stenosis and mitral valve malformation. The limited subvalvular stenosis is further divided into localized membranous stenosis and fibromuscular stenosis. It is also proposed to divide the left ventricular outflow tract obstructive lesion into three anatomical types. That is, the membrane type, the fiber muscle ring type and the tube type, the stenosis caused by abnormal hypertrophy of the myocardium may be originally caused by the myocardial lesions, such as hypertrophic cardiomyopathy, or the aortic valve and the obstruction caused by various causes. Lesions, their pathology, local anatomical patterns, surgical treatment and The therapeutic effect is different from the congenital aortic stenosis.
Prevention
Congenital prevention of subaortic stenosis
Depending on the degree of aortic stenosis, mild stenosis, good prognosis, can live to the elderly, but can be complicated by subacute bacterial endocarditis, severe stenosis increases with age, stenosis, and more than childhood Myocardial hypoxia, ventricular fibrillation and death, as a result of death due to left ventricular failure, rare in infants with aortic stenosis, died of heart failure.
Complication
Congenital complications of subaortic stenosis Complications aortic valve insufficiency endocarditis
The disease can be complicated by aortic regurgitation and is complicated by endocarditis.
1, aortic valve insufficiency
Left ventricular diastolic phase in patients with aortic regurgitation undergoes left atrial blood while additionally receiving blood from the aorta, resulting in progressive increase in left ventricular end-diastolic volume, and left ventricular compensatory mechanism with myofibrils , produces eccentric left ventricular hypertrophy, increased left ventricular compliance, gradually adapts to chronic left ventricular chronic volume overload, ensures left ventricular end-diastolic volume increase and left ventricular end-diastolic pressure in the normal range, this myocardial compensation mechanism can be maintained For a long time, the patient is asymptomatic, but as the disease progresses, the ventricular wall hypertrophy is aggravated. The left heart is mainly in the subendocardial area. With left ventricular systolic and diastolic dysfunction, symptoms appear and the left ventricular function is fast. Reducing is irreversible; therefore, such patients often fail to see a doctor for a long period of time due to myocardial compensatory mechanisms because of no symptoms. Once symptoms appear, they quickly cause irreversible changes in left ventricular function, even Surgery, the prognosis is relatively poor, a considerable number of patients have no clear history of rheumatic activity, general aortic regurgitation Between 7 and 10 years, the reflux gradually increased. Initially, the diastolic blood pressure of the left atrium and the left ventricle did not increase. After clinical activities, palpitations or dyspnea, apical beats and signs of increased carotid pulsation, most patients found the heart during physical examination. Noise and asymptomatic, if there are significant symptoms after general activities, suggesting that the disease is further worsened, angina and left heart failure often occur due to hypertrophic myocardial ischemia in the late stage of the disease, and patients with advanced disease often have sleep disturbance and nocturnal paroxysmal dyspnea at night. More nightmares, increased heart rate, flushing, chest pain or headache with paroxysmal hypertension. People with severe heart failure and angina often die at night. In addition, patients are sweaty and unable to resist heat.
2, endocarditis
Infective endocarditis refers to an inflammatory disease caused by pathogenic microorganisms directly invading the endocardium, and a thrombus (sputum) formed on the surface of the heart valve contains pathogenic microorganisms.
Acute bacterial endocarditis: usually with sudden high fever (39 ~ 40 ° C), increased heart rate, fatigue, rapid and serious valvular damage as the first symptom, endocardial neoplasm (embolism) falling off with blood flow to the body Other parts, resulting in infection of these parts, pus accumulation in the base of the infected valve and the embolic embolism embolization, short-term (days) heart valve perforation and severe blood reflux, some people have shock, kidney Severe dysfunction with other important organs (this state is called sepsis syndrome), intra-arterial infection causes the arterial wall to weaken, can cause arterial rupture, life-threatening (especially when it occurs in the intracranial or proximal aorta) .
Subacute bacterial endocarditis: symptoms can exist for several months before a patient's heart valve damage or embolism is diagnosed by a doctor. Symptoms include fatigue, mild fever (37.5 to 38.5 ° C), weight loss, and sweating. And red blood cell count is reduced (anemia). For people with unexplained fever, if there is a new murmur in the heart, or the nature of the previous murmur changes, it is often suspected that endocarditis is present. It is found that the spleen grows and the skin may appear similarly tiny. Small spots like freckles; the same spots may also appear on the sclera (white eye) or under the bed of fingernails. In fact, these spots are small areas of bleeding, consisting of tiny emboli that fall off the heart valve. As a result, larger emboli can cause abdominal pain, sudden blockage of upper or lower extremity arteries, acute myocardial infarction, and stroke.
Other symptoms of acute and subacute bacterial endocarditis include: chills, joint pain, pale skin, rapid heartbeat, subcutaneous pain nodules, confusion, and hematuria.
Symptom
Congenital symptoms of subaortic stenosis Common symptoms Shrinking early Karayin chest tightness Congenital heart conduction calcification
Aortic subvalvular stenosis does not produce severe left ventricular obstruction in infants and young children, and the clinical symptoms are not serious. Therefore, it is rarely necessary to perform surgical treatment in infants and young children, but in childhood, obstructive lesions develop more rapidly due to The impact of blood turbulence after stenosis, aortic valve leaflets tend to thicken, resulting in aortic valve insufficiency, and easy to end with endocarditis.
Aortic subvalvular stenosis accounts for approximately 25% of congenital aortic stenosis, and two types are common:
(1) Fiber diaphragm type: There is a membrane annular fibrous tissue about 1 cm below the aortic annulus, and some or all of the left ventricular outflow tract blood flow must enter the aorta through the center of the diaphragm or a side of the diaphragm, causing blood. Flow obstruction, in a few cases there is fibrous adhesion between the fibrous septum and the aortic valve leaflet or between the anterior mitral valve leaflets.
(2) aortic subvalvular fiber tunnel stenosis: this type is less common, accounting for about 20% of the aortic stenosis, fibrous tissue is duct-like, extending downward from 1 to 2.5 cm below the aortic annulus In the distal segment of the left ventricular outflow tract, the fiber tube generally has an inner diameter of about 1 cm and a length of from 1 cm to 3 cm. The elderly of the tube often has a narrow aortic annulus and a heavy blood flow obstruction.
Type of subaortic stenosis:
(1) fiber tunnel type stenosis; (2) fiber diaphragm type stenosis.
Clinical manifestations of subaortic stenosis: X-ray, electrocardiogram, and cardiac catheterization were similar to aortic valve stenosis, but rarely heard early contraction, and mitral anterior leaflet mobility was limited by fiber stenosis In the apical area, the middle diastolic murmur caused by mitral regurgitation can be heard. The ascending aorta of the chest X-ray is generally not enlarged after stenosis, and there is no calcification of the aortic valve leaflets. In a few cases, the left heart catheterization is continuous. The left ventricular outflow tract and aortic pressure curves were recorded. It is possible that the left ventricular outflow tract recorded the same systolic blood pressure as the aorta. The diastolic pressure was the same as the left ventricle, and a third pressure curve between the left ventricle and the aorta.
Selective left ventricular angiography may show an annular diaphragm-type stenosis with a short localized left ventricular outflow tract, or a longer tunnel-type stenosis.
Two-dimensional echocardiography: The left ventricular long-axis view directly shows the fibrous septum about 1 cm from the aortic annulus and the central part of the aortic valve or the left ventricular outflow tract shows a longer fibrous tubular stenosis The posterior wall of the stenosis is the mitral anterior leaflet.
Examine
Examination of congenital subaortic stenosis
1, X-ray chest radiograph can indirectly reflect the aortic valve or left ventricular outflow tract obstructive lesions, a series of chest X-ray examination can observe the progressive process of hemodynamic progression of congenital subaortic diaphragm stenosis.
2, echocardiography can observe the aortic valve opening and closing movement, the position of the subvalvular stenosis and the degree of left ventricular outflow tract stenosis (pressure difference), but when combined with aortic valve disease or subvalvular stenosis adjacent to the aortic valve, then Echocardiography has an increased chance of missed diagnosis or failure to diagnose.
3, conventional cardiac catheterization and angiography can also observe the aortic valve opening and closing movement, subvalvular stenosis and left ventricular outflow tract stenosis (pressure difference), but found direct signs of subvalvular septal stenosis - low density The ability of negative filling signs is also affected by the local anatomy of the diaphragm type stenosis, and its effect is not even as good as echocardiography.
4, non-invasive or less invasive EBCT, with high time resolution, can effectively eliminate the movement artifacts of the cardiovascular system, truly realize the "real-time" imaging of the sports heart, the partial anatomical display of the cardiovascular system And functional assessment provides accurate and objective diagnostic information, less subjective to the operator's subjective experience, and the film scan not only clearly shows the movement of the aortic valve and diaphragm, but also accurately reflects its left ventricular outflow tract. Effects and hemodynamic changes: ventricular function and wall changes, EBCT is superior to the above-mentioned imaging methods in the display of local anatomical details under the aortic valve. Therefore, the diagnosis of clinical congenital cardiovascular malformations and the observation of surgical outcomes And during follow-up, EBCT has a high clinical value.
Diagnosis
Diagnosis and diagnosis of congenital subaortic stenosis
Because of the obvious murmur and ventricular hypertrophy, the disease needs to be differentiated from ventricular septal defect and patent ductus arteriosus. The identification mainly depends on cardiac catheterization.
1, ventricular septal defect: right heart catheterization, determination and comparison of blood oxygen content in the right heart chamber, such as the right ventricle is 1.0% by volume higher than the right atrium, indicating that the ventricular level has left to right shunt; less flow Small caliber defect, or defect caliber is not small, but there is obvious pulmonary hypertension caused by left to right sub-flow reduction, right ventricular / right atrial oxygen difference is often less than 1.0% by volume, suspected of this situation, should Adding hydrogen absorption test, compare and observe the time of hydrogen ion curve appearing in the right heart chamber, such as the right ventricle is more advanced than the right ventricle, indicating that the ventricle level has left to right shunt; severe pulmonary hypertension, ventricular level is two-way or anti- To the diverter, the right ventricle, the right room has no edema, can be verified from the different degrees of decline in the measured arterial oxygen saturation, the right heart chamber (especially continuous measurement of pulmonary artery and right ventricle) pressure If the right ventricular pressure significantly exceeds the pulmonary artery pressure, according to the characteristics of the pressure curve, it can be combined with the right ventricular outflow tract or / and pulmonary stenosis; generally the pulmonary artery pressure is determined by the ratio of pulmonary artery pressure to body arterial pressure. The degree of elevation, <40% is mild, 40-70% is moderate, and >70% is severe. According to pulmonary artery pressure and cardiac output index, the pulmonary vascular resistance is converted, which is helpful for the timing of surgery. Selection and surgical indications and contraindications are judged to calculate the ratio of pulmonary circulation to systemic blood flow and the ratio of the two, generally with a low flow of <1.3, a medium flow of 1.3 to 2.0, and a high flow of >2.0.
2. Patent ductus arteriosus: Cardiac catheterization and selective indicator dilution curve The main finding of right heart catheterization is that the blood oxygen content of the pulmonary artery is higher than the blood oxygen content of the right ventricle by more than 0.5% by volume, and the pulmonary blood flow is increased. The right ventricular pressure may be normal or slightly increased. The cardiac catheter may enter the descending aorta through the patent ductus arteriosus. The pulmonary artery pressure may be increased by bidirectional or right to left shunt. At this time, the arterial blood oxygen content, especially the lower limbs. The arterial blood oxygen content is reduced. In patients with a small left-to-right partial flow of the patent ductus arteriosus, a cardiac catheter with a platinum electrode can be placed in each part of the right heart and the pulmonary artery. The patient inhales hydrogen as a hydrogen dilution curve to find that At this time, the pulmonary artery level curve arrives earlier, and the arrival time is shorter than 4 seconds.
