Congenital aortic stenosis in children

Introduction to congenital aortic stenosis in children Congenital aortic stenosis (CAS), which is the sixth in the incidence of congenital heart disease, is a variety of malformations in the embryonic aortic valve, such as single leaf, double leaf, three leaf Or four-leaf petal, the most common with double-leaf flaps. The leaflets are thickened and the annulus is poorly developed, resulting in a narrowing of the valve. basic knowledge The proportion of illness: the probability of illness in infants and young children is 0.49% Susceptible people: children Mode of infection: non-infectious Complications: pulmonary edema, patent ductus arteriosus, aortic valve insufficiency

Causes of congenital aortic stenosis in children

(1) Causes of the disease

Adult aortic stenosis is mostly rheumatic or arteriosclerotic, while aortic stenosis in children is congenital. More than half of valvular stenosis is a two-leaf aortic valve, followed by valve leaf adhesion, thickening or fusion. It has a conical shape with a small hole in the center and a diameter of 2 to 4 mm. Although this type rarely has intracardiac malformation, it is often accompanied by aortic coarctation or patent ductus arteriosus. Infants with severe aortic stenosis, aorta The development of the ring may be poor, resulting in left ventricular dysplasia and aortic valve development disorders and atresia. Children's aortic valve stenosis rarely secondary to valvular calcification, but adult congenital aortic stenosis can eventually be due to blood flow impact. Caused by leaflet thickening and calcification, subvalvular stenosis can be divided into localized subaortic stenosis and hypertrophic subvalvular stenosis, hypertrophic subvalvular stenosis belongs to the category of idiopathic cardiomyopathy, localized subvalvular stenosis Caused by the left ventricular outflow tract flap 0.5 ~ 1.0cm with an annulus fibrosus or narrow and long fibrous musculature caused by stenosis, infantile subvalvular stenosis often offset from the ventricular exit interval into the left ventricular outflow Cause, and multi associated with coarctation of the aorta or aortic arch, rarely diagnosed,

(two) pathogenesis

Pathological classification

There are three types of stenosis type, the most common type is the hourglass type, which is characterized by thickening of the middle layer of the aorta and structural disorder. A narrow annular sac is formed on the upper edge of the aortic sinus; Followed by a diaphragm type, a semi-annular diaphragm formed by fibrous or fibrous muscle tissue that extends into the aortic lumen. All types of ascending aorta are all dysplastic, patients with this disease due to left ventricular discharge obstruction, intraventricular systolic pressure must be increased, in order to maintain a roughly normal circulating pressure, severe left ventricular systolic pressure up to 200 ~ 250mmHg (28.0 ~ 33.3kPa) The left ventricular contraction time is prolonged, the wall is thickened, the aortic pressure is lower after stenosis, the pulse pressure is slightly reduced, the coronary artery opening may be narrowed, or the diastolic coronary artery perfusion time is relatively shortened, and the systolic period is passed. The rapid blood flow in the stenotic valve causes the suction phenomenon, which makes the coronary blood supply insufficient.

2. Pathophysiology

The hemodynamic changes of aortic stenosis are blocked by left ventricular dysfunction. The severity of pathophysiological changes depends on the degree of stenosis of the valve. Due to aortic stenosis, the resistance of left ventricular ejection increases, in order to maintain normal output and Blood pressure, compensatory increase in left ventricular contractility, increased ventricular wall tension during ejection, prolonged systole, increased myocardial work, increased myocardial metabolism and oxygen consumption, coronal hypertrophy due to left ventricular wall, increased oxygen consumption and coronary The blood supply to the arteries cannot be increased correspondingly, but the reasons are:

(1) The opening of the coronary artery is also narrow.

(2) The diastolic time limit is relatively shortened, and the coronary perfusion time is shortened.

(3) Left ventricular systolic hypertension causes the coronary artery wall to be squeezed by the myocardium, increasing the resistance to perfusion.

(4) systolic blood flow through the aortic valve at high speed, the suction effect caused by the Ventyri effect reduces the blood perfusion of the coronary artery. For various reasons, the hypertrophic myocardial blood supply is seriously insufficient, left ventricular myocardium or intracardiac Ischemia and necrosis occur under the membrane, leading to heart failure and even sudden death.

Prevention of congenital aortic stenosis in children

Ask family history to understand the genetic situation, investigate the impact of environmental factors to explore the cause of congenital heart disease, Shaw through the investigation of the address to understand the environmental teratogenic factors that the pregnant mother may be exposed, the address of the mother's production is sometimes used to represent The address of the early pregnancy was estimated by environmental factors. The authors investigated the address of the mother at the time of pregnancy and birth. About 24.8% of the mothers moved between the beginning of pregnancy and production, so observing the production address may reduce congenital malformation and the mother's exposure to the environment. The positive result of the association should be investigated in the environment of the address at the time of pregnancy. Schwanitz advocated that the detection of cardiac malformation before birth can be used as an indication for chromosomal examination. The authors mentioned that 588 fetuses were diagnosed with growth retardation and/or congenital malformation before birth. A chromosomal examination was performed, and 116 (19.7%) of these cases were shown to have chromosomal abnormalities in these malformed fetuses diagnosed before birth.

There are 102 (17.3%) fetuses with cardiac malformations. Therefore, cardiac malformation is the most common malformation. Of the fetuses diagnosed with cardiac malformations before birth, 41 fetuses (40.2%) have chromosomal abnormalities (18 and 21 Trisomy is the most common syndrome. In addition to monitoring the fetus, the mother's disease should also be monitored. Breton reported that the mother had phenylketonuria, and the plasma phenylalanine increased continuously during pregnancy. The child born with a heart malformation, Breton reported that a child's coronary artery originated from the right pulmonary artery, ventricular septal defect, fetal growth retardation and facial deformity, and his mother's plasma phenylalanine continued to increase during pregnancy, cardiac malformation in It is diagnosed 8 months after birth, and its developmental delay is caused by maternal phenylketonuria, which can also cause ventricular septal defect and coronary artery malformation. The authors suggest that if the mother begins dietary treatment before pregnancy, it may prevent it. Damage to the fetus, therefore, if there is a deep understanding of the cause, mothers and fetuses can be monitored for pregnancy and fetus before pregnancy. It is possible to do our utmost to prevent fetal congenital malformations. However, from the perspective of genetics and environmental damage, the cause of congenital heart disease is not fully understood, and most of them are powerless in prevention, so explain The cause and the fundamental prevention of congenital heart disease are still an extremely difficult task, and scholars in clinical and basic fields need to work together to explore.

Complications of congenital aortic stenosis in children Complications pulmonary edema, patent ductus arteriosus, aortic valve insufficiency

In patients with aortic stenosis, left ventricular hypertrophy, systolic function is generally normal. Patients with severe aortic stenosis may have left ventricular dilatation and systolic dysfunction. Due to left ventricular hypertrophy, left ventricular compliance decreases, mitral flow E/A <1, due to cardiac hypertrophy, insufficient coronary blood supply, can cause myocardial Ischemia, papillary muscle necrosis, endocardial elastic fiber hyperplasia, mitral regurgitation, combined with heart failure, ventricular fibrillation or acute pulmonary edema, common aortic stenosis with patent ductus arteriosus (20 %65%), aortic coarctation (11%53%), mitral valve abnormality (25%), pulmonary stenosis, aortic stenosis, endocardial fibroelastosis, aortic arch disconnection and main Insufficient arterial regurgitation.

Congenital aortic stenosis in children Symptoms Common symptoms Pre-cardiac pain relief systolic murmur systolic tremor heart failure fatigue dyspnea sudden death

General symptoms

The disease is more common in men, the severity of the symptoms depends on the degree of stenosis, such as stenosis more than 25% of the normal area of the aortic orifice, that is, the aortic orifice can reduce symptoms when the child is reduced to 0.6cm2, such as developmental disorders, fatigue, breathing Difficulties, fainting, pain in the precordial area, heart failure and even sudden death, generally no symptoms, no bruising and difficulty breathing.

2. Cardiac examination

The size of the heart is normal or enlarged. In the second intercostal space of the right sternal border or the third and fourth intercostals of the left rim, the systolic tremor is twitched, and the III-IV rough jetting murmur is heard, and the rhythm is on the heart sound map. The right neck, back, apex and even elbow conduction, sometimes in the aortic valve area can still hear the early contraction of the contraction, the second heart sound of the aortic valve area is normal or weakened, if the aortic stenosis, accompanied by aortic valve When the closure is incomplete, there is a high-pitched diastolic murmur in the aortic valve area, and the peripheral arterial pressure is normal or decreased. If the stenosis is severe, the pulse pressure is reduced compared with normal.

Examination of congenital aortic stenosis in children

General routine inspections are normal.

X-ray inspection

The shape of the heart is normal or enlarged, and the left ventricle is mainly enlarged. The contraction is strong under fluoroscopy. The ascending aorta is also widened due to the expansion after stenosis. The left atrium is enlarged in the right anterior oblique position during meal.

2. ECG examination

Normal or showing left ventricular hypertrophy with myocardial strain, I, II lead and pre-cardiac lead V5, V6, visible T wave inversion.

3. Echocardiography

The active valve waveform between the aortic root curves can not see the normal opening and closing, showing a thick curve, synchronous movement with the root curve, sometimes visible open, but the separation is small, the diameter of the ascending aorta and the valve The horizontal aortic root diameter is relatively small, the left ventricular wall and interventricular septum thickening is obvious, and the Doppler technique can be used to estimate the transvalvular pressure difference.

4. Cardiac catheterization

Right heart catheterization is not helpful. It only shows pulmonary microvasculature, pulmonary artery and right ventricular pressure are increased. Left ventricular catheterization shows that the ascending aorta or peripheral arteries have lower systolic blood pressure and left ventricular systolic blood pressure. The pressure difference between the two is obvious. The aortic orifice is stenotic, the peripheral arterial pressure curve rises slowly, the ascending branch has a notch, and the left ventricle angiography shows the location and extent of the left ventricular wall thickening and aortic stenosis.

5.CT and MRI

CT and MRI examinations are helpful in the diagnosis of aortic stenosis. MRI spin echo T1W images can show aortic valve thickening, left ventricular centripetal hypertrophy, ascending aortic stenosis and other changes, gradient echo movie sequence It can be seen that the abnormal blood flow of the low signal is injected into the ascending aorta. The flow rate measurement can also estimate the magnitude of the pressure gradient caused by aortic stenosis. The gradient echo movie sequence can also accurately measure the left ventricular end-diastolic volume. And left ventricular ejection fraction, if there is aortic regurgitation, low signal abnormal blood flow can be seen in the left ventricle, contrast-enhanced magnetic resonance angiography sequence and multi-slice spiral CT show better expansion after ascending aortic stenosis. It is helpful to identify aortic stenosis and other diseases that cause ascending aortic dilation.

6. Cardioangiography

Cardiac angiography of aortic stenosis usually begins with left ventricular angiography, severe aortic stenosis, because the catheter is retrograde through the narrow aortic valve is quite difficult, you can do ascending aortic angiography, observe the direction of the jet and the presence or absence of aortic valve After refluxing, try to send the catheter tip into the left ventricle for left ventricular angiography. Both the ascending aorta and left ventricular angiography catheters select the left tail angiography catheter, and the left anterior oblique or orthotopic position is used. With Omi Parker 350, ascending aorta angiography 1.5ml/kg, left ventricle angiography 1.2ml/kg, normal aortic valve with 3 leaflets, valve sinus also 3, thin leaflets, valvular contraction when the leaflets open, Directly to the edge of the valve sinus, the ascending aorta is more uniform from top to bottom. Cardiovascular angiography in children with congenital aortic stenosis can sometimes diagnose the two-valve deformity. When there are two sinus sinus in the ascending aorta diastolic period The aortic two lobes should be considered. The size of the two sinus sinus is similar or one of them. Not all aortic two-valve deformities can be correctly diagnosed by angiography, and some aortic two-valve deformity is in the angiography. There are three visible sinus node, which is due to two lobes sinus often a fusion of middle seam, the seam is on the deeper-made movie looks like there are three sinus node.

The aortic valve is often thickened, so that the aortic valve that is barely identifiable on the angiogram becomes clearly visible. When the ventricle contracts, the valve cannot be completely opened, and the leaflet forms an arched shape upwards. "Fish stagnation", but dysplastic aortic stenosis does not have this sign, aortic stenosis due to stenosis of the valve, left ventricular angiography can be seen a bundle of contrast agent sprayed from the narrow valve mouth, this sign is called For the "jet levitation", the width of the contrast agent beam reflects the severity of the stenosis of the valve. The jet width is often used to determine the effect of balloon augmentation of aortic stenosis. Ventricular blood is ejected from the stenotic valve. The left ventricular blood dilutes the contrast agent in the ascending aorta to form a transparent capsule called the "negative jet sign", which also has the meaning of the severity of the stenosis. (Fig. 1) In addition to the above signs, left ventricular hypertrophy, ascending aortic stenosis and other manifestations were observed during cardiovascular angiography. Some patients with aortic stenosis were associated with aortic regurgitation, preparing for a balloon Expand In children with aortic stenosis treated, augmented aortic angiography must be performed before and after balloon dilation to see if aortic regurgitation is caused or aggravated by balloon dilation.

Diagnosis and differential diagnosis of congenital aortic stenosis in children

diagnosis

According to clinical manifestations, the systolic murmur of the second intercostal space on the right sternal border and the data of X-ray, electrocardiogram and echocardiography are not difficult to diagnose.

Differential diagnosis

The disease often needs to be differentiated from rheumatic aortic stenosis in clinical practice. Rheumatic aortic stenosis is acquired heart disease, clinical fever, joint pain, laboratory examination has anti-"O" increase, erythrocyte sedimentation rate and other characteristics The onset age of rheumatic fever is more common in 5 to 15 years old, rare under 3 years old, and the time of valvular disease is later. It often needs to be repeated for 6 months to 2 years after carditis, and mainly invades the mitral valve. Because of the obvious murmur and left ventricular hypertrophy, it is necessary to distinguish from ventricular septal defect and patent ductus arteriosus. The identification mainly depends on right heart catheterization.

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