Atrioventricular canal malformation

Introduction The atrioventricular tube defect has been called endocardial pad defect, the first hole type defect, the atrioventricular common tract, or the primary hole defect is a series of congenital heart malformations formed by the first septum and endocardial dysplasia. The main lesions are partial loss of the atrioventricular ring, the lower atrium, and the ventricular septal tissue, and may be associated with varying degrees of atrioventricular valve malformation. Atrioventricular tube malformations are rare, accounting for only 5% of all types of atrial septal defect. The disease is a congenital disease, which is formed by the development of primary atrial septal dysplasia or excessive absorption during embryonic development. Can be divided into partial type of atrioventricular tube malformation and complete type of atrioventricular tube malformation.

Cause

The disease is a congenital disease, which is formed by the development of primary atrial septal dysplasia or excessive absorption during embryonic development. It can be divided into partial type of atrioventricular tube malformation and complete type of atrioventricular tube malformation. The left atrial flow rate of the atrial level is large, and the symptoms appear early and the condition is heavier.

There are many forms of atrioventricular tube malformation, which can be divided into the following types from simple to complex.

1. The first hole type atrial septal defect

Embryonic endocardial pad dysplasia, failed to fully fuse with the first septum, the first hole after birth continued unbroken. The defect was semilunar, the lower margin was the atrioventricular valve annulus, the upper margin was the first lower margin, the coronary sinus opening was located posteriorly above the defect, and the mitral and tricuspid leaflets were normal and the ventricular septum was intact. This type is very rare.

2. Partial room sharing

In addition to the first atrial atrial septal defect, the central part of the mitral valve is not broken. The length of the gap varies from the small free edge of the leaflet to the full-length division of the entire leaflet. The leaflet leaf tissue is crimped at the edge of the cusp and has a chordae attachment. In most patients, the tricuspid valve leaflets are not fissured, the base of the valve leaflets is attached to the ventricular septum, and there is no channel between the ventricle chambers on both sides. The mitral valve leaflet rupture produces insufficiency. When the heart contracts, blood flows back from the left ventricle into the left atrium, and then enters the right atrium through the first atrial septal defect. This type of defect is most common in atrioventricular tube malformations.

3. Complete room sharing

This type of defect is relatively rare, with complex lesions and more morphological variations. The first hole type defect in the lower atrial septum is connected with the ventricular septal defect. The mitral and tricuspid valves are abnormally developed. They can be divided into several small leaflets. The left and right atrioventricular rings communicate with each other. The mitral and tricuspid The valve leaflets are all ruptured, and the normal mitral and tricuspid valves are replaced by the anterior and posterior leaflets of the common atrioventricular ring. The mitral anterior leaflet and the tricuspid valve leaflet may be partially or completely split into two components, and may also be fused into a common anterior leaflet.

The former case is most common. The anterior valve leaflet edge attaches the mitral valve and the tricuspid valve to the two sides of the upper edge of the ventricular septum through a number of short chordae. In rare cases, the anterior leaflet lobes pass through the edge. The tendon is attached to the abnormal papillary muscle of the right ventricle without adhering to the upper edge of the ventricular septum. In addition, the anterior mitral valve leaflet and the tricuspid valve leaflet may also be non-cleaved and merged into a common anterior leaflet. There is no chordae between the valve leaflet and the ventricular septum and the ventricular wall, suspended above the ventricular septal defect. . This situation is also more common.

In the case of complete type of atrioventricular common tract, the chordae tendine is generally shorter than the anterior leaf chordae, and the valvular condyle is poor when the ventricle contracts, the degree of incomplete closure is heavier, and the return flow is large. The left ventricular cavity is generally smaller than the right ventricle.

4. Single atrium

Embryonic atrial septal tissue is not developed and the whole is missing. The heart has only a single atrial cavity and may be associated with leaflet malformation. This type of defect is extremely rare.

Atrioventricular tube malformation may be associated with patent ductus arteriosus, tetralogy of Fallot, pulmonary stenosis and other congenital cardiovascular disease.

an examination

Related inspection

Electrocardiogram Doppler echocardiography

There are several methods of examination that can be used for this disease:

(1) Chest X-ray examination: The chest X-ray findings of the first atrial atrial septal defect were similar to those of the second atrial septal defect with a large defect. In some cases with partial ventricular regurgitation and complete atrioventricular resection, the heart was significantly enlarged, and the left ventricle, right ventricle, and right atrium were enlarged. The pulmonary blood vessels were significantly congested and the pulsation was enhanced. In cases where the pulmonary circulation resistance is significantly increased, the pulmonary vascular shadows in the hilar region are thickened and the vascular shadows around the lung fields are scarce.

(2) Electrocardiogram examination: the PR interval is prolonged. The right ventricle is significantly hypertrophied or presents with incomplete right bundle branch block, the left ventricle is also hypertrophy, and the motor axis is left-biased. The QRS ring of the frontal surface vector diagram is reversed and the main body of the QRS ring moves upwards to the left or even to the right, and the average electric axis is between -30° and -140°. Some authors pointed out that the QRS ring of the frontal heart vector map of some type of atrioventricular common cases showed a reverse needle to the left, and the horizontal surface QRS reversed to the left to the back; the full-type atrioventricular commonalt was the inverse of the frontal QRS. The needle runs to the right and the horizontal surface QRS runs backwards to the right.

(3) Echocardiography: The right atrium, right atrium and pulmonary artery have an increased inner diameter. The movement of the ventricular septum belongs to the contraction of the right ventricle. During the ventricular ejection, the ventricular septum presents a forward movement, that is, contradictory movement. Sectional echocardiography revealed that the lower part of the interatrial septum, the interventricular septum, the mitral anterior leaflet and the tricuspid valve leaflet were normally separated, and the cross formed by the interconnection in the central area disappeared, and the lower part of the interatrial septum and the upper part of the interventricular septum The echo reflection is interrupted and the four heart chambers communicate with each other. The mitral valve advances, and the anterior leaflet approaches the tricuspid valve leaflet during systole and approaches the ventricular septum during diastole. The mitral valve diastolic period is a suspension bridge, and the left ventricular outflow tract is narrowed. After the ultrasound contrast agent was injected into the peripheral vein, the left ventricular systolic pressure was higher than that of the right ventricle, and the diastolic right ventricular pressure was slightly higher than that of the left ventricle. The contrast agent was seen to flow back and forth in the upper part of the ventricular septal defect.

(4) Right heart catheterization: The catheter can enter the left atrium from the right atrium or directly into the left ventricle from the right atrium. There is a left-to-right shunt in the atrial and ventricular levels. The blood oxygen content in the right atrium is higher than that in the vena cava, and the blood oxygen content in the right ventricle may be further increased than in the right atrium. Patients with pulmonary hypertension can show right to left shunt and increased pulmonary vascular resistance. And the right atrial pressure waveform of the mitral valvular fracture can show the increase of V wave caused by atrioventricular valve insufficiency.

(5) Selective left ventriculography can show that the contrast agent flows into the right ventricle and/or the right atrium through the atrial and ventricular septal defect; it flows back into the left and right atrium through the atrioventricular valve nucleus. It can also show the size of the heart septal defect and the atrioventricular valve malformation. In some cases of common room, the contrast agent injected into the left ventricle first flows back into the left atrium, and then enters the right atrium, right ventricle and pulmonary artery sequentially; the complete type of atrioventricular co-channel case contrast agent left ventricular return to the left and right atrium At the same time, the left ventricle directly enters the right ventricle through the ventricular septal defect, and even the left, right atrium and right ventricle, the pulmonary artery is simultaneously developed. In the atrioventricular co-channel case, the position of the atrioventricular valve flap moved to the apex and ventricular septal defect, and the left ventricular outflow tract was narrow and long. The gooseneck sign appeared on the left ventricular angiography. Therefore, selective left ventricular angiography can identify both the first and second atrial septal defects, and is also valuable for the identification of partial and complete atrioventricular common tract.

(6) Atrioventricular tube malformation with complete ventricular septum and no pulmonary hypertension, such as decreased arterial blood oxygen saturation, should be considered as a single atrial malformation.

Differential diagnosis

Diagnosis of atrioventricular tube malformations should be identified in the following diseases:

(a) secondary atrial septal defect

The following points can be identified:

1 Secondary atrial septal defect in the pulmonary valve area and systolic murmur, without murmur of mitral and tricuspid regurgitation.

2 secondary hole type atrial septal defect ECG axis right deviation, incomplete right bundle branch block, right atrium, right ventricle increased. The atrioventricular tube malformation has a left-biased electrical axis and a left anterior bundle branch block.

3 echocardiography and cardiovascular angiography can show ventricular septal defect, crisscross split, atrioventricular valve malformation.

(two) ventricular septal defect

Complete atrioventricular tube malformations have different sizes of ventricular septal defect, similar to large ventricular septal defect, but the latter apical region does not hear systolic murmurs of mitral regurgitation. Differential diagnosis depends on echocardiography and cardiovascular imaging.

(C) simple pulmonary stenosis

Simple pulmonary artery stenosis and complete atrioventricular tube malformation can detect jet murmur in the second intercostal space of the left sternal border, but the former has mild clinical symptoms, the second sound of pulmonary valve is weakened or disappeared, and there is no mitral and tricuspid valve. Closed incomplete murmur, X-ray chest radiograph showed pulmonary less blood, echocardiography can be identified.

(4) Other congenital heart diseases

Such as clinical appearance of purpura, may be misdiagnosed as tetralogy of Fallot, transposition of the great arteries, tricuspid atresia, venous venous drainage, etc., but echocardiography, cardiac catheterization and cardiovascular angiography can be identified.

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