Open atrioventricular canal: symptoms, diagnosis, treatment

The open atrioventricular canal accounts for about 4% of all congenital heart defects. The defect is characterized by underdevelopment of the septa adjacent to the AV valves and anomalies of the valves themselves.

Incomplete (partial) form of patent atrioventricular canal

A primary interatrial defect of varying size is characteristic. The AV valves are formed at the same level (normally the tricuspid valve is shifted to the apex of the heart) and are attached to the upper edge of the interventricular septum. The cleft of the mitral valve leaflet can be in the form of a small marginal diastasis or reach its base. Additional chords often extend from the edges of the cleft and are attached to the interventricular septum: papillary muscle anomalies are possible. Hemodynamic disorders are characterized by regurgitation on the mitral valve and shunting of blood through the atrial septal defect. There is a volume overload of both ventricles, pulmonary hypertension develops (up to the sclerotic phase already in the first years of life). With pulmonary artery stenosis, the course of the defect is more favorable, since pulmonary hypertension does not develop.

Complaints of delayed physical development, repeated pneumonia, loss of appetite, rapid fatigue during feeding, signs of heart failure in the form of tachypnea and tachycardia are typical. Congestive wheezing in the lungs appears, the liver enlarges. The time of appearance of the first signs and the severity of the condition are determined by the severity of mitral insufficiency. With significant regurgitation, the condition of newborns from the first days is severe, since the increase in pressure in the left atrium and the volume of blood discharge are significant.

Physical examination reveals a left-sided cardiac hump, systolic thrill in the fourth intercostal space and/or above the apex of the heart. Auscultation reveals two murmurs with an incomplete form of open AV canal: systolic murmur of mitral regurgitation at the apex of the heart and systolic murmur of relative pulmonary artery stenosis - atrial septal defect (ejection murmur).

ECG is very helpful in diagnostics. Most patients have a leftward deviation of the electrical axis of the heart from 0 to 150 s. The consequence of abnormal formation of the cardiac conduction system is a posterior displacement of the AV node and the bundle of His, early departure of the left bundle branch of the bundle of His or its hypoplasia. As a sign of volume overload of the right ventricle, an incomplete block of the right bundle branch of the bundle of His of the rSR form occurs in lead V1.

The shape and size of the cardiac shadow on the radiograph are determined by the severity of mitral valve insufficiency, in connection with which the shape of the heart resembles that in myocardial diseases (enlarged mainly due to the left sections).

In the case of an incomplete open AV canal, echocardiography reveals signs of a primary atrial septal defect (a break in the echo signal from the interatrial septum) and mitral valve anomalies.

Cardiac catheterization and angiocardiography are performed to determine the extent of damage to the pulmonary vessels in pulmonary hypertension.

Treatment. Drug treatment is aimed at stopping the signs of heart failure. The defect can only be eliminated surgically. Planned intervention is indicated at the age of 1-2 years, and in case of severe mitral insufficiency or common atrium - earlier. Plastic surgery of the defect and reconstruction of the split valve leaflet are performed.

Complete form of atrioventricular canal open atrioventricular canal

The defect includes a primary atrial septal defect, a ventricular septal defect just below the AV valves, and a common AV ring. Blood is shunted at the level of the interatrial and interventricular septum, and AV valve insufficiency develops. There is a volume overload of the left and right chambers of the heart. The pressure in the ventricles equalizes, which leads to the early development of high pulmonary hypertension by the end of the first year of life. In the presence of pulmonary stenosis, the left-to-right shunt decreases.

The defect is characterized by a severe course immediately after the birth of the child. Significant deterioration occurs by the end of the first month, when the resistance of the pulmonary vessels decreases and pulmonary blood flow increases. During this period, the severity of the symptoms of heart failure increases. Children lag behind in development, and repeated pneumonia is not uncommon.

During physical examination of the cardiovascular system, systolic thrill is detected by palpation. A rough systolic murmur along the left edge of the sternum (ventricular septal defect), systolic murmur of valvular insufficiency and an accentuation of the second sound over the pulmonary artery are heard.

ECG changes are similar to those seen with incomplete open AV canal.

On the radiograph, the pulmonary pattern is significantly enhanced along the arterial bed. The heart shadow is usually enlarged due to all chambers. With concomitant pulmonary artery stenosis, the pulmonary pattern is normal, and the heart size is small.

EchoCG allows obtaining a complete morphological and hemodynamic characteristic of the defect. The following information is important for surgical treatment: the size of the defects and valve openings, the anatomy of the valves and the condition of the papillary muscles, the relative and absolute sizes of the ventricles.

Cardiac catheterization and angiocardiography have lost their significance in the diagnosis of open atrioventricular canal. The methods are used to determine the state of the pulmonary vascular bed in cases of high pulmonary hypertension.

Treatment. Drug treatment is aimed at relieving the symptoms of heart failure. Since the complete form of the AV canal is rapidly accompanied by high pulmonary hypertension with sclerotic changes in the vessels, primary radical correction of the defect is indicated - closure of the interatrial and interventricular defects with patches and plastic surgery of the AV valves.

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