Atrial septal defect: symptoms, diagnosis, treatment

Atrial septal defect is one or more openings in the interatrial septum, through which blood is discharged from left to right, pulmonary hypertension and heart failure develop. Symptoms and signs include intolerance to physical exertion, dyspnea, weakness and atrial rhythm disturbances. Often, soft systolic murmurs are heard in the II-III intercostal space to the left of the sternum. The diagnosis is based on echocardiography. Treatment of the defect of the interatrial septum is surgical or through the catheter closure of the defect. Prophylaxis of endocarditis, as a rule, is not required.

Atrial septal defect (ASD) is approximately 6-10% in the structure of congenital heart defects. Most cases are isolated and sporadic, but some are part of the genetic syndrome (eg, mutations of the 5th chromosome, Holt-Oram syndrome).

An atrial septal defect can be classified by location: a secondary defect of the septum [defect in the oval window in the central (or middle) part of the interatrial septum], venous sinus defect (defect in the posterior part of the septum, near the mouth of the superior or inferior vena cava), or primary defect [defect in the anterior-lower part of the septum, is the form of an endocardial shaft defect (atrioventricular communication)].

[1], [2], [3]

What happens if an atrial septal defect is present?

Atrial septal defect is a defect characterized by the presence of a communication between the atria, through which the blood is discharged from left to right and, in contrast to the interventricular defect, under a much smaller pressure gradient. The pressure in the left atrium exceeds that in the right by 8-10 mm Hg. Atrial septal defect is 2-3 times more common in women than in men. Depending on the anatomical localization, the defects of the atrial septum are divided into primary (in the lower part of the interatrial septum above the AV apertures) and secondary (more often central, so-called defects of the oval fossa). Up to 66%. As a result of the discharge of blood, the overload of the right divisions increases, gradually (slower than with an interventricular septal defect), heart failure progresses. Several factors contribute to the prolonged absence of pulmonary hypertension in the presence of an atrial septal defect: there is no direct effect on the vessels of the lungs of high left ventricular pressure (in the case of an interventricular septal defect and an open arterial duct, the latter is directly transmitted to the vessels of the small circle of circulation), the right heart is dilated, vessels of the small circle of blood circulation and their low resistance.

To understand hemodynamic changes in the defect of the interatrial septum (and other vices), one should understand the intracardiac hemodynamics in the norm. At defect of the interatrial septum, first left-handed discharge of blood occurs. Most of the small defects of the interatrial septum are spontaneously closed during the first years of life. Nevertheless, with large defects, the right atrium and ventricular volume are overloaded, the pressure in the pulmonary artery, pulmonary vascular resistance increases, and the right ventricular hypertrophy develops. Later, atrial fibrillation may develop. Ultimately, increased pressure in the right heart can lead to a bi-directional discharge of blood and the appearance of cyanosis (see "Eisenmenger syndrome").

Symptoms of atrial septal defect

In most cases, a small defect of the interatrial septum is asymptomatic. Most children with a defect of the interatrial septum lead a normal life, some even go in for sports. Gradually, with age, there is a greater fatigue, dyspnoea with physical exertion. Cyanosis does not happen. If the size of the defect is large, intolerance of physical exertion, dyspnoea with tension, weakness and atrial rhythm disturbances, and sometimes a palpitation may be noted. The passage of microemboli from the veins of the great circle of blood through the defect of the interatrial septum (paradoxical embolization), often combined with arrhythmias, can lead to thromboembolism of the vessels of the brain or other organs. Rarely, if the defect of the interatrial septum is not diagnosed on time, Eisenmenger syndrome develops.

In the anamnesis in patients with a defect of the interatrial septum, repeated bronchitis, and occasionally pneumonia. Often the children of the first months and years of life are marked by a severe course of blemish with shortness of breath, tachycardia, lag in physical development, hepatomegaly. After 2-3 years, well-being can improve, signs of heart failure disappear.

When auscultation in children in II-III intercostal space, systolic murmur (or ejection noise) is usually heard on the left, the intensity gradation is 2-3 / 6, the splitting of II tone over the pulmonary artery (top left along the edge of the sternum). With a significant discharge of blood from left to right, diastolic low-pitched sounds can be heard (by increasing the blood flow on the tricuspid valve) along the edge of the sternum at the bottom left. These auscultative data may not be present in infants, even if there is a large defect. There may be a distinct epigastric pulsation (right ventricle).

Diagnosis of atrial septal defect

The diagnosis is based on the findings of a physical examination of the heart, radiography of the chest and ECG, confirmed by echocardiography using color Dopplercardiography.

Cardiac catheterization is usually not required unless one suspects the presence of a combination of heart defects.

At a clinical examination, the hump is detected at an older age in children with cardiomegaly, systolic jitter is rarely detected, its presence indicates the possibility of concomitant malformation (pulmonary artery stenosis, interventricular septal defect). The apical impulse is weakened, unshrouded. The boundaries of relative cardiac dullness can be widened in both directions, but at the expense of the right divisions: the left border - due to the leftward displacement of the enlarged right ventricle of the left one, the right border - at the expense of the right atrium.

The main auscultative sign, which allows one to suspect a defect of the interatrial septum, is a systolic murmur of medium intensity, non-rough, without pronounced conductivity, with localization in the second to third intercostal space to the left of the sternum, better audible in orthostasis. The opinion about the origin of systolic noise is one: it is associated with functional stenosis of the pulmonary artery, arising from the increase in blood flow with the unchanged fibrous ring of the pulmonary valve. As the pressure in the pulmonary artery increases, an accent of the second tone appears over the pulmonary artery.

With the development of a relative deficiency of the tricuspid valve, atrial overload increases, and cardiac rhythm disturbances may occur. The ECG is characterized by a deviation of the electric axis of the heart to the right up to +90 ... + 120. The signs of right ventricular congestion are of a nonspecific character: the incomplete blockade of the right leg of the Guus start in the form of rSR in lead V1. As the pressure in the pulmonary artery increases and the right ventricle overloads, the amplitude of the R wave increases. There are also signs of an overload of the right atrium.

This defect has no specific radiographic signs. There is an increase in pulmonary pattern. The change in the size of the heart on the roentgenogram is determined by the size of the discharge. In oblique projections it is clear that the heart is enlarged due to the right chambers. When chest radiographs are detected, cardiomegaly with dilatation of the right atrium and right ventricle, expansion of the shadow of the pulmonary artery and intensification of the pulmonary pattern.

Transthoracic two-dimensional echocardiography allows to directly detect an echo break in the zone of the interatrial septum. The diameter of the atrial septal defect, determined echocardiographically, almost always differs from that measured during surgery, which is due to the stretching of the heart by moving blood (during the operation the heart is relaxed and emptied). That is why the measurement of fixed tissue structures can be made quite accurately, and the changing parameters (hole or cavity diameter) are always with a certain error.

Cardiac catheterization and angiocardiography have now lost their significance in the diagnosis of an atrial septal defect. The use of these methods is advisable only if it is necessary to accurately measure the discharge through a defect or the degree of pulmonary hypertension (in patients of older age groups), and also the length of the diagnosis of concomitant pathology (eg abnormal drainage of pulmonary veins).

[4], [5], [6], [7], [8]

Differential diagnosis of atrial septal defect

Differential diagnosis in the secondary defect of the interatrial septum is primarily performed with functional systolic murmur, which is heard on the basis of the heart. The latter weakens in a standing position, the right parts of the heart are not enlarged, the incomplete blockade of the right leg of the bundle is not characteristic of the head. Quite often the atrial septal defect has to be differentiated from such diseases as isolated pulmonary artery stenosis, Fallot triad, abnormal drainage of pulmonary veins, interventricular septal defect, anomaly of the development of the tricuspid valve (Ebstein's anomaly).

[9], [10], [11], [12], [13], [14]

Treatment of atrial septal defect

Most of the small defects (less than 3 mm) are closed spontaneously; approximately 80% of defects with a diameter of 3-8 mm close spontaneously to 18 months. At the same time, there is no spontaneous closure of primary atrial septal defects and venous sinus defects.

If there is a small defect without clinical manifestations, the child is observed with an annual echocardiography. Since these children are at risk of paradoxical embolism, some centers recommend using closure of the defect with the help of catheterization (for example, Amplatzer Septal Occluder, Cardioseal device), even with a small defect size. However, these devices do not apply if the atrial septal defect is primary or venous sinus defects, since these defects are located next to important structures.

In the presence of heart failure, therapy is aimed at reducing hypervolemia of the small circle of circulation and increasing the antegrade flow through the left heart. Assign diuretics and cardiac glycosides. The operation is indicated with increasing heart failure, lagging behind in physical development, repeated pneumonia. Hemodynamic indication for surgery - the ratio of pulmonary and systemic blood flow 2: 1, which is possible even with minor clinical symptoms. On this basis, the defect of the interatrial septum can be called an "insidious" defect. Traditional surgical correction lies in suturing the defect or its plastic through thoracotomy access in conditions of artificial circulation. In the last decade, endovascular methods of closing defects are intensively developing with the help of special devices - occluders. The procedure is performed by puncturing peripheral vessels, followed by the delivery of a special "umbrella" or "button device" to the defect. To perform this procedure, there are a number of anatomical limitations: endovascular intervention is possible only in the case of a secondary defect of the atrial septum up to 25-40 mm in size, located far enough from the coronary sinus, AV valves, pulmonary and hollow veins.

Patients with medium and large defects (the ratio of pulmonary blood flow to the systemic blood flow more than 1.5: 1) shows the closure of the defect, usually between the ages of 2 and 6 years. It is preferable to use the closure of the defect during catheterization if there are adequate anatomical characteristics and a defect diameter of less than 13 mm. In other cases, surgical closure of the defect is indicated. When the defect is closed in childhood, perioperative lethality reaches zero, and the life span is the mean value in the population. Before the closure of the defect, patients with large defects and heart failure are prescribed diuretics, digoxin and ACE inhibitors. 

If the patient has a primary atrial septal defect, endocarditis prophylaxis should be performed; prevention of endocarditis is not indicated in secondary defects and defects in the venous sinus.