Atrial septal defect: what is it, symptoms, causes, treatment, prognosis

General information about the disease

Atrial septal defect (ASD) is a rare congenital heart disease characterized by an opening in the wall (septum) that separates the two upper chambers (atria) of the heart.

The heart usually has four chambers: two upper chambers, known as the atria, separated from each other by a fibrous septum known as the atrial septum, and two lower chambers, known as the ventricles, separated from each other by the ventricular septum.

The valves connect the atria (left and right) to the corresponding ventricles. At birth, there is a small opening (foramen ovale) between the two atria. Soon after birth, the atrial septum gradually grows and closes this opening. In children with ASD, the atrial septum may not close properly or become damaged during fetal development. In this disorder (called an open foramen ovale), the opening between the atria remains for a long time, although it must be closed, resulting in increased workload on the right side of the heart and excessive blood flow to easy.

Initially, symptoms associated with an atrial septal defect may be absent or so mild that they may go unnoticed. Often, the disorder is not recognized until school age or even adulthood. Adults with an undetected atrial septal defect may develop a variety of breathing problems and / or heart failure.

Several forms of ASD have been identified. They are classified according to their location in the partition. The primary form (type ostium primum) refers to a defect located in the lower part of the septum. The secondary form (type ostium secundum) refers to a defect located in the middle of the septum, and the sinus venosus form (defect of the venous sinus) refers to defects in the upper part of the septum.

Signs and symptoms

Secondary form of ASD is the most common form of this group of heart defects. The middle part of the interatrial septum in the foramen ovale does not close during fetal development. The size of the hole can vary, along with the severity of the symptoms.

Primary ASD is less common. The lower part of the interatrial septum cannot develop normally, leaving an opening between the atria. Often the valves that separate the atria from their respective ventricles (tricuspid and mitral) are also deformed, and the septum that separates the ventricles may also be defective or deformed (atrioventricular defect partitions). Another defect (endocardial cushion defect) possibly occurs during embryonic development in the tissue that forms the septum, dividing the heart into atria and ventricles.

Venous sinus defect, the least common form of ASD, occurs when there is an opening in the top of the atrial septum. This defect is often associated with malformations of a vein that leads from the lungs to the heart (right pulmonary vein). One of the main veins in the body that returns blood to the heart (superior vena cava) can also be damaged.

Most children with atrial septal defects have no symptoms. Several affected children may be abnormally thin and experience mild growth retardation and an increased susceptibility to respiratory infections. Other very severely impaired children, especially those with the primary form of the defect, may experience shortness of breath, easy exercise fatigue and / or an irregular heartbeat (arrhythmias).

Murmur in the heart is the most common sign and usually the only sign of ASD in children. There may also be changes in heart tone that represent closure of heart valves.

At around age 40, people with ASD may experience symptoms associated with increased pressure in the blood vessels of the lungs (pulmonary hypertension). The increased pressure in these vessels causes blood to move or "shunt" through an abnormal opening in the heart. Symptoms may include bluish discoloration of the skin (cyanosis), cracked fingertips, exercise intolerance and / or an abnormal increase in the number of circulating red blood cells (polycythemia). Can also develop abscesses in the brain. Other symptoms may include edema arms and legs and / or shortness of breath.

Severe cases of ASD can lead to life-threatening complications such as chest pain, irregular heartbeat (arrhythmia), abnormal enlargement of the heart, "flutter" of the heart (atrial fibrillation) and / or heart failure. Women with atrial septal defects who become pregnant may be at risk for blood clots. These clots (blood clots) can separate from the walls of blood vessels and travel through the systemic circulation, causing embolism.

Causes

Most cases of atrial septal defects occur spontaneously for no apparent reason (sporadically). The exact nature of the developmental defect or defects that may arise during embryonic development (embryogenesis) remains unclear.

Some cases of ASD occur in families. In such rare cases, two types, ostium primum and ostium secundum, appear to be inherited as autosomal dominant genetic traits. To further complicate matters, genetic analysis suggests that there are at least two various genetic disorders associated with ASD, which are associated with mutations in a gene called Nkx2-5.

Chromosomes, which are present in the nucleus of human cells, carry genetic information for each person. The cells of the human body usually have 46 chromosomes. Pairs of human chromosomes are numbered 1 through 22, and the sex chromosomes are labeled X and Y. Men have one X and one Y chromosome, while women have two X chromosomes. Each chromosome has a short arm, labeled "p", and a long arm, labeled "q". Chromosomes are further subdivided into many numbered bands. For example, “chromosome 6p21.3” refers to band 21.3 on the short arm of chromosome 6. Likewise, "chromosome 8p23.1-p22" refers to the region between bands 22 and 23.1 on the short arm of chromosome 8. The numbered stripes indicate the location of the thousands of genes that are present on each chromosome.

Genetic diseases are defined by a combination of genes for a specific trait, which are found on chromosomes received from the father and mother.

Dominant genetic disorders occur when only one copy of an abnormal gene is needed for a disease to appear. The abnormal gene can be inherited from either parent, or it can be the result of a new mutation (gene change) in the affected person. The risk of passing the abnormal gene from the affected parent to the offspring is 50% for each pregnancy, regardless of the sex of the child.

Recessive genetic disorders occur when a person inherits the same abnormal gene for one trait from each parent. If a person receives one normal gene and one gene for the disease, the person will be a carrier of the disease, but usually asymptomatic. The risk that two carrier parents will both pass on the defective gene and therefore have a sick child is 25 percent in every pregnancy. The risk of having a child who will be a carrier, like a parent, is 50 percent with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for this particular disease is 25 percent. The risk is the same for men and women.

All humans carry 4-5 abnormal genes. Parents who are close relatives (brother and sister) have a higher chance than unrelated parents who have the same abnormal gene, which increases the risk of having children with recessive genetic disorder.

Atrial septal defect can also occur in connection with many other congenital heart defects, or in newborns that are relatively small or premature. The primary form of the disease is common in people with Down syndrome or Ellis van Creveld syndrome.

Affected populations

Atrial septal defect is a rare congenital heart disease that affects more women than men (2 or 3: 1). About 1 percent of all babies are born with a congenital heart defect. About 10 percent of these children have atrial septal defects.

Although atrial septal defects can be diagnosed in infancy or in children with the age of 6 months to 3 years, the disorder is usually diagnosed after 40 years of age, when it often appears symptoms. Symptoms can be seen at an earlier age if the defects are very serious or if the affected people live at high altitudes (eg in the mountains). This is due to a slight narrowing of the arteries of the heart and lungs at high altitudes.

The primary form (type ostium primum) can occur in people with Down syndrome or in more than 50 percent of people with Ellis van Creveld syndrome. These defects can also occur in connection with a number of other disorders.

Symptomatic disorders

Symptoms of the following disorders may be similar to those of atrial septal defects. Comparisons can be useful for differential diagnosis:

• Atrioventricular (AV) septal defect - a rare heart disease that is present at birth (congenital) and is characterized by abnormal development of the septa and heart valves. Children with the complete defect usually develop congestive heart failure. Often, excess fluid builds up in certain areas of the body, especially the lungs. This pulmonary congestion can lead to difficulty breathing (shortness of breath). Other symptoms may include bluish discoloration of the skin (cyanosis), poor diet, abnormally fast breathing (tachypnea) and heart rate (tachycardia) and / or excessive sweating (hyperhidrosis). Adults with an AV septal defect may experience abnormally low blood pressure, irregular heartbeats, and / or rapid heartbeat.
• Ventricular septal defect(DMZHP) are a group of common congenital heart defects characterized by the absence of one ventricle. Children with these defects may have 2 atria and 1 large ventricle. Symptoms of these conditions are similar to an atrioventricular septal defect and may include abnormal rapid breathing rate (tachypnea), wheezing, heart palpitations (tachycardia), and / or abnormally increased liver (hepatomegaly). A ventricular septal defect can also cause excessive accumulation of fluid around the heart, leading to congestive heart failure.
• Three atrial heart - extremely rare congenital heart disease, characterized by the presence of an additional chamber above the left atrium of the heart. The pulmonary veins that return blood from the lungs drain into this additional “third chamber”. Symptoms of a tricyclic heart vary greatly and depend on the size of the opening between the chambers. Symptoms may include abnormally fast breathing (tachypnea), wheezing, coughing, and / or abnormal buildup fluid in the lungs (pulmonary hyperemia).
• The only ventricle of the heart - extremely rare congenital heart disease, characterized by the absence of one ventricle. Children with this defect have two atria and one large ventricle. Symptoms are similar to those of an atrial septal defect and include shortness of breath (shortness of breath), excessive fluid accumulation in and around the lungs (pulmonary edema) and / or bluish discoloration of the skin and mucous membranes (cyanosis). Other symptoms may include poor eating habits, abnormally rapid breathing (tachypnea), and / or an abnormally rapid heart rate (tachycardia).
• Mitral valve stenosis Is a rare heart disease that may be present at birth or be acquired acquired. It is characterized by abnormal narrowing of the mitral valve opening. In the congenital form, symptoms vary greatly and may include coughing, shortness of breath, heart palpitations, and / or frequent respiratory infections. With acquired mitral stenosis, symptoms may also include weakness, abdominal discomfort, chest pain (angina) and / or periodic loss of consciousness.

Atrial septal defect can occur in connection with a variety of other disorders, including:

• Down syndrome;
• Ellis van Creveld's syndrome;
• Smith-Lemli-Opitz syndrome;
• Costello syndrome;
• chondroectodermal dysplasia;
• rubella fetus;
• Holt-Oram syndrome;
• Hurler's syndrome and others.

Diagnostics

The diagnosis of atrial septal defects is confirmed by a thorough clinical examination and special tests that allow doctors to assess the structure and function of the heart. These tests may include x-rays, electrocardiogram (ECG), echocardiogram, and cardiac catheterization.

X-rays can reveal abnormal enlargement of the heart or a malformation of other structures in the heart. During an echocardiogram, ultrasound waves are sent to the heart, allowing doctors to study the movement and function of the heart. During cardiac catheterization, a small, hollow tube (catheter) is inserted into a large vein and pierces the blood vessels that lead to the heart. This procedure allows doctors to determine the rate of blood flow through the heart, measure the pressure in the heart, and / or carefully identify anatomical abnormalities.

Standard treatments

Treatment is usually surgical with drugs limited to the period during which the patient is awaiting surgery. In the case of the smallest patients, “watchful waiting” is often sufficient, as the opening is closed as the child grows.

- Surgical intervention.

Until recently, surgery to close the opening of the heart was the preferred form of treatment. Open heart surgery was designed to suture the edges of the hole and close it. In some cases, the hole can be patched and closed with a graft or prosthesis. The success rate is high for these surgical procedures. In the primary form of ASD, surgery can be performed to repair or replace the atrioventricular valves. The success rate for this complex procedure is much lower. The operation is optimally performed between the ages of 3 and 6 years.

In recent years, a less traumatic method of closing the septum opening has been developed using catheters, to which a special device is attached, designed to close the opening partitions. During this procedure, a long, thin tube (catheter) is inserted into a large vein in the baby's upper leg and gently pushed through the blood vessel until it reaches the heart. When the catheter reaches the desired point, a device for closing the defect is fed through its tip, which opens and seals the opening hermetically.

Forecast

Although life expectancy is not normal for patients with ASD, patients tend to survive into adulthood without surgery or percutaneous intervention, and many patients live to old age. However, natural survival after age 40-50 is less than 50%, and the wasting rate after 40 years is about 6% per year. Prolonged pulmonary hypertension rarely occurs before the third decade. Late complications are stroke and atrial fibrillation.