fbpx

Atrial septal defect

Updated : May 17, 2024





Background

Atrial septal defect is among the most prevalent congenital heart defects, affecting approximately 25% of children with heart conditions. This condition arises due to a failure in closing the natural opening between the right and left atria during development. It encompasses a range of defects, including those involving the actual septal membrane and other openings that enable communication between the atria.

There are five primary types of atrial septal defects, listed from most common to least: patent foramen ovale, ostium primum defect, ostium secundum defect, coronary sinus defect, and sinus venosus defect. In many cases, small atrial septal defects tend to close spontaneously during childhood. However, larger defects that do not close on their own may necessitate either a percutaneous procedure or surgical intervention to prevent potential complications such as irregular heart rhythms, pulmonary hypertension, and stroke.

Epidemiology

Atrial septal defect is one of the most common congenital heart defects. The exact incidence and prevalence can vary by region and population. In general, it occurs in approximately 1 in every 1,500 live births. Some studies have shown a gender difference in the prevalence of ASD. It is more commonly diagnosed in females than in males.

However, the extent of this difference can vary among different types of atrial septal defects. It is typically diagnosed in childhood, but it can sometimes go undetected until adulthood, especially in cases of small or asymptomatic defects. There is evidence to suggest that family history and genetics can play a role in the development of ASD. Individuals with a family history of congenital heart defects may be at a higher risk.

Anatomy

Pathophysiology

pregnancy. It involves the development of the primary atrial septum, which starts to grow from the roof of the primitive atrium toward the endocardial cushions. The caudal end of this septum is covered by mesenchymal cells originating from the embryonic endocardium. When the leading edge of the septum primum attaches to the atrioventricular cushions in the front, it effectively divides the primitive atrium into the right and left atria.

During fetal development, the foramen ovale serves a crucial function by allowing oxygen-rich blood to bypass the lungs. This occurs as blood flows directly from the right atrium to the left atrium. However, upon birth and the initiation of breathing, changes in pulmonary vascular resistance lead to a decrease in right atrial pressure, facilitating the closure of the septum primum and thus closing the foramen ovale.

Under normal conditions, the pressure in the right atrium is notably lower than in the left atrium, resulting in a left-to-right shunt where blood flows from the left to the right atrium. As pulmonary pressures eventually equal systemic pressures, this shunt across the atrial septal defect reverses, causing deoxygenated blood to flow into the left atrium and subsequently into the systemic circulation.

However, in cases where the reversal of the shunt across an atrial septal defect is prompted by pulmonary hypertension, a condition known as Eisenmenger syndrome can develop. This syndrome arises when elevated pulmonary pressures lead to a reversal of the shunt, causing deoxygenated blood to flow from the right to the left atrium and into the systemic circulation, resulting in significant health complications.

Etiology

Genetic Factors:

Genetic factors can play a role in the development of atrial septal defect. Some cases appear to have a familial component, suggesting a genetic predisposition. Mutations in certain genes may increase the risk of a child being born with an ASD, although the genetic basis is complex and not fully understood.

Environmental Factors:

Maternal exposure to certain environmental factors during pregnancy may increase the risk of ASD in the developing fetus. These factors can include maternal smoking, alcohol consumption, certain medications, rubella infection, and exposure to toxins.

Hemodynamic Factors:

In some cases, hemodynamic factors may contribute to the development of ASD. Hemodynamics refers to the flow of blood within the heart and blood vessels. Abnormal blood flow patterns during fetal development could potentially lead to the formation of an ASD.

Genetics

Prognostic Factors

Clinical History

Atrial septal defect is typically diagnosed in childhood, but it can sometimes go undetected until adulthood, especially if the defect is small and asymptomatic. A clinical history often involves identifying risk factors during prenatal or postnatal assessments. A family history of congenital heart defects or genetic syndromes can be relevant. In some cases, individuals with small defects may have no noticeable symptoms. However, larger defects or those causing significant shunting of blood can lead to various signs and symptoms, which may include:

  • Fatigue
  • Shortness of breath, especially during physical activity
  • Frequent respiratory infections
  • Difficulty gaining weight (especially in infants and children)
  • Arrhythmias

The duration of the condition depends on whether the atrial septal defect is detected and treated. Small atrial septal defects may close spontaneously during childhood, while larger ones may persist into adulthood. If left untreated, ASD can lead to complications over time.

Physical Examination

A common physical finding in atrial septal defect is the presence of a heart murmur. This is a whooshing or blowing sound that can be heard. The murmur is typically heard during auscultation of the heart, and it is caused by the turbulent blood flow through the atrial septal defect. The murmur may be described as a systolic ejection murmur or a continuous murmur, depending on the size and location of the defect. In addition to the heart murmur, other abnormal heart sounds may be present.

These sounds could be indicative of arrhythmias or other heart conditions that can be associated with ASD. In such cases, physical findings may include a prominent pulmonic component of the second heart sound which is louder than the aortic component. An elevated jugular venous pressure, hepatomegaly, and peripheral edema may also be observed. In cases of a large ASD with significant right-to-left shunting of blood, cyanosis may be evident, particularly in infants.

Age group

Associated comorbidity

Associated activity

Acuity of presentation

Differential Diagnoses

Atrioventricular septal defect

Ventricular septal defect

Pulmonary stenosis

Truncus arteriosus

Tricuspid atresia

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

Indications for Intervention:

Symptomatic Patients: Individuals who experience symptoms such as fatigue, shortness of breath, or arrhythmias are often candidates for intervention, regardless of the defect’s size.

Large or Hemodynamically Significant ASDs: Large defects causing significant shunting of blood may require closure to prevent long-term complications, such as pulmonary hypertension.

Pulmonary Hypertension: If atrial septal defects lead to significant pulmonary hypertension, intervention is often indicated to avoid the development of Eisenmenger syndrome.

Timing of Intervention:

The timing of intervention is based on clinical evaluation and diagnostic tests. For children, intervention may be recommended during early childhood to prevent symptoms and long-term complications. In adults, the timing depends on the severity of symptoms, the presence of complications, and the size of the defect.

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

Intervention with a procedure

  • Transcatheter Closure: This is a minimally invasive procedure performed in a catheterization lab. A thin, flexible tube (catheter) is inserted through a blood vessel in the groin and guided to the heart. An occluder device (e.g., Amplatzer septal occluder) is then placed to block the defect. This is a common approach for secundum ASDs. 
  • Surgical Closure: In some cases, open-heart surgery is necessary, especially for complex ASDs or when transcatheter closure is not feasible. The surgeon makes an incision in the chest, accesses the heart, and sutures or patches the hole in the atrial septum. Surgical closure may be recommended for certain ASD types, such as primum or sinus venosus defects. 

Medication

Media Gallary

References

Atrial septal defect

Updated : May 17, 2024




Atrial septal defect is among the most prevalent congenital heart defects, affecting approximately 25% of children with heart conditions. This condition arises due to a failure in closing the natural opening between the right and left atria during development. It encompasses a range of defects, including those involving the actual septal membrane and other openings that enable communication between the atria.

There are five primary types of atrial septal defects, listed from most common to least: patent foramen ovale, ostium primum defect, ostium secundum defect, coronary sinus defect, and sinus venosus defect. In many cases, small atrial septal defects tend to close spontaneously during childhood. However, larger defects that do not close on their own may necessitate either a percutaneous procedure or surgical intervention to prevent potential complications such as irregular heart rhythms, pulmonary hypertension, and stroke.

Atrial septal defect is one of the most common congenital heart defects. The exact incidence and prevalence can vary by region and population. In general, it occurs in approximately 1 in every 1,500 live births. Some studies have shown a gender difference in the prevalence of ASD. It is more commonly diagnosed in females than in males.

However, the extent of this difference can vary among different types of atrial septal defects. It is typically diagnosed in childhood, but it can sometimes go undetected until adulthood, especially in cases of small or asymptomatic defects. There is evidence to suggest that family history and genetics can play a role in the development of ASD. Individuals with a family history of congenital heart defects may be at a higher risk.

pregnancy. It involves the development of the primary atrial septum, which starts to grow from the roof of the primitive atrium toward the endocardial cushions. The caudal end of this septum is covered by mesenchymal cells originating from the embryonic endocardium. When the leading edge of the septum primum attaches to the atrioventricular cushions in the front, it effectively divides the primitive atrium into the right and left atria.

During fetal development, the foramen ovale serves a crucial function by allowing oxygen-rich blood to bypass the lungs. This occurs as blood flows directly from the right atrium to the left atrium. However, upon birth and the initiation of breathing, changes in pulmonary vascular resistance lead to a decrease in right atrial pressure, facilitating the closure of the septum primum and thus closing the foramen ovale.

Under normal conditions, the pressure in the right atrium is notably lower than in the left atrium, resulting in a left-to-right shunt where blood flows from the left to the right atrium. As pulmonary pressures eventually equal systemic pressures, this shunt across the atrial septal defect reverses, causing deoxygenated blood to flow into the left atrium and subsequently into the systemic circulation.

However, in cases where the reversal of the shunt across an atrial septal defect is prompted by pulmonary hypertension, a condition known as Eisenmenger syndrome can develop. This syndrome arises when elevated pulmonary pressures lead to a reversal of the shunt, causing deoxygenated blood to flow from the right to the left atrium and into the systemic circulation, resulting in significant health complications.

Genetic Factors:

Genetic factors can play a role in the development of atrial septal defect. Some cases appear to have a familial component, suggesting a genetic predisposition. Mutations in certain genes may increase the risk of a child being born with an ASD, although the genetic basis is complex and not fully understood.

Environmental Factors:

Maternal exposure to certain environmental factors during pregnancy may increase the risk of ASD in the developing fetus. These factors can include maternal smoking, alcohol consumption, certain medications, rubella infection, and exposure to toxins.

Hemodynamic Factors:

In some cases, hemodynamic factors may contribute to the development of ASD. Hemodynamics refers to the flow of blood within the heart and blood vessels. Abnormal blood flow patterns during fetal development could potentially lead to the formation of an ASD.

Atrial septal defect is typically diagnosed in childhood, but it can sometimes go undetected until adulthood, especially if the defect is small and asymptomatic. A clinical history often involves identifying risk factors during prenatal or postnatal assessments. A family history of congenital heart defects or genetic syndromes can be relevant. In some cases, individuals with small defects may have no noticeable symptoms. However, larger defects or those causing significant shunting of blood can lead to various signs and symptoms, which may include:

  • Fatigue
  • Shortness of breath, especially during physical activity
  • Frequent respiratory infections
  • Difficulty gaining weight (especially in infants and children)
  • Arrhythmias

The duration of the condition depends on whether the atrial septal defect is detected and treated. Small atrial septal defects may close spontaneously during childhood, while larger ones may persist into adulthood. If left untreated, ASD can lead to complications over time.

A common physical finding in atrial septal defect is the presence of a heart murmur. This is a whooshing or blowing sound that can be heard. The murmur is typically heard during auscultation of the heart, and it is caused by the turbulent blood flow through the atrial septal defect. The murmur may be described as a systolic ejection murmur or a continuous murmur, depending on the size and location of the defect. In addition to the heart murmur, other abnormal heart sounds may be present.

These sounds could be indicative of arrhythmias or other heart conditions that can be associated with ASD. In such cases, physical findings may include a prominent pulmonic component of the second heart sound which is louder than the aortic component. An elevated jugular venous pressure, hepatomegaly, and peripheral edema may also be observed. In cases of a large ASD with significant right-to-left shunting of blood, cyanosis may be evident, particularly in infants.

Atrioventricular septal defect

Ventricular septal defect

Pulmonary stenosis

Truncus arteriosus

Tricuspid atresia

Indications for Intervention:

Symptomatic Patients: Individuals who experience symptoms such as fatigue, shortness of breath, or arrhythmias are often candidates for intervention, regardless of the defect’s size.

Large or Hemodynamically Significant ASDs: Large defects causing significant shunting of blood may require closure to prevent long-term complications, such as pulmonary hypertension.

Pulmonary Hypertension: If atrial septal defects lead to significant pulmonary hypertension, intervention is often indicated to avoid the development of Eisenmenger syndrome.

Timing of Intervention:

The timing of intervention is based on clinical evaluation and diagnostic tests. For children, intervention may be recommended during early childhood to prevent symptoms and long-term complications. In adults, the timing depends on the severity of symptoms, the presence of complications, and the size of the defect.

  • Transcatheter Closure: This is a minimally invasive procedure performed in a catheterization lab. A thin, flexible tube (catheter) is inserted through a blood vessel in the groin and guided to the heart. An occluder device (e.g., Amplatzer septal occluder) is then placed to block the defect. This is a common approach for secundum ASDs. 
  • Surgical Closure: In some cases, open-heart surgery is necessary, especially for complex ASDs or when transcatheter closure is not feasible. The surgeon makes an incision in the chest, accesses the heart, and sutures or patches the hole in the atrial septum. Surgical closure may be recommended for certain ASD types, such as primum or sinus venosus defects.