Atrial Septal Defect: When Does the Size Become Critical?

An atrial septal defect (ASD) measuring 10mm after birth is generally considered significant. While some defects may grow as the child gains weight and develops, the severity largely depends on the size and type of the defect. The most common form of ASD is the secundum type, which accounts for a large percentage of congenital heart diseases. Most cases involve a single hole, although some may have multiple openings. In rare cases, a complete absence of the atrial septum results in a condition known as common atrium.

Symptoms and Detection

In many cases, children with smaller ASDs may not exhibit noticeable symptoms. The heart murmur associated with such defects is often soft and may be overlooked during routine exams. Frequently, children are brought in for medical attention due to recurring respiratory infections. Most diagnoses occur during preschool or early school years when a heart murmur is detected during a general health screening.

Diagnosis and Monitoring

Thanks to advances in medical imaging, echocardiography has become the gold standard for diagnosing ASD. It allows doctors to determine both the presence and size of the defect. For defects smaller than 5mm, physicians often recommend regular follow-ups, as these may close naturally after the first year of life, especially if related to patent foramen ovale. However, if the foramen ovale remains open beyond the age of two or three, a percutaneous closure using a catheter-delivered device may be considered after the age of three.

Management Based on Defect Size

Moderate-Sized Defects (5–8mm)

Defects in the range of 5 to 8mm require careful monitoring. The chance of spontaneous closure diminishes with size, so regular cardiology check-ups are essential to assess the impact on heart function and growth.

Large Defects (>10mm)

Children with defects larger than 10mm are typically advised to undergo surgical repair. This is crucial to prevent complications such as shortness of breath, reduced exercise tolerance, delayed growth and development, and frequent lung infections. If left untreated, a large ASD can lead to serious consequences including impaired heart development and heart failure.