Atrial Septal Defect and Patent Foramen Ovale Explained

Atrial Septal Defect (ASD) and Patent Foramen Ovale (PFO) are among the more commonly diagnosed congenital heart conditions in children. An ASD typically occurs when there is an abnormal development, absorption, or fusion of the atrial septum during embryonic growth. This results in a persistent opening between the left and right atria of the heart. It is one of the most frequently observed forms of congenital heart disease in children.

Types of Atrial Septal Defects

ASDs can be categorized into different types based on their origin and location. The most common type is the secundum defect, also known as a second-hole defect, which accounts for nearly 80% of all ASD cases. Another type is the primum defect, or first-hole defect, which occurs lower in the septum and is often associated with other heart abnormalities.

Other Forms of Septal Defects

In addition to the common secundum defects, there are other variations such as sinus venosus defects, which occur near the superior vena cava, and inferior vena cava defects. There is also a mixed type with characteristics of multiple defect patterns. A rare and more severe condition is complete atrial septal defect, where the atrial septum is entirely absent, resulting in a single atrial chamber instead of two separate ones.

Understanding Patent Foramen Ovale

The foramen ovale is a natural opening between the atria that exists during fetal development to help blood bypass the lungs. Normally, this opening closes shortly after birth. However, in about 20% to 30% of people, it remains functionally closed but not completely sealed anatomically. This condition is known as Patent Foramen Ovale (PFO) and is generally asymptomatic and often discovered incidentally during routine heart examinations.