Hello and welcome to the Zero to Finals podcast. My name is Tom and in this episode

I'm going to be talking to you about atrial septal defects. And you can find written notes on this topic

at zero tofinals.com slash ASD or in the cardiology section of the Zero to Finals Pediatrics

book. So let's get straight into it.

An atrial septal defect is a defect or a hole in the septum or the wall between the two atria.

This connects the right and the left atria, allowing blood to flow between them.

Let's start with some basic pathophysiology.

During the development of the fetus, the right and the left atria are connected. Two walls

grow downwards from the top of the heart, then fuse together with the endocardial cushion

in the middle of the heart to separate the atria.

These two walls are called the septum primum and the septum secondum.

Defects in these two walls lead to atrial septal defects, which is a hole connecting the left

and the right atria.

It's normal for there to be a small hole in the septum secondum, and this is called the

Pharum Ovali. The forumon ovale normally closes at birth.

An atrial septal defect leads to a shunt, with blood moving between the two atria.

Blood moves from the left atrium to the

right atrium because the pressure in the left atrium is higher than the pressure in the right

atrium. This means blood continues to flow through the pulmonary vessels and the lungs to get

oxygenated and the patient does not become cyanotic. However, the increased flow to the right side of the heart leads to right-sided

overload and right-heart strain.

This right-sided overload can lead to right heart failure and pulmonary hypertension.

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