What is an ASD?
The heart has four chambers. An atrial septal defect is a hole in the wall (the septum) separating the two upper chambers — the left and right atria. Because of the way pressures work in the heart, blood leaks from the left side to the right, meaning the right side of the heart and the lungs handle more blood than they should.
A small ASD may cause no problems at all for years. A larger one, left untreated for long enough, can eventually strain the right side of the heart and the blood vessels in the lungs — which is why finding and sizing it accurately matters, even when a child feels completely well.
Signs that may point to it
How it is diagnosed and treated
An echocardiogram shows the size, position and effect of the hole, and is usually all that is needed to plan treatment. Many small ASDs close on their own in early childhood and simply need periodic review.
Where closure is needed, most ASDs suitable in size and position can be closed with a device carried to the heart through a catheter in the leg vein — no incision in the chest, and typically a one-night hospital stay. Some are treated with day surgery instead, when the position or size makes that the safer route.