ASDs typically allow which type of blood shunt?

Atrial septal defects (ASDs) are congenital heart defects characterized by an abnormal opening in the atrial septum, the wall that separates the left and right atria of the heart. The most common physiological outcome of an ASD is a left-to-right shunt, which occurs due to the pressure differences between the two atria.

In a normal heart, the left atrium has a higher pressure due to the systemic circulation, while the right atrium is under lower pressure as it receives deoxygenated blood returning from the body. When there is a defect in the atrial septum, oxygen-rich blood from the left atrium can flow into the right atrium. This left-to-right shunting results in increased blood flow to the right atrium and subsequently to the right ventricle and pulmonary circulation.

Over time, this abnormal flow can lead to volume overload of the right heart and the pulmonary vessels, potentially resulting in complications such as pulmonary hypertension and right heart failure. Therefore, the characteristic shunt associated with ASDs is correctly identified as left to right, making this the appropriate choice.

Other types of blood shunts, such as right-to-left, typically occur in conditions like tetralogy of Fallot or during episodes