Left-to-right shunt

Left-to-right shunting refers to the abnormal situation in which blood travels form the left side of the heart or the arterial circulation to to the right side. In patients with atrial septal defects, the circulation of blood flow may become altered due to an opening or hole in wall or septum that separates the left atrium and right atrium. Because the blood pressure is higher in the left atrium than in the right atrium, there is initially a change in the blood flow from left-to-right, referred to as left-to-right shunting. There may also be left-to-right shunting in patients with a ventricular septal defect and in those patients in which there is an anomalous connection between the great vessels.

A left-to-right shunt is a cardiac shunt which allows, or is designed to cause, blood to flow from the left heart to the right heart. This occurs when:

1. There is an opening or passage between the atria, ventricles, and/or great vessels; and,
2. The left heart pressure is higher than right heart pressure and/or the shunt has a one-way valvular opening.

1. Atrial septal defect
2. Ventricular septal defect
3. Anomalous connection between the great vessels

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