A systemic-to-pulmonary shunt is a cardiac shunt which allows, or is designed to cause, blood to flow from the systemic circulation to the pulmonary circulation. This occurs when:

1. there is a passage between two or more of the great vessels; and,
2. systemic pressure is higher than pulmonic pressure and/or the shunt has a one-way valvular opening.

A systemic-to-pulmonary shunt functions as follows:

1. left-to-right in the absence of arterioventricular discordance.
2. right-to-left if the great vessels are transposed.

Cardiovascular system