Unoxygenated blood returning to the right heart enters the AO, causing severe cyanosis.

Oxygenated blood returning to the LA enters the pulmonary circulation again. The RV is hypertrophied, and the foramen ovale permits minimal mixing. Atrial pressures are mean pressures.

AO = aorta; IVC = inferior vena cava; LA = left atrium; LV = left ventricle; PA = pulmonary artery; PV = pulmonary veins; RA = right atrium; RV = right ventricle; SVC = superior vena cava.