Pulmonary blood flow is decreased, the RV is hypertrophied, and unoxygenated blood enters the AO. Systolic pressures in the RV, LV, and AO are identical. Level of arterial desaturation is related to severity of the RV outflow tract obstruction. 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.