May Be Caused by

 Common

Atrial septal defect

Congenital heart disease

Cyanotic admixture lesion

Hilar lymphadenopathy

Patent ductus arteriosus

Pulmonary arterial hypertension

Pulmonary embolism

Pulmonary venous hypertension

Systemic-to-pulmonary vascular shunt

Truncus arteriosus type 1

Ventricular septal defect

 Uncommon

Polycythemia