Case of total anomalous pulmonary venous return (TAPVR); a congenital cyanotic heart disease
The entire pulmonary venous flow is directed to the right atrium via SVC (i.e. all pulmonary veins to common pulmonary vein to vertical vein to innominate vein to SVC)
Right to left shunt (ASD) is present which is responsible for the cyanosis
The paratracheal shadow on the right is the prominent SVC and on the left is the vertical vein.
These prominent vessels along with the heart give a characteristic 'snowman' appearance; also referred to as 'figure of 8' sign. It is characteristic of TAPVR type I (supracardiac type)