Exploring Inside a Snowman by Magnetic Resonance Imaging

Abstract

The snowman sign is a sign on a chest x-ray image that indicates a supra-cardiac type total anomalous pulmonary venous return (TAPVR).1 TAPVR is a serious congenital heart disease which occurs due to an abnormal development of the fetal heart. This leads to an inappropriate connection of all four pulmonary veins.1 TAPVR is a congenital left to right shunt disease where all four pulmonary veins are gathered into a vertical vein behind the left atrium. The vertical vein plays a role as a reservoir of oxygenated blood that drains into the right side system directly or via the left innominate vein. TAPVR causes neonatal death if there is no oxygenated blood shunting from the pulmonary venous circulation system to the systemic circulation system. Thus TAPVR is considered a critical congenital heart disease because an infant with TAPVR needs surgical correction early after birth to survive.2 The incidence of TAPVR accounts for 1-5% of all cardiovascular congenital heart disease.^3,4 TAPVR is classified into four types according to the location (level) of the target organ of blood drainage from the vertical vein. The four types of TAPVR are: 1) supra-cardiac type, 2) cardiac type, 3) infra-cardiac type and 4) mixed type.