‘Snowman’ or ‘cottage loaf’ heart shape due to total anomalous pulmonary venous drainage

This is a classic picture of the ‘snowman’ or ‘cottage loaf’ heart shape due to total anomalous pulmonary venous drainage into a left superior vena cava (SVC). The confluence of pulmonary veins joins behind the heart and enters the ascending limb of the left SVC which appears as a dilated vessel on the right of the upper mediastinal edge. This large venous flow enters the transverse crossing vein or innominate vein making the convex roof of the cottage loaf, and joins the right SVC causing dilatation of the left side of mediastinum. As one looks at this film, there is, beneath these venous shadows, the lower part of the cottage loaf made up of dilated right atrium and ventricular mass which is the right ventricle. There is considerable increase in the size of pulmonary vessel arteries and veins (pulmonary plethora). This is due to increased pulmonary blood flow shown throughout the lungs.

This is from a young adult and it is unusual to find this in an adult. The picture is pathogmonic. The patient presents with signs of large atrial septal defect with mild cyanosis from the obligatory right to left shunt at atrial level.