The heart is one of the first organs to function; it begins to beat from about 5 weeks of pregnancy. Normally after birth, 4 pulmonary veins return oxygenated blood from the lungs to the heart’s left side. This blood is then pumped by the heart to the rest of the body.
During pregnancy, when the future baby’s heart is developing, abnormalities in the heart’s development can occur. One of these abnormalities is total anomalous pulmonary venous connection/drainage (TAPVC) where the 4 pulmonary veins do not drain into the heart’s left side.
Patients with TAPVC because of the abnormal internal anatomy may on chest X-ray have an appearance akin to a cottage loaf – cottage loaf sign.
Reference:Somerville J, Grech V. The chest x-ray in congenital heart disease 1. Total anomalous pulmonary venous drainage and coarctation of the aorta. Images Paediatr Cardiol, 2009 11(1):7–9. Go to reference
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Panel A ‘Cottage loaf’, ‘snowman’ or ‘figure of 8’ heart shape due to total anomalous pulmonary venous drainage, image reproduced with kind permission of the Images in Pediatric Cardiology journal. Panel B Outline of cottage loaf. Panel C Cottage loaf (a rustic traditional English loaf of bread made with yeast and white flour) consisting of two parts, the upper part is smaller than the lower part, image from Wikimedia Commons the free media repository.