Total anomalous pulmonary venous return
 Discussion of Total anomalous pulmonary venous return
- Anomalous pulmonary venous return (APVR) occurs when the pulmonary veins fail to drain into the left atrium and instead form an aberrant connection with some other cardiovascular structure.
- Such abnormalities account for approximately 2% of cardiac malformations.
- All the systemic venous and pulmonary venous blood enters the right heart, and the only path for its exit to the left heart is a communication in the atrial septum, usually a large atrial septal defect or patent foramen ovale (right-to-left shunt is essential for survival).
- The right heart is prominent in TAPVR because of the increased flow volume, but the left atrium remains normal in size.
- In infants affected by TAPVR, cyanosis and congestive heart failure typically develop in the early neonatal period.
- Approximately one-third of those with TAPVR also have other associated cardiac lesions; many have heterotaxy syndrome, particularly asplenia.
- Four types of TAPVR thus may be defined (in decreasing order of frequency)
- In type I, the anomalous pulmonary veins terminate at the supracardiac level. On chest radiographs, this cardiovascular anomaly resembles a snowman: The dilated vertical vein on the left, the innominate vein on the top, and the superior vena cava on the right form the head of the snowman; the body of the snowman is formed by the enlarged right atrium.
- Type II TAPVR involves a pulmonary venous connection at the cardiac level. The pulmonary veins join either the coronary sinus or the right atrium.
- Type III TAPVR involves a connection at the infracardiac or infradiaphragmatic level. The pulmonary veins join behind the left atrium to form a common vertical descending vein, which courses anterior to the esophagus and passes through the diaphragm at the esophageal hiatus. This vertical vein usually joins the portal venous system but occasionally connects directly to the ductus venosus, the hepatic veins, or the inferior vena cava.
- Type IV TAPVR involves anomalous venous connections at two or more levels.
 Imaging Findings for Total anomalous pulmonary venous return
- The radiologic appearance of TAPVR varies according to the site of abnormal venous drainage and whether the flow is obstructed.
- The structure in which the anomalous vein terminates appears dilated; termination at the level of the coronary sinus, superior vena cava, or azygos vein leads to dilatation of that structure and produces characteristic abnormalities in the imaging appearance.
- See above for imaging appearance of type I TAPVR
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 References for Total anomalous pulmonary venous return
- Emma C. Ferguson, Rajesh Krishnamurthy, and Sandra A. A. Oldham. Classic Imaging Signs of Congenital Cardiovascular Abnormalities. RadioGraphics 2007 27: 1323-1334.