Total anomalous pulmonary venous return
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Total anomalous pulmonary venous return (TAPVR) is a cyanotic congenital heart anomaly with abnormal drainage anatomy of the entire pulmonary venous system. This contrasts with partial anomalous pulmonary venous return (PAPVR) where only part of the pulmonary venous anatomy is abnormal.
In TAPVR, all systemic and pulmonary venous blood enters the right atrium and nothing drains into the left atrium. A right-to-left shunt is required for survival and is usually via a large patent foramen ovale (PFO) or less commonly atrial septal defect (ASD).
Affected infants develop cyanosis and congestive heart failure in the early neonatal period.
The anomaly occurs secondary to an embryological failure of pulmonary venous development:
at the earliest stage of lung development, the primitive lung bud venous drainage occurs via the splanchnic plexus to primitive systemic (cardinal/umbilicovitelline) veins; at this point, the heart is still forming and there is no pulmonary connection
at 27 to 29 days of life, a common pulmonary vein begins growing outwards from the primitive left atrium to join the primitive pulmonary veins
the common pulmonary vein joins with the pulmonary veins from each lung, forming the familiar configuration; simultaneously, there is involution of the primitive connection between pulmonary veins and primitive systemic veins
Failure to completely transition between primitive and mature configurations according to this sequence results in persistent venous drainage from the lungs to one of several possible systemic veins (see Classification) 4.
TAPVR can be classified into four types (in decreasing order of frequency) depending on the site of anomalous venous union 1:
Type I: supracardiac
most common type (over 50% of cases)
anomalous pulmonary veins terminate at the supracardiac level
Type II: cardiac
second most common (~30% of cases)
pulmonary venous connection at the cardiac level
Type III: infracardiac
connection at the infracardiac level
the pulmonary veins join behind the left atrium to form a common vertical descending vein
the common descending vein courses anterior to the esophagus passes through the diaphragm at the esophageal hiatus and then usually join the portal system
Type IV: mixed pattern
least common type
anomalous venous connections at two or more levels
Other rare types
arises from failure of the common pulmonary vein to incorporate into the LA (around 30 days' gestation).
results in persisting connections between the primitive pulmonary venous plexus and the cardinal venous systems.
Approximately one-third of those with TAPVR also have other associated cardiac lesions; many have heterotaxy syndrome, particularly asplenia. Type III (infracardiac) is also associated with thoracic lymphangiectasia and pulmonary congestion.
The right heart is prominent in TAPVR because of the increased flow volume, but the left atrium remains normal in size. Types I and II result in cardiomegaly.
The supracardiac variant (type I) can classically depict a snowman appearance on a frontal chest radiograph, also known as figure of 8 heart or cottage loaf heart 2,3. The dilated vertical vein on the left, brachiocephalic vein on 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.
Transthoracic echocardiography may be used to define the anatomical connections present, as well as assess the hemodynamic consequences:
right sided pressure and volume overload
compressed left sided chambers
left atrium and ventricle typically diminutive and underfilled
dilation of the superior vena cava
commonly present in supracardiac types
dilation of the coronary sinus
color flow Doppler may demonstrate inflow from the common pulmonary vein and egress to the right atrium 5
dilation of the inferior vena cava 6
may be seen with infracardiac types
the vertical vein may be seen as it travels inferiorly to connect with e.g. the portal or hepatic veins
aliasing at the junction of the vessels indicative of turbulence typically secondary to obstruction
Direct visualization of anomalous venous return.