Abnormal development of the pulmonary veins may result in either partial or complete anomalous drainage back into the systemic venous circulation. In contrast, partial anomalous pulmonary venous return (PAPVR) is usually an acyanotic condition.
Total anomalous pulmonary venous return (TAPVR) is a congenital disorder characterized by total mixing of systemic venous blood and pulmonary venous blood within the heart. This complete mixing of venous blood produces cyanosis.
For patients with anomalous pulmonary venous return, echocardiography is the preferred examination.
The echocardiogram demonstrates an enlarged right ventricle and a small left atrium. It may also show the pattern of abnormal pulmonary venous connections. When the pattern of Doppler venous flow of the abdominal veins is obtained, the finding of venous flow away from the heart is pathognomonic of TAPVR below the diaphragm. Shunting occurs almost exclusively from right to left at the atrial level.
Electrocardiograms demonstrate right ventricular hypertrophy, usually a qR pattern in V3, R, and V1. The P waves are frequently tall and spiked.
TAPVR is a cyanotic lesion. Echocardiographic results usually confirm the diagnosis. MRI and fast CT are also useful for defining pulmonary venous drainage. With cardiac catheterization, the presence of anomalous pulmonary veins may be demonstrated by means of selective pulmonary arteriography.
Sometimes, in anomalous pulmonary venous return, echocardiographic views are limited, and MRI may be necessary.
There are 3 major clinical patterns of TAPVR:
Severe pulmonary venous obstruction
Early heart failure
Mildly symptomatic or asymptomatic TAPVR.
See the image below depicting TAPVR.
Anomalous pulmonary venous return (APVR). Types of total anomalous pulmonary venous connection.
The history, physical signs, and electrocardiographic and radiographic findings of PAPVR and TAPVR are similar to those seen in patients with an isolated ostium secundum atrial septal defect (ASD). In some cases, an anomalous vein that drains into the inferior vena cava appears on chest radiography as a crescentic shadow of vascular opacity (like a scimitar) along the right border of the cardiac silhouette (scimitar syndrome). In these patients, an associated ASD is not seen; rather, pulmonary sequestration and anomalous arterial supply to the affected lobe of the lung are encountered.