What Are the Types of TAPVR?
Total anomalous pulmonary venous return is classified into different types. This is based on how and where the pulmonary veins drain to the heart:
Supracardiac Total Anomalous Pulmonary Venous Return
The pulmonary veins drain to the right atrium by the superior vena cava. In this type of TAPVR, the pulmonary veins come together behind the heart and then drain upwards into an abnormal “vertical vein.” This vertical vein joins the innominate vein, which connects to the right superior vena cava and drains to the right atrium.
Cardiac Total Anomalous Pulmonary Venous Return
The pulmonary veins come together behind the heart. They then drain to the right atrium through the coronary sinus. The coronary sinus is the vein that normally returns blood from the heart muscle itself back to the right atrium after its oxygen has been used. The coronary sinus drains directly into the right atrium.
Infracardiac Total Anomalous Pulmonary Venous Return
The pulmonary veins drain to the right atrium by the hepatic (liver) veins and inferior vena cava. In this type, the pulmonary veins join behind the heart. They then drain downwards into an abnormal “vertical vein,” connecting to the inferior vena cava or the liver's portal vein system. They then drain through the vascular bed of the liver and enter the right atrium from the hepatic veins.
In some cases, there are features of multiple types where different pulmonary veins have different types of drainage. This is called mixed TAPVR.
All types of total anomalous pulmonary venous return must have an atrial septal defect (ASD). An ASD is a hole in the wall between the right and left upper chambers of the heart. This hole will allow some of the oxygenated blood that has entered the right atrium from the pulmonary veins to go across to the left atrium and out to the body.
What Problems Are Associated With TAPVR?
Because of the abnormal pulmonary vein connection, oxygenated (red) blood returning from the lungs mixes with the less oxygenated (blue) blood returning from the body. The blood that then crosses the hole to the left side of the heart is filled only by mixed blood.
Because this blood is a mixture of oxygenated and deoxygenated (red and blue) blood, there is less oxygen in the blood leaving the heart and going to the body. This is why patients with TAPVR have low oxygen saturations.
If the atrial septal defect (ASD) is small or limits blood flow from the right atrium to the left atrium, then the volume of blood filling the left atrium and left ventricle may be lessened. This can lead to low blood supply to the body and shock.
In some cases of TAPVR, the route of blood from the pulmonary veins back to the heart may have areas of blockage or narrowing. This blockage may prevent a normal amount of blood return from the pulmonary veins and increase the pressure in the pulmonary veins. Blockage in the pulmonary veins leads to pulmonary edema in the lungs (excessive fluid or congestion) and pulmonary hypertension (high pressure in the lung vessels). Blocked pulmonary veins commonly happen in the infracardiac type of TAPVR. But it can happen with other types as well.
Patients with obstructed TAPVR are critically ill with severe cyanosis (low oxygen levels) and very unstable blood pressure. Surgery may be needed right away for these patients.
What Are the Symptoms of TAPVR?
Patients with obstructed (blocked) total anomalous pulmonary venous return are ill soon after birth. These children are severely cyanotic with blue coloring to skin, lips and nails. They also have respiratory problems including rapid breathing, grunting and retractions of the rib cage muscles.
If obstruction to pulmonary venous return is not present, children with TAPVR may not have many symptoms. There may be some fast breathing or mild difficulty breathing. While there is often cyanosis, it may be mild and hard to see.
Some children with TAPVR are diagnosed when a doctor hears a heart murmur during a physical examination. These children may not be diagnosed for several weeks to months.
