Total Anomalous Pulmonary Venous Return (TAPVR)?

What is Total Anomalous Pulmonary Venous Return (TAPVR)?The pulmonary veins are the four blood vessels (two on each side) that return oxygen-rich blood from the lungs to the left atrium of the heart.

Total Anomalous Pulmonary Venous Return (TAPVR) is a rare congenital malformation in which all four pulmonary veins do not connect normally to the left atrium, but instead drain abnormally to the right atrium by way of an abnormal (anomalous) connection.

Total Anomalous Pulmonary Venous Return is classified into different types, based on the location of the abnormal pulmonary vein connection:

A. Supracardiac Total Anomalous Pulmonary Venous Return -- The pulmonary veins drain to the right atrium via the superior vena cava. In this type of TAPRVR, the pulmonary veins come together behind the heart and then drain upwards to an abnormal vertical vein. This vein joins the innominate vein which connects to the right superior vena cava and drains to the right atrium.

B. Cardiac Total Anomalous Pulmonary Venous Return -- The pulmonary veins come together behind the heart and then drain 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 depleted. The coronary sinus drain directly into the right atrium.

C. Infracardiac Total Anomalous Pulmonary Venous Return -- The pulmonary veins drain to the right atrium via the hepatic (liver) veins and inferior vena cava. In this type, the pulmonary veins join together behind the heart and then typically drain downwards, connecting to 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.

Common to all types of Total Anomalous Pulmonary Venous Return is an atrial septal defect (ASD). Because none of the pulmonary veins connect normally to the left side of the heart (and thus out to the body) is shunted blood from the right atrium across the atrial septal defect. Absence of an atrial septal defect in Total Anomalous Pulmonary Venous Return is not compatible with survival.



Why Does Total Anomalous Pulmonary Venous Return Cause Problems?Diminished oxygen content of the arterial blood (cyanosis) and an increased volume load on the right ventricle characterize the physiology of Total Anomalous Pulmonary Venous Return.

Because of the abnormal pulmonary vein connection there is complete mixing together of the oxygenated blood returning from the lungs (in pulmonary veins) and the unoxygenated blood returning from the body (in the vena cavae).

The left atrium and left ventricle are filled only by blood shunting across an atrial septal defect (from right atrium to left atrium). Because this blood is a mixture of oxygenated and unoxygenated blood, the overall content in the blood ejected by the left ventricle to the aorta is decreased.

This explains why patients with Total Anomalous Pulmonary Venous Return have low arterial oxygen saturations (i.e. are cyanotic).

If the atrial septal defect is small or restrictive to blood flow from the right atrium, then the volume of blood filling the left atrium and left ventricle may be diminished. This can lead to low cardiac output and shock.

In some cases of Total Anomalous Pulmonary Venous Return, the route of blood from the pulmonary veins back to the heart may have areas of narrowing or obstruction. This obstruction may prevent adequate blood return from the pulmonary veins and may increase the pressure in the veins, leading to congestion in the lungs (pulmonary edema) and pulmonary hypertension. Patients with Obstructed Total Anomalous Pulmonary Venous Return are usually critically ill with severe cyanosis and often have marked hemodynamic instability. Emergent surgical intervention may be necessary in these cases.

Obstructed pulmonary veins most commonly occur in the infracardiac type of Total Anomalous Pulmonary Venous Return, although it can occur with other anatomic types as well.



Signs and symptoms
Patients with Total Anomalous Pulmonary Venous Return and obstructed pulmonary venous return are extremely ill soon after birth. These children are severely cyanotic. They also have respiratory distress, with rapid breathing, grunting and retractions of the rib cage muscles. Often such infants may be initially thought to have pneumonia or other respiratory diseases of the newborn, until an accurate cardiac diagnosis is made.

If obstruction to pulmonary venous return is not present, children with Total Anomalous Pulmonary Venous Return without obstructed pulmonary venous return may be asymptomatic. There may be mild to moderate rapid or labored breathing. There is often cyanosis, but it may be mild and difficult to detect.

Some children with this more common type of Total Anomalous Pulmonary Venous Return are first detected when a physician hears a heart murmur during a physical examination. It is not uncommon for these children to go undiagnosed for weeks to months.


Total Anomalous Pulmonary Venous Return evaluations and diagnosisThe diagnosis of Total Anomalous Pulmonary Venous Return may be initially suspected when a physician hears a typical heart murmur and detects evidence of right ventricular overload.

Measurement of oxygen saturation may detect a low value, typically in the mid-to-high 80s in children without pulmonary vein obstruction. An electrocardiogram will reveal evidence of right atrial and right ventricular enlargement.

A chest X-ray, similarly, will show heart enlargement and will also demonstrate increased pulmonary artery blood flow. In newborns with Total Anomalous Pulmonary Venous Return and obstructed pulmonary venous return, chest x-ray may show evidence of pulmonary edema.

The definitive diagnosis of Total Anomalous Pulmonary Venous Return is usually made by echocardiogram. This study will demonstrate the abnormal connection of the pulmonary veins, in a supracardiac, cardiac or infracardiac pattern.

Echocardiography also demonstrates enlargement of the right atrium and right ventricle and can assess the size of and flow across the atrial septal defect.

On occasion, cardiac catheterization is required to make a definite diagnosis of Total Anomalous Pulmonary Venous Return.

Cardiac catheterization will define the abnormal connection of all pulmonary veins, and is particularly helpful and unusual patterns of mixed Total Anomalous Pulmonary Venous Return (for example when some veins drain in a supracardiac and others in an infracardiac pattern in the same patient).

Cardiac catheterization can also determine accurately whether or not pulmonary veins are obstructed and if the atrial septal defect is restrictive. If so, a balloon dilation procedure can be performed to enlarge the defect, in turn allowing better shunting of blood from right to left atrium.


Total Anomalous Pulmonary Venous Return Treatments
Total anomalous pulmonary venous return is a defect which requires surgical correction. The timing of the surgical repair varies depending on the type of Total Anomalous Pulmonary Venous Return present, and the condition of the child.

Surgical repair is performed emergently in the newborn period for newborns with Total Anomalous Pulmonary Venous Return and obstructed pulmonary veins. This is typical for the infracardiac type. Some of these children will actually require extracorporeal life support (ECMO) prior to surgery because of their marked hemodynamic instability.

Total Anomalous Pulmonary Venous Return without obstruction to pulmonary vein return typically undergo surgical repair electively days or weeks after the diagnosis is made.

In these children, although the surgery is not emergent, there is generally little benefit to be gained by waiting more than one or two months.

Rarely, Total Anomalous Pulmonary Venous Return is complicated by a restrictive atrial septal defect. In these children, a balloon dilation procedure may be performed at cardiac catheterization to improve the child's condition prior to surgical repair.

In virtually all types of Total Anomalous Pulmonary Venous Return, the pulmonary veins return to a common confluence behind the left atrium. The surgical repair takes advantage of this fact. The common pulmonary vein confluence is connected by the surgeon to the back of the left atrium, resulting in a normal connection of pulmonary veins to left atrial chamber.

All other routes for pulmonary venous drainage, such as the abnormal vessels which had carried pulmonary vein blood to the supracardiac or infracardiac areas, are tied off.

Finally, the atrial septal defect is also closed. This surgical repair therefore results in a normal circulation: the pulmonary veins returning normally to the left atrium, without abnormal connections or septal defects.