Partial and Total Anomalous Pulmonary Venous Connection

What is Partial and Total Anomalous Pulmonary Venous Connection?

In a healthy heart, fresh oxygen-filled blood from the lungs goes into the left chamber of the heart (the left atrium) via four or more blood vessels called pulmonary veins. At the same time, used blood, which doesn’t have a lot of oxygen, from the body gets into the right chamber of the heart (the right atrium) via the two large veins called the superior and inferior vena cava. However, in a condition called Partial Anomalous Pulmonary Venous Connections (PAPVC), one or more pulmonary veins incorrectly flow into the right atrium instead of the left. This could happen directly or by getting into the body’s veins.

There’s a more severe condition called Total Anomalous Pulmonary Venous Connection (TAPVC), a type of congenital heart defect which causes a blue tinge to the skin, lips and nails because of the lack of oxygen. Here, all the pulmonary veins drain into the right atrium of the heart, which is not normal.¹

What Causes Partial and Total Anomalous Pulmonary Venous Connection?

In order to fully understand the different types of heart and blood vessel abnormalities, it’s important to first understand how these structures normally develop in a fetus.

In the early stages of a baby’s development, the beginning stages of the lungs are surrounded by a network of blood vessels known as the splanchnic plexus. The common pulmonary vein, a blood vessel carrying oxygen-rich blood from the lungs back to the heart, forms as an outgrowth from the heart and establishes a connection between the heart and the lung’s blood vessels. After a while, this network of blood vessels gets simpler, with the common pulmonary vein essentially becoming a part of the left atrium, the left upper chamber of the heart, and four separate vessels connecting the lungs directly to this chamber. If the common pulmonary vein doesn’t develop normally and connections between the lung and body’s blood vessels persist, a condition called TAPVC can develop. Similarly, if just a part of the common pulmonary vein doesn’t form properly, a condition known as PAPVC can occur.

Usually, each lung has two blood vessels that drain into the back wall of the heart. However, sometimes, these vessels may join together and exit through one opening, or there may be several smaller branches from the vessels, each draining a smaller part of the lung but all connecting to the left atrium in the heart.

In rare cases, the lung’s blood vessels connect abnormally to the body’s blood vessels, or the vessels may connect to the right place but due to a defect within the heart, the oxygen-rich and oxygen-poor blood mix together. In the latter case, the lung’s blood vessels end up draining into the right atrium instead of the left.

A common type of PAPVC is when the upper left lung’s blood vessel drains into a vessel that carries blood to the right atrium. This condition can also present in various forms, with lung vessels draining into different parts of the body’s blood vessels.

A specific variant of PAPVC called Scimitar Syndrome is when parts or the entirety of the right lung drains into the IVC, a large vein that carries oxygen-poor blood from the lower half of the body to the heart. The affected lung sections may be underdeveloped or have bronchial anomalies and this syndrome can occur with other heart defects. Infants with these conditions often fare worse than adults and children and might also have high blood pressure in the lungs. In a chest x-ray, the abnormal blood vessel can be seen running parallel to the right border of the heart, resembling a Turkish sword, or “scimitar.”

Sinus venosus atrial septal defects occur when there’s no partition between the blood vessel of the right lung and a large vein that carries deoxygenated blood toward the heart, resulting in the lung vein’s oxygen-rich blood mixing in with the body’s oxygen-poor blood. The veins of the right lung are normally connected to the left atrium of the heart.

Another abnormality is when a wall within the heart, known as the septum primum, moves left of the openings of the right lung’s blood vessels, causing these vessels to drain into the right upper chamber of the heart. This is commonly seen in individuals with an abnormal arrangement of internal organs.

In TAPVC, all lung vessels connect to the body’s blood vessels or the right atrium, either through a common vein or individually. There are four subtypes of TAPVC distinguished by where the abnormal connection occurs: above the heart (supracardiac), within the heart (cardiac), below the heart (infracardiac), and combinations of these (mixed). The most common type of TAPVC is the supracardiac form.

Risk Factors and Frequency for Partial and Total Anomalous Pulmonary Venous Connection

The medical conditions TAPVC and PAPVC are quite rare birth defects. They make up less than 1% of all heart diseases that are present at birth.

Signs and Symptoms of Partial and Total Anomalous Pulmonary Venous Connection

Partial anomalous pulmonary venous connection (PAPVC) is a condition that affects the flow of blood from the lungs to the heart. It can present in many ways, often similar to atrial septal defect (ASD), a hole in the wall between the heart’s upper chambers. The symptoms and severity of PAPVC largely depend on how much blood is incorrectly flowing from the left to the right side of the heart, as well as if there are any associated heart defects. Turner’s syndrome patients, for example, often have a higher incidence of PAPVC.

When PAPVC is associated with an ASD, people with a minor shunt (improper blood flow) often have no symptoms and the condition might be discovered due to a heart murmur found during a routine physical exam. Those with a moderate to large shunt often start showing symptoms like shortness of breath and fatigue during childhood, which can progress to heart failure symptoms by their thirties or forties. While a portion of patients may develop significant pulmonary hypertension and subsequent cyanosis if left untreated, the physical exam findings are generally similar to those seen in ASD, such as a wide split in the second heart sound (S2) and a systolic murmur.

In cases of isolated PAPVC, where only one pulmonary vein is affected, it’s often not clinically significant. For those with multiple anomalous veins, the presentation largely hinges on the extent of the left-to-right shunt, and it’s quite similar to the presentations of ASD and PAPVC with ASD.

Total anomalous pulmonary venous connection (TAPVC) is another related condition that can present with or without pulmonary venous obstruction. Initially, patients may not show symptoms at birth. However, symptoms like shortness of breath, feeding difficulties, and failure to thrive often begin in the first few days of life due to excessive blood circulation in the lungs. The degree of cyanosis, or bluish discoloration of the skin, can vary. Right ventricular hypertrophy (enlargement or thickening of the heart’s right ventricle) and signs of right ventricular failure can develop later. Physical exams may reveal findings similar to those seen in PAPVC with ASD.

TAPVC patients with obstruction typically present severe respiratory distress and cyanosis at birth. Common physical findings include low oxygen levels, low blood pressure, and rapid breathing. This condition is often included in the diagnosis of newborns with persistent pulmonary hypertension. These newborns are often severely ill and require urgent surgical intervention.

While TAPVC usually presents as a lone defect, it can be associated with other congenital heart defects. It’s more commonly seen in patients with heterotaxy, a condition where the internal organs are abnormally arranged, with either multiple spleens (polysplenia) or absence of a spleen (asplenia).

Testing for Partial and Total Anomalous Pulmonary Venous Connection

When diagnosing conditions related to the pulmonary veins (the blood vessels that carry blood from the lungs to the heart), doctors use a variety of methods:

For a condition known as PAPVC, diagnosis can involve several tests:

– Electrocardiography (or ECG for short) is a test that checks your heart’s rhythm and electrical activity. Symptoms that may show up on an ECG include unusual heart rhythms or signs of an enlarged right atrium (the top right chamber of the heart).

– Chest radiography, or a chest x-ray, can also be used. This type of imaging allows doctors to see if your heart is larger than normal, or if the blood vessels in your lungs are more pronounced.

– Echocardiography uses sound waves to create images of your heart. This method can provide a highly detailed look at the structure and function of your pulmonary veins.

– Other methods, such as computed tomography (CT) and magnetic resonance imaging (MRI), can provide additional detail about the exact path of the pulmonary veins.

– Cardiac catheterization, a procedure that involves threading a long, thin tube (called a catheter) into your heart through a blood vessel, can provide a definitive diagnosis. However, with the recent advancements in non-invasive imaging methods, it is often not needed.

For TAPVC, another condition related to the pulmonary veins, the tests are quite similar:

– An ECG can reveal an unusual heart rhythm and signs of an enlarged right atrium or ventricle (the bottom right chamber of the heart).

– A chest x-ray can show if your heart is larger than normal, or if there are signs of fluid buildup in the lungs.

– Echocardiography is used to get images of the pulmonary veins and the path they take, and to check for any blockages or other problems with blood flow. This also allows doctors to examine the right atrium and ventricle and look for signs of them being overworked.

– CT and MRI scans can also be used, but these are generally reserved for cases where the echocardiography results are unclear.

– As with PAPVC, cardiac catheterization can be undertaken in more complex cases to gather additional information, or in cases where other treatments like the widening of a narrow pulmonary vein are needed.

Treatment Options for Partial and Total Anomalous Pulmonary Venous Connection

With Partial Anomalous Pulmonary Venous Connection (PAPVC), which is a condition where one or more, but not all, pulmonary veins drain into the right atrium instead of the left, the need for surgery depends on symptoms, the presence of a significant left to right shunt (a condition that allows blood to flow from the left side of heart to the right, potentially causing too much blood to reach the lungs), or evidence of right ventricular dysfunction (a condition that affects the lower right chamber of the heart). If these factors are not present, patients can usually be monitored without surgery. However, most patients with PAPVC of the sinus venosus type will likely need surgery between the ages of 2 and 4. If only one vein drains abnormally, they might not need any intervention at all in their lifetime.

Surgery procedures can differ, depending on the specific anatomy of the patient and any other heart problems that might be present.

On the other hand, Total Anomalous Pulmonary Venous Connection (TAPVC), where all four pulmonary veins drain into the right atrium, surgery is pretty much always needed, as soon as the patient is stable enough for the operation. Before surgery, patients may be given extra oxygen, or mechanical ventilation may be used to help with breathing. Sometimes, in severe cases, a balloon atrial septostomy (a procedure to enlarge the hole connecting the left and right atria of the heart) might be needed. In cases where TAPVC is obstructive, stents (tiny mesh tubes that prop open blood vessels) might be used to help stabilize the patient, but this isn’t a common solution.

Different surgical approaches might be used, depending on where the pulmonary veins connect. For example, if the veins connect to the coronary sinus (a collection of veins joined together to form a large vessel that collects blood from the heart muscle), one approach is to remove the wall between the sinus and the left atrium (the heart’s left upper chamber) to allow the blood from the pulmonary veins to reach the left atrium. Also, any atrial septal defects (holes in the wall between the heart’s upper chambers) are typically closed in the process.

If the veins connect above or below the heart (known as supracardiac and infracardiac types), a connection is created between the left atrium and the group of connected pulmonary veins. The vertical vein, which carries blood from the left atrium to the subclavian vein before it enters the right atrium, is usually tied off, unless severe lung hypertension (high blood pressure in the arteries of the lungs) is present. Various other techniques, including rerouting within the atrium, can also be used for more complex cases of TAPVC.

What else can Partial and Total Anomalous Pulmonary Venous Connection be?

It can sometimes be challenging to differentiate between ASD (Hole in the heart) and PAPVC (when some pulmonary veins connect to the right side of the heart instead of the left) in children, as most of them don’t show symptoms. Medical imaging techniques are useful for making an accurate diagnosis. A condition called ‘Single Atrium’, where the two upper chambers of the heart fail to separate, can also show symptoms similar to PAPVC.

While dealing with TAPVC (when all four pulmonary veins are connected abnormally), there are other conditions that should be ruled out. These can be categorized into obstructed and unobstructed TAPVC:

• Obstructed TAPVC where typical conditions could be:
  • Respiratory Distress Syndrome which usually starts showing signs right after birth which is unlike TAPVC that typically starts showing signs after the first 12 hours of life.
  • Persistent hypertension in the lungs of the newborn
• Unobstructed TAPVC could be confused with:
  • Large ASD, VSD (heart defects where there are holes in the walls of the heart)
  • Truncus arteriosus (a rare type of heart disease)
  • AV canal defects (defects that occur in the structures in the center of the heart)
  • Single ventricle lesions (a condition where either the left or right ventricle is underdeveloped)

What to expect with Partial and Total Anomalous Pulmonary Venous Connection

PAPVC

People with a single abnormal vein and a normal septum between the chambers of their heart (atria) usually don’t show any symptoms. If left untreated, larger shifts of blood from the left to the right side of the heart can lead to changes in the vessels in the lungs and develop into high blood pressure within these vessels (pulmonary hypertension).

The surgical correction of PAPVC generally works well, with a low rate of complications and typically an immediate relief from symptoms. However, babies with Scimitar syndrome face worse outcomes as a result of more complex heart structure and the existence of other heart issues.

TAPVC

If TAVPC remains untreated, it is usually fatal within the first few weeks of life. However, thanks to advancements in medical care and surgical procedures, long-term survival for patients with TAPVC has improved.

Postoperative Course

There are certain risk factors for increased mortality after the surgery such as being at a younger age when undergoing the operation, having other accompanying heart conditions, underdeveloped pulmonary veins, high blood pressure within the lungs after the surgery, and blockage of blood flow in the veins that carry oxygen-rich blood from the lungs to the heart (pulmonary venous obstruction) after the surgery.

Possible Complications When Diagnosed with Partial and Total Anomalous Pulmonary Venous Connection

PAPVC

If PAPVC, or Partial Anomalous Pulmonary Venous Connection, is left untreated, it can cause high blood pressure in the lungs and failure of the right side of the heart over time.

TAPVC

Following surgery for TAPVC, or Total Anomalous Pulmonary Venous Connection, complications may include high blood pressure in the lungs, irregular heartbeats, PVO (Pulmonary Venous Obstruction), and trouble coming off the heart-lung machine used during surgery.

Postoperative PVO

• Pulmonary Venous Obstruction (PVO) is a serious risk after TAPVC surgery. It is one of the main reasons why patients need to go back into surgery.
• The chances of survival drop to around 60% after 3 years if PVO happens post-surgery.
• Risk factors before surgery include underdeveloped pulmonary veins and mixed or abnormal connections in the lung.
• It is crucial to keep a close eye on these patients with regular check-ups because of these risks.

Preventing Partial and Total Anomalous Pulmonary Venous Connection

Parents and caregivers need to be informed about certain symptoms to look out for in their child. These symptoms may include quick breathing (tachypnea), problems with eating (feeding intolerance), and a bluish tint to the skin (cyanosis). If any of these signs are noticed, it’s necessary to seek immediate medical help. When a diagnosis is made, they should be made aware of the different treatment choices available. It’s also important to understand the risks and benefits associated with each treatment option, as well as potential long-term health issues (morbidity), potential risk of death (mortality), and the necessity for regular check-ups in the future.