Total anomalous pulmonary venous return (TAPVR) (pronounced TOHT-l uh-NOM-uh-luh-s PUHL-muh-ner-ee VEE-nuh-s ri-TURN), or connection (TAPVC) is a birth defect of the heart in which the veins bringing blood back from the lungs (pulmonary veins) don’t connect to the left atrium like usual. Instead they go to the heart by way of an abnormal (anomalous) connection.

What is Total Anomalous Pulmonary Venous Return

Total anomalous pulmonary venous return (TAPVR) is a birth defect of the heart. In a baby with TAPVR, oxygen-rich blood does not return from the lungs to the left atrium. Instead, the oxygen-rich blood returns to the right side of the heart. Here, oxygen-rich blood mixes with oxygen-poor blood. This causes the baby to get less oxygen than is needed to the body. To survive with this defect, babies with TAPVR usually have a hole between the right atrium and the left atrium (an atrial septal defect) that allows the mixed blood to get to the left side of the heart and pumped out to the rest of the body. Some children can have other heart defects along with TAPVR, aside from the atrial septal defect. Because a baby with this defect may need surgery or other procedures soon after birth, TAPVR is considered a critical congenital heart defect. Congenital means present at birth.

In a related defect, partial anomalous pulmonary venous return (PAPVR), not all of the veins have an abnormal connection. There are some abnormal connections, but one or more of the veins return normally to the left atrium. Therefore, PAPVR is not as critical as TAPVR.

In a baby without a congenital heart defect, the right side of the heart pumps oxygen-poor blood from the heart to the lungs through the pulmonary artery. The blood that comes back from the lungs is oxygen-rich, and it moves through the pulmonary veins to the left atrium. The left side of the heart pumps oxygen-rich blood to the rest of the body through the aorta.

The heart is an organ, about the size of a fist. It is made of muscle and pumps blood through the body. Blood is carried through the body in blood vessels, or tubes, called arteries and veins. The process of moving blood through the body is called circulation. Together, the heart and vessels make up the cardiovascular system.

Structure of the Heart

The heart has four chambers (two atria and two ventricles). There is a wall (septum) between the two atria and another wall between the two ventricles. Arteries and veins go into and out of the heart. Arteries carry blood away from the heart and veins carry blood to the heart. The flow of blood through the vessels and chambers of the heart is controlled by valves.

Blood Flow Through the Heart

(Abbreviations refer to labels in the illustration)

The heart pumps blood to all parts of the body. Blood provides oxygen and nutrients to the body and removes carbon dioxide and wastes. As blood travels through the body, oxygen is used up, and the blood becomes oxygen poor.

1. Oxygen-poor blood returns from the body to the heart through the superior vena cava (SVC) and inferior vena cava (IVC), the two main veins that bring blood back to the heart.
2. The oxygen-poor blood enters the right atrium (RA), or the right upper chamber of the heart.
3. From there, the blood flows through the tricuspid valve (TV) into the right ventricle (RV), or the right lower chamber of the heart.
4. The right ventricle (RV) pumps oxygen-poor blood through the pulmonary valve (PV) into the main pulmonary artery (MPA).
5. From there, the blood flows through the right and left pulmonary arteries into the lungs.
6. In the lungs, oxygen is put into the blood and carbon dioxide is taken out of the blood during the process of breathing. After the blood gets oxygen in the lungs, it is called oxygen-rich blood.
7. Oxygen-rich blood flows from the lungs back into the left atrium (LA), or the left upper chamber of the heart, through four pulmonary veins.
8. Oxygen-rich blood then flows through the mitral valve (MV) into the left ventricle (LV), or the left lower chamber.
9. The left ventricle (LV) pumps the oxygen-rich blood through the aortic valve (AoV) into the aorta (Ao), the main artery that takes oxygen-rich blood out to the rest of the body.

Heart: Heart Defects

One very common form of interatrial septum pathology is patent foramen ovale, which occurs when the septum primum does not close at birth, and the fossa ovalis is unable to fuse. The word patent is from the Latin root patens for “open.” It may be benign or asymptomatic, perhaps never being diagnosed, or in extreme cases, it may require surgical repair to close the opening permanently. As much as 20–25 percent of the general population may have a patent foramen ovale, but fortunately, most have the benign, asymptomatic version. Patent foramen ovale is normally detected by auscultation of a heart murmur (an abnormal heart sound) and confirmed by imaging with an echocardiogram. Despite its prevalence in the general population, the causes of patent ovale are unknown, and there are no known risk factors. In nonlife-threatening cases, it is better to monitor the condition than to risk heart surgery to repair and seal the opening.

Coarctation of the aorta is a congenital abnormal narrowing of the aorta that is normally located at the insertion of the ligamentum arteriosum, the remnant of the fetal shunt called the ductus arteriosus. If severe, this condition drastically restricts blood flow through the primary systemic artery, which is life threatening. In some individuals, the condition may be fairly benign and not detected until later in life. Detectable symptoms in an infant include difficulty breathing, poor appetite, trouble feeding, or failure to thrive. In older individuals, symptoms include dizziness, fainting, shortness of breath, chest pain, fatigue, headache, and nosebleeds. Treatment involves surgery to resect (remove) the affected region or angioplasty to open the abnormally narrow passageway. Studies have shown that the earlier the surgery is performed, the better the chance of survival.

A patent ductus arteriosus is a congenital condition in which the ductus arteriosus fails to close. The condition may range from severe to benign. Failure of the ductus arteriosus to close results in blood flowing from the higher pressure aorta into the lower pressure pulmonary trunk. This additional fluid moving toward the lungs increases pulmonary pressure and makes respiration difficult. Symptoms include shortness of breath (dyspnea), tachycardia, enlarged heart, a widened pulse pressure, and poor weight gain in infants. Treatments include surgical closure (ligation), manual closure using platinum coils or specialized mesh inserted via the femoral artery or vein, or nonsteroidal anti-inflammatory drugs to block the synthesis of prostaglandin E2, which maintains the vessel in an open position. If untreated, the condition can result in congestive heart failure.

Septal defects are not uncommon in individuals and may be congenital or caused by various disease processes. Tetralogy of Fallot is a congenital condition that may also occur from exposure to unknown environmental factors; it occurs when there is an opening in the interventricular septum caused by blockage of the pulmonary trunk, normally at the pulmonary semilunar valve. This allows blood that is relatively low in oxygen from the right ventricle to flow into the left ventricle and mix with the blood that is relatively high in oxygen. Symptoms include a distinct heart murmur, low blood oxygen percent saturation, dyspnea or difficulty in breathing, polycythemia, broadening (clubbing) of the fingers and toes, and in children, difficulty in feeding or failure to grow and develop. It is the most common cause of cyanosis following birth. The term “tetralogy” is derived from the four components of the condition, although only three may be present in an individual patient: pulmonary infundibular stenosis (rigidity of the pulmonary valve), overriding aorta (the aorta is shifted above both ventricles), ventricular septal defect (opening), and right ventricular hypertrophy (enlargement of the right ventricle). Other heart defects may also accompany this condition, which is typically confirmed by echocardiography imaging. Tetralogy of Fallot occurs in approximately 400 out of one million live births. Normal treatment involves extensive surgical repair, including the use of stents to redirect blood flow and replacement of valves and patches to repair the septal defect, but the condition has a relatively high mortality. Survival rates are currently 75 percent during the first year of life; 60 percent by 4 years of age; 30 percent by 10 years; and 5 percent by 40 years.

In the case of severe septal defects, including both tetralogy of Fallot and patent foramen ovale, failure of the heart to develop properly can lead to a condition commonly known as a “blue baby.” Regardless of normal skin pigmentation, individuals with this condition have an insufficient supply of oxygenated blood, which leads to cyanosis, a blue or purple coloration of the skin, especially when active.

Septal defects are commonly first detected through auscultation, listening to the chest using a stethoscope. In this case, instead of hearing normal heart sounds attributed to the flow of blood and closing of heart valves, unusual heart sounds may be detected. This is often followed by medical imaging to confirm or rule out a diagnosis. In many cases, treatment may not be needed. Some common congenital heart defects are illustrated in Figure.

Figure. Congenital Heart Defects (a) A patent foramen ovale defect is an abnormal opening in the interatrial septum, or more commonly, a failure of the foramen ovale to close. (b) Coarctation of the aorta is an abnormal narrowing of the aorta. (c) A patent ductus arteriosus is the failure of the ductus arteriosus to close. (d) Tetralogy of Fallot includes an abnormal opening in the interventricular septum.

During prenatal development, the fetal circulatory system is integrated with the placenta via the umbilical cord so that the fetus receives both oxygen and nutrients from the placenta. However, after childbirth, the umbilical cord is severed, and the newborn’s circulatory system must be reconfigured. When the heart first forms in the embryo, it exists as two parallel tubes derived from mesoderm and lined with endothelium, which then fuse together. As the embryo develops into a fetus, the tube-shaped heart folds and further differentiates into the four chambers present in a mature heart. Unlike a mature cardiovascular system, however, the fetal cardiovascular system also includes circulatory shortcuts, or shunts. A shunt is an anatomical (or sometimes surgical) diversion that allows blood flow to bypass immature organs such as the lungs and liver until childbirth.

The placenta provides the fetus with necessary oxygen and nutrients via the umbilical vein. (Remember that veins carry blood toward the heart. In this case, the blood flowing to the fetal heart is oxygenated because it comes from the placenta. The respiratory system is immature and cannot yet oxygenate blood on its own.) From the umbilical vein, the oxygenated blood flows toward the inferior vena cava, all but bypassing the immature liver, via the ductus venosus shunt (image). The liver receives just a trickle of blood, which is all that it needs in its immature, semifunctional state. Blood flows from the inferior vena cava to the right atrium, mixing with fetal venous blood along the way.

Although the fetal liver is semifunctional, the fetal lungs are nonfunctional. The fetal circulation therefore bypasses the lungs by shifting some of the blood through the foramen ovale, a shunt that directly connects the right and left atria and avoids the pulmonary trunk altogether. Most of the rest of the blood is pumped to the right ventricle, and from there, into the pulmonary trunk, which splits into pulmonary arteries. However, a shunt within the pulmonary artery, the ductus arteriosus, diverts a portion of this blood into the aorta. This ensures that only a small volume of oxygenated blood passes through the immature pulmonary circuit, which has only minor metabolic requirements. Blood vessels of uninflated lungs have high resistance to flow, a condition that encourages blood to flow to the aorta, which presents much lower resistance. The oxygenated blood moves through the foramen ovale into the left atrium, where it mixes with the now deoxygenated blood returning from the pulmonary circuit. This blood then moves into the left ventricle, where it is pumped into the aorta. Some of this blood moves through the coronary arteries into the myocardium, and some moves through the carotid arteries to the brain.

The descending aorta carries partially oxygenated and partially deoxygenated blood into the lower regions of the body. It eventually passes into the umbilical arteries through branches of the internal iliac arteries. The deoxygenated blood collects waste as it circulates through the fetal body and returns to the umbilical cord. Thus, the two umbilical arteries carry blood low in oxygen and high in carbon dioxide and fetal wastes. This blood is filtered through the placenta, where wastes diffuse into the maternal circulation. Oxygen and nutrients from the mother diffuse into the placenta and from there into the fetal blood, and the process repeats.

The heart folds quickly like origami and now starts beating. This begins with the formation of two tubes and beats spontaneously by week 4 of development.

Developing rapidly and early, the heart is the first organ to function in the embryo, and it takes up most of the room in the fetus's midsection in the first few weeks of its life. During its initial stages of development, the fetal heart actually resembles those of other animals. In its tubelike, two-chambered phase, the fetal heart resembles that of a fish. In its three-chambered phase, the heart looks like that of a frog. As the atria and then the ventricles start to separate, the human heart resembles that of a turtle, which has a partial septum in its ventricle. The final, four-chambered design is common to mammals and birds. The four chambers allow low-pressure circulation to the lungs and high pressure circulation to the rest of the body.

Development of the Heart

The human heart is the first functional organ to develop. It begins beating and pumping blood around day 21 or 22, a mere three weeks after fertilization. This emphasizes the critical nature of the heart in distributing blood through the vessels and the vital exchange of nutrients, oxygen, and wastes both to and from the developing baby. The critical early development of the heart is reflected by the prominent heart bulge that appears on the anterior surface of the embryo.

The heart forms from an embryonic tissue called mesoderm around 18 to 19 days after fertilization. Mesoderm is one of the three primary germ layers that differentiates early in development that collectively gives rise to all subsequent tissues and organs. The heart begins to develop near the head of the embryo in a region known as the cardiogenic area. Following chemical signals called factors from the underlying endoderm (another of the three primary germ layers), the cardiogenic area begins to form two strands called the cardiogenic cords (Figure 19.36). As the cardiogenic cords develop, a lumen rapidly develops within them. At this point, they are referred to as endocardial tubes. The two tubes migrate together and fuse to form a single primitive heart tube. The primitive heart tube quickly forms five distinct regions. From head to tail, these include the truncus arteriosus, bulbus cordis, primitive ventricle, primitive atrium, and the sinus venosus. Initially, all venous blood flows into the sinus venosus, and contractions propel the blood from tail to head, or from the sinus venosus to the truncus arteriosus. This is a very different pattern from that of an adult.

Development of the Human Heart This diagram outlines the embryological development of the human heart during the first eight weeks and the subsequent formation of the four heart chambers.

The five regions of the primitive heart tube develop into recognizable structures in a fully developed heart. The truncus arteriosus will eventually divide and give rise to the ascending aorta and pulmonary trunk. The bulbus cordis develops into the right ventricle. The primitive ventricle forms the left ventricle. The primitive atrium becomes the anterior portions of both the right and left atria, and the two auricles. The sinus venosus develops into the posterior portion of the right atrium, the SA node, and the coronary sinus.

As the primitive heart tube elongates, it begins to fold within the pericardium, eventually forming an S shape, which places the chambers and major vessels into an alignment similar to the adult heart. This process occurs between days 23 and 28. The remainder of the heart development pattern includes development of septa and valves, and remodeling of the actual chambers. Partitioning of the atria and ventricles by the interatrial septum, interventricular septum, and atrioventricular septum is complete by the end of the fifth week, although the fetal blood shunts remain until birth or shortly after. The atrioventricular valves form between weeks five and eight, and the semilunar valves form between weeks five and nine.

Almost all newborns in the United States are screened for congenital heart defects shortly after birth. However, if you are at high risk for having a baby with a congenital heart defect, your doctor may recommend screening before the baby is born or strategies to help prevent a congenital heart defect.

Screening before a baby is born

Echocardiography or echo is a painless test that uses sound waves to create moving pictures of the heart. Your doctor may recommend a fetal echocardiogram during pregnancy if your routine ultrasound shows any sign that your developing baby may have a heart defect or if you have risk factors for a congenital heart defect.

Newborn screenings

Pulse oximetry is a test that can tell whether a newborn has low levels of oxygen in the blood, which may be a symptoms of critical congenital heart defects. The test involves attaching sensors to the baby’s hands or feet to measure oxygen levels and is recommended for all newborns in the United States.

Low oxygen levels in the blood could be due to a congenital heart defect or could be a sign that something else is wrong. If your child has low oxygen levels, the doctor may repeat the test, or may run more tests to diagnose a congenital heart defect.

There are different types of TAPVR, based on where the pulmonary veins connect:

• Supracardiac– In supracardiac TAPVR, the pulmonary veins come together and form an abnormal connection above the heart to the superior vena cava, which is a main blood vessel that brings oxygen-poor blood from the upper part of the body to the heart. In this type of TAPVR, a mixture of oxygen-poor and oxygen-rich blood returns to the right atrium through the superior vena cava.
• Cardiac – In cardiac TAPVR, the pulmonary veins meet behind the heart and connect to the right atrium. The coronary sinus, which is a vein that helps bring oxygen-poor blood from the heart muscle back to the heart, helps connect the pulmonary veins to the right atrium in this type of TAPVR.
• Infracardiac – In infracardiac TAPVR, the pulmonary veins come together and form abnormal connections below the heart. A mixture of oxygen-poor blood and oxygen-rich blood returns to the right atrium from the veins of the liver and the inferior vena cava, which is the main blood vessel that brings oxygen-poor blood from the lower part of the body to the heart.

In a 2019 study using data from birth defects tracking systems across the United States, researchers estimated that each year about 504 babies in the United States are born with Total Anomalous Pulmonary Venous Return. In other words, about 1 in every 7,809 babies born in the United States each year are born with Total Anomalous Pulmonary Venous Return.

The causes of heart defects, such as TAPVR, among most babies are unknown. Some babies have heart defects because of changes in their genes or chromosomes. Heart defects also are thought to be caused by a combination of genes and other risk factors, such as the things the mother or fetus come in contact with in the environment or what the mother eats or drinks or the medicines she uses.

Diagnosis

TAPVR and PAPVR might be diagnosed during pregnancy, but more often these defects are diagnosed soon after a baby is born.

During Pregnancy

During pregnancy, there are screening tests (also called prenatal tests) to check for birth defects and other conditions. TAPVR might be diagnosed during pregnancy with an ultrasound (which creates pictures of the body). Some findings from the ultrasound may make the health care provider suspect a baby could have TAPVR. If so, the health care provider can request a fetal echocardiogram to confirm the diagnosis. A fetal echocardiogram is an ultrasound specifically of the baby’s heart and major blood vessels that is performed during the pregnancy. This test can show problems with the structure of the heart and how well the heart is working. However, TAPVR defect is not commonly detected during pregnancy. It is hard for doctors to see the pulmonary veins on the prenatal screening tests since not much blood goes to the lungs before the baby is born. It is easier to detect this defect after birth when the blood is flowing to the lungs and returning to the heart.

After a Baby is Born

Symptoms usually occur at birth or very soon afterwards. Infants with TAPVR can have a bluish looking skin color, called cyanosis, because their blood doesn’t carry enough oxygen. Infants with TAPVR or other conditions causing cyanosis can have symptoms such as:

• Problems breathing
• Pounding heart
• Weak pulse
• Ashen or bluish skin color
• Poor feeding
• Extreme sleepiness

Using a stethoscope, a doctor will often hear a heart murmur (an abnormal “whooshing” sound caused by blood flowing through the atrial septal defect). However, it is not uncommon for a heart murmur to be absent right at birth.

If a doctor suspects that there might be a problem, the doctor can request one or more tests to confirm the diagnosis of TAPVR. The most common test is an echocardiogram. This is an ultrasound of the heart that can show problems with the structure of the heart, like holes in the walls between the chambers, and any irregular blood flow. Cardiac catheterization also can confirm the diagnosis by showing that the blood vessels are abnormally attached. An electrocardiogram (EKG), which measures the electrical activity of the heart, chest x-rays, and other medical tests may also be used to make the diagnosis.

TAPVR is a critical congenital heart defect (critical CHD) that also can be detected with newborn pulse oximetry screening using pulse oximetry (also known as pulse ox). Pulse oximetry is a simple bedside test to determine the amount of oxygen in a baby’s blood. Low levels of oxygen in the blood can be a sign of a CCHD. Newborn screening using pulse oximetry can identify some infants with a CCHD, like TAPVR, before they show any symptoms.

Babies with TAPVR will need surgery to repair the defect. The age at which the surgery is done depends on how sick the child is and the specific structure of the abnormal connections between the pulmonary veins and the right atrium. The goal of the surgical repair of TAPVR is to restore normal blood flow through the heart. To repair this defect, doctors usually connect the pulmonary veins to the left atrium, close off any abnormal connections between blood vessels, and close the atrial septal defect.

Infants whose defects are surgically repaired are not cured; they may have lifelong complications. A child or adult with TAPVR will need regular follow-up visits with a cardiologist (a heart doctor) to monitor their progress, avoid complications, and check for other health conditions that might develop as they get older.