Is TAPVR Hereditary & Which Type Is The Most Common?

The prevalence of TAPVR in the United States is around 6.8 per 100,000 live births. Infracardiac type TAPVR is mostly found in males with a male-female ratio of 3:1 (1).

Is TAPVR Hereditary?

Although there have been familial cases of TAPVR in the literature including siblings, there is no known definitive genetic transmission of the malformation. A monogenic pattern of inheritance has been suggested from different reported familial cases with single-gene disorders such as Holt-Oram syndrome, Ivemark syndrome, Noonan syndrome, and chromosomal alterations (22 partial trisomies). However, data from most of the cases are not sufficient to draw a conclusive remark regarding its hereditary predisposition (3).

There has been a possible association of TAPVR with environmental teratogens, such as exposure to lead or pesticides raising a doubt regarding familial susceptibility to certain environmental risk factors (1).

Which Type Of TAPVR Is Most Common?

According to Darling et al., TAPVR can be classified into four different types, which include:

Supracardiac Type: It is the most common type of TAPVR that is seen in 45% of all the TAPVR cases. The pulmonary veins connect to a remnant of the common pulmonary vein behind the left atrium and drain into the left innominate vein through the vertical vein and sometimes the vertical vein connects with the right superior vena cava, which is an uncommon event.

Cardiac And Coronary Sinus Type: It accounts for 25% of all the cases of TAPVR. All the pulmonary veins drain into a common vein connecting to the coronary sinus or right atrium.

Infracardiac Type: This type of connection is seen in 25% of the cases of TAPVR. The four pulmonary veins drain into a common pulmonary vein that travels through the diaphragm and connect to the intra-abdominal veins, which is mostly the portal vein and on rare occasions, it may drain into the hepatic veins, ductus venosus, gastric vein or inferior vena cava.

Mixed Type Of TAPVR: It consists of a mixture of super cardiac, cardiac, and Infracardiac TAPVR. Depending on the pattern, it is again divided into 2 most common subtypes that include 3+1 and 2+2 mixed TAPVR. In 3+1 mixed TAPVR, the two right pulmonary veins and lower left pulmonary vein drain into the right atrium while the left pulmonary vein drains into the left innominate vein through a vertical vein. In 2+2 mixed type, the two right pulmonary veins drain into the right atrium or coronary sinus and the two left pulmonary veins drain into the left innominate vein through a vertical vein (2).

Total Anomalous Pulmonary Venous Return (TAPVR) is a rare congenital cardiac defect seen in 1.5% of all patients with cardiovascular abnormalities, according to Baltimore-Washington Infant Study (1981-1987), with a regional prevalence of 6.8 infants per 100,000 live births.

Although in the Baltimore-Washington Infant Study, male to female ratio was 18:23, other studies showed strong male dominance with a male to female ratio of 3:1. TAPVR is an anomalous condition involving all 4 pulmonary veins, which instead of draining to the left atrium drain to the right side of the heart and systemic veins that may or may not be associated with pulmonary venous obstruction. The oxygenated blood of the pulmonary veins and systemic deoxygenated blood mix together in the right atrium that is associated with significant morbidity (1).

Management Of TAPVR

The management of TAPVR requires early diagnosis and emergency surgical correction of the defect as it is associated with increased mortality and morbidity if not surgically corrected. It is important to stabilize the patient by mechanical ventilation, inotropic drugs, diuretics, prostaglandin E for ductus arteriosus and ductus venosus, nitric oxide, magnesium sulfate and extracorporeal membrane oxygenation (ECMO) (1).

About 80% of the neonates with TAPVR die due to progressive congestive heart failure without any surgical intervention. However, the survival rate has reached around 97% after surgery. Therefore, it is important to diagnose the condition early and perform an emergency operation (3).