What is TAPVC? Cardiology Basics

What is TAPVC? Cardiology Basics

TAPVC stands for total anomalous pulmonary venous connection. It is also known as TAPVD or total anomalous pulmonary venous drainage. Normally, pulmonary veins join the left atrium. When it drains to the right atrium through one of the blood vessels leading to the right atrium, it is known as TAPVC. If only some of the four pulmonary veins join the right side of the heart, then it is called PAPVC or partial anomalous pulmonary venous connection.

When all the pulmonary veins join the right side of the heart instead of the left side, an atrial septal defect (ASD) is needed to maintain life. Otherwise body will not get any oxygenated blood. Oxygenated blood returning from the lungs to the right side of the heart gets pumped back to the lungs. If there is no ASD, the left ventricle may not get any blood to pump at all! Blood returning from the body to the right side of the heart also will get pumped to the lungs.

Due to the mixing of oxygenated and deoxygenated blood in the right atrium, the blood pumped out into the body is desaturated. This produces cyanosis of lips, tongue, and skin. Thus, TAPVC is a cyanotic congenital heart disease. Part of the blood returning from the lungs can get recirculated to the lungs, increasing the pulmonary blood flow. Increased pulmonary blood flow can cause pulmonary hypertension in the long run.

There are basically four types of TAPVC. Most common variety is supracardiac. In supracardiac TAPVC, four pulmonary veins from the two lungs join together to form a common venous chamber behind the left atrium and drains upwards into a vertical vein. As the name implies, it runs vertically upwards from behind the left atrium, to left brachiocephalic vein. Brachiocephalic vein then joins the superior vena cava (SVC). SVC in turn drains to the right atrium.

The combination of vertical vein, dilated brachiocephalic vein and superior vena cava produce the classical figure of 8 shadow along with cardiac shadow on chest X-ray. Other descriptions are ‘snow man in snow storm’ appearance and ‘cottage loaf’ appearance. ‘Snow storm’ is the pulmonary plethora along with the supracardiac shadow.

In intracardiac variety of TAPVC, all four pulmonary veins drain into common venous chamber which drains into the coronary sinus. Common venous chamber can be seen behind the left atrium on echocardiography. Opening of pulmonary veins to the left atrium will not be seen. Drainage can be traced to the coronary sinus instead.

Next is the infracardiac variety, in which pulmonary veins go below the diaphragm. The pulmonary veins then join portal vein in the liver and drains to the inferior vena cava. There is also a fourth mixed type, which is much less common.

In the infracardiac variety, as the pulmonary venous return passes through the liver, the flow is partially obstructed (obstructed TAPVC). This increases pressure in the pulmonary capillaries leading to pulmonary edema and causes severe breathlessness in the baby, in addition to cyanosis. That will be a life threatening situation needing emergency treatment. Obstruction can also occur in supracardiac variety due to compression between pulmonary artery and left bronchus.

TAPVC with large ASD can survive long without much symptoms, but those with small ASD need emergency surgery. Initial procedure can be enlargement of the ASD by a procedure known as balloon atrial septostomy. Balloon atrial septostomy uses balloon catheters, usually introduced through the umbilical vein. The baby is then considered for corrective surgery after stabilization of medical status. Those with infracardiac variety will need emergency corrective surgery because of severe breathlessness.  Those with large ASD also need elective surgical correction.