Pulmonary Atresia With Intact Ventricular Septum

Overview

Children with pulmonary atresia with intact ventricular septum (PA/IVS) are born without a functioning pulmonary valve, the valve between the heart’s lower right chamber (right ventricle) and the pulmonary artery, which leads to the lungs. When there's no hole between the chambers, it's known as an IVS. Without a functioning pulmonary valve, blood can’t flow properly from the heart’s right ventricle to the lungs. The wall between the two lower pumping chambers is completely formed. This means that blood that enters the right ventricle has no way to exit the pumping chamber directly. Since blood can’t exit the right side of the heart, it instead passes through a hole (an atrial septal defect [ASD] or patent foramen ovale [PFO]) in the wall that separates the heart’s two upper chambers (atrial septum).

Lack of blood flow to the right ventricle causes the chamber to develop poorly and become small and ineffective as a pump. The tricuspid valve, which lies between the right upper and lower chambers, may also be poorly developed.

As the right atrium empties its oxygen-poor blood through the hole in the heart wall into the left atrium, the bluish blood mixes with red, oxygen-rich blood in the left upper chamber. The resulting mixture of oxygen-poor and oxygen-rich blood is pumped out of the heart through the aorta and to the body. With less oxygen in the blood circulating through the body, the baby may appear blue (cyanotic).

In newborn babies, some blood leaving the heart via the aorta may go to the lungs through the ductus arteriosus, the blood vessel all babies have before birth. In the mother's womb, this blood vessel carries blood between the aorta and the pulmonary artery. In most babies, this blood vessel begins to close within hours or days of the baby's birth. If the ductus arteriosus closes in a baby with PA/IVS, severe cyanosis will develop because the oxygen-rich blood flowing from the lungs into the circulation is further reduced.

Once the ductus arteriosus begins to close, or if the hole in the wall between the two atria becomes smaller, the baby will become quite ill, and immediate medical attention will be required.

Progression and possible complications

A child with PA/IVS will develop normally before birth, with oxygen-rich blood flowing through the PFO (a hole in the heart wall between the heart’s upper chambers) and the ductus arteriosus. Immediately after birth, the child may also do well. However, after birth, the baby may develop an intense bluish discoloration of the skin.

Abnormalities of the heart (coronary) arteries, including persistent connections from the right ventricle to the coronary arteries (sinusoids) and coronary artery narrowing (stenosis), are sometimes associated with PA/IVS. While this may be suspected from a heart ultrasound, a diagnostic catheterization is often necessary to further define the anatomy before any surgical repair. Heart catheterization is a procedure during which a thin, flexible tube (catheter) is fed through an artery to the heart and used to take pictures. The presence of coronary sinusoids may be a risk factor for sudden death.

Treatment

Initially, babies born with PA/IVS will require a medicine called prostaglandin E1 to keep the ductus arteriosus open. Since the pulmonary valve is closed, the ductus arteriosus must be kept open to allow blood to get to the lungs to pick up oxygen.

Even though the right ventricle may be small initially, it may be possible to use this ventricle to supply blood to the lungs. The tricuspid valve and body of the right ventricle need to be of reasonable size. Also, the coronary arteries can’t be “right ventricle dependent.” In other words, blood flow through the coronary arteries can’t depend on the presence of the abnormal communications from the right ventricle to the coronary circulation, which may have areas of narrowing. If the coronary artery supply is very abnormal, this may be a very high-risk situation regardless of which intervention is performed. In some situations, a baby with these kinds of coronary abnormalities may be referred for heart transplantation.

In certain circumstances, the valve plate may be able to be perforated in the catheterization lab. A balloon dilation catheter may be used to open the valve plate (balloon valvuloplasty). This will allow blood from the right ventricle to pass directly into the lung arteries. For some babies, this may allow enough blood to pass through to the lungs. However, some babies will need additional blood flow to the lungs. If this occurs, surgery will be performed to place a tube from one of the arteries directly to the lungs, which is called a modified Blalock-Taussig shunt. Another option is for a small metal tube called a stent to be placed in the ductus arteriosus to keep it from closing.

As the child grows, the valve area may renarrow, and it may be necessary to undergo another valvuloplasty to open the valve further. Some children will need to undergo another operation to make sure that enough blood gets to the lungs.

If the right ventricle and its components are too small, the child may have to go down a “single ventricle” pathway for treatment. This is a staged surgical route ending up with a Fontan repair.