Pulmonary atresia is a congenital heart defect in which the pulmonary valve fails to form properly and completely blocks the passage of blood to the lungs. The pulmonary valve’s primary function is to deliver blood back to the lungs to pick up oxygen. When the valve is so malformed as to not provide any pathway to the smaller pulmonary arteries, heart failure is imminent if not surgically addressed.
Often, pulmonary atresia is accompanied by other defects. A variant of Tetralogy of Fallot often occurs with pulmonary atresia. In other cases, the formation of the pulmonary valve and the right ventricle are both affected. This serious, though rare set of defects, called hypoplastic right heart syndrome, cannot be corrected, but is addressed either through the staged surgeries of the Fontan or through transplantation.
Whether alone or accompanied by other defects, pulmonary atresia must be treated during the first few days of a child’s life. Diagnosis, if not made prenatally, is usually made once the child is born, when the newborn will appear intensely cyanotic or blue. Though all children appear somewhat blue right after delivery, they become pinker as oxygenated blood flows through their system. A child with pulmonary atresia, however, does not become pinker, but may actually become even paler and more cyanotic within a few minutes.
Attending obstetricians or other medical staff will notice cyanosis. If necessary, the baby is transferred to a facility with a pediatric cardiology and surgery department for immediate treatment. More fortunate parents may either have a prenatal diagnosis of pulmonary atresia through ultrasound, or may give birth to their children in a hospital with a cardiology department, so transfer is not necessary. In either case, diagnosis will be confirmed shortly after birth with a fetal echocardiogram, a sonogram of the heart.
Before surgery, the child is often given an intravenous medication, prostaglandin E, which helps keep the patent ductus from closing. This small hole in the atrial septal wall normally closes within a few hours of birth. It creates a passageway for oxygenated and unoxygenated blood to mix, thus allowing some oxygenated blood to get to the body of a child with pulmonary atresia.
Prostaglandin E can only work for a few days before heart failure occurs. The next step for many infants with pulmonary atresia is surgical. Cardiothoracic surgeons perform a Blalock-Taussig (B-T) shunt, which takes the place of the patent ductus. The shunt is a tiny tube that allows for the mixing of blood so that tissues can receive oxygen-rich blood. Even with the shunt, the oxygen saturation levels of an affected infant are frequently somewhere between 80-85%, compared to the normal rate of 96-100%.
Though in most people, a low oxygen rate would be fatal, this is not the case for a child with a B-T shunt. Infants and young children can survive with this reduced oxygenation, though it can affect growth, cause clubbing of the extremities, and lead to eventual heart failure. The B-T shunt is only a first step, however, used to give a child time to grow before attempting repair, when possible. In Tetralogy of Fallot with pulmonary atresia, surgeons may elect to forgo the shunt and repair the defects all at once, including replacing the pulmonary valve with a porcine, bovine or donor valve. It is considered standard to replace the pulmonary valve every eight to ten years, as the child will outgrow the valve.
In hypoplastic right heart with pulmonary atresia, the Fontan procedure is performed in several staged operations during the first few years of life. In the final stage, the malformed pulmonary valve is simply removed and the stump sewn down into the heart. To prevent blood clots, children who have had either valve replacement or the Fontan must take daily low dose aspirin.
When pulmonary atresia presents by itself, surgeons perform a valve replacement. However, pulmonary atresia by itself is quite rare. Valve replacements must be monitored and replaced as the child grows.
Once surgical repair is complete, the child requires yearly monitoring of the heart. However, even with the presence of hypoplastic right heart, surgical techniques provide the child with a good outcome, though transplant is necessary 15-30 years post-Fontan. For the child with uncomplicated pulmonary atresia, outlook is excellent, though future surgeries will be required to replace outgrown valves.
