Pulmonary atresia

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**Pulmonary atresia**
*Classification & external resources*
ICD-10	Q 25.5
ICD-9	747.3
MedlinePlus	001091
eMedicine	ped/2526 ped/2898
MeSH	C14.240.670

Pulmonary atresia is a congenital malformation of the pulmonary valve in which the valve orifice fails to develop. The valve is completely closed thereby obstructing the outflow of blood from the heart to the lungs. The pulmonary valve is located on the right side of the heart between the right ventricle and pulmonary artery. In a normal functioning heart, the opening to the pulmonary valve has three flaps that open and close like one way doors. As these flaps open and close they force blood to flow forward into the pulmonary artery and backward into the right ventricle then forward again to the lungs where the blood becomes oxygenated. With the disease pulmonary atresia, the flap-like openings are completely covered by a layer of tissue, thus preventing the ability of blood flow to the lungs to become oxygenated. The body requires oxygenated blood for survival. Pulmonary atresia is not threatening to a developing fetus however, because the mother's placenta provides the needed oxygen since the baby's lungs are not yet functional. Once the baby is born its lungs must now provide the oxygen needed for survival, but with Pulmonary atresia there is no opening on the pulmonary valve for blood to get to the lungs and become oxygenated. Due to this, the newborn baby is blue in color and pulmonary atresia can usually be diagnosed within hours or minutes after birth.

There are two types of pulmonary atresia. The first type is called Pulmonary atresia with intact ventricular septum (PA-IVS). PA-IVS is a rare congenital lesion. This lesion can be diagnosed during the fetal stage of life by using fetal echocardiography, which is a test that uses sound waves to look at the structure of an unborn baby's heart. PA-IVS involves complete blockage of the pulmonary valve located on the right side of the heart. This blockage thus prevents the flow of blood to the lungs. Because of this lack of blood flowing through the right side of the heart, the structures on that side, such as the pulmonary valve and the tricuspid valve, are abnormally small. The genetic cause of PA-IVS is unknown. It is rare, occuring in around 7.1-8.1 per every 100,000 live births. The second type of pulmonary atresia is called Pulmonary atresia with ventricular septal defect or VSD. PA-VSD is identified by underdevelopment of the right ventricle. It is a second opening in the ventricular wall. This opening provides a way out for blood in the right ventricle. When this second opening (VSD) does not exist, very little blood goes to the right ventricle, which is what causes it to be underdeveloped. This defect can also be determined before birth. Out of all congenital cardiac malformations, it is estimated that PA-VSD occurs in 2.5-3.4% of the cases. The genetic cause of PA-VSD is not known; it is found however, that children whose parents have PA-VSD are at a higher risk for congenital heart lesions.

[edit] Prognosis

Babies with this type of cyanotic congenital heart disease survive only for the first few days of life while the normal fetal shunts between left and right circulations remain patent.

Without an operation in that period to open the pulmonary valve or to make a shunt between the aorta and the pulmonary arteries, the condition is fatal.

Many children with Pulmonary Atresia will go on to lead 'normal' lives.

[edit] Treatment

The type of surgery recommended depends on the size of the right ventricle and the pulmonary artery.

If they are normal in size and the right ventricle is able to pump blood, open heart surgery can be performed to make blood flow through the heart in a normal pattern.

If the right ventricle is small and unable to act as a pump, doctors may perform operations called the Fontan procedure. In this two-stage procedure, the right atrium is disconnected from the pulmonary circulation. The systemic venous return goes directly to the lungs, by-passing the heart.