Definition of Absent pulmonary valve:

Absent pulmonary valve is a rare defect in which the pulmonary valve that carries oxygen-poor blood from the heart to the lungs is either missing or poorly formed. This condition is present at birth (congenital).

See also: Tetralogy of Fallot

Causes, incidence, and risk factors:

Absent pulmonary valve occurs when the pulmonary valve doesn' t form or develop properly while the baby is in the mother' s womb. It often occurs as part of a rare condition called tetralogy of Fallot.

When the pulmonary valve is missing or does not work well, not enough blood can flow to the lungs to get oxygen.

There is also usually a hole between the left and right ventricles of the heart (ventricular septal defect). This defect will also lead to low-oxygen blood being pumped out to the body.

The skin will have a blue appearance (cyanosis), because the body's blood contains a low amount of oxygen.

Absent pulmonary valve also results in very enlarged (dilated) branch pulmonary arteries (the arteries that carry blood to the lungs). They can become so enlarged that they press on the tubes that bring air to the lungs (bronchi) and cause breathing problems.

Other heart defects that can occur with absent pulmonary valve include:

• Abnormal tricuspid valve
• Atrial septal defect
• Double outlet right ventricle
• Ductus arteriosis
• Endocardial cushion defect
• Marfans syndrome
• Tricuspid atresia

Heart problems that occur with absent pulmonary valve may be due to defects of the genes (chromosomes).