The pulmonary vein is unique in that it is the only vein that carries oxygenated blood.
Until delivery, fetal blood flow bypasses these vessels, which open at birth upon exposure to oxygen.
Medical conditions may occur in adults as well, such as pulmonary venous hypertension.
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Anatomy
The pulmonary veins along with the pulmonary arteries make up the pulmonary circulation.
They are made up of three layers of smooth muscle tissue called tunics.
From the capillaries, blood enters the bronchial veins, which then drain into the pulmonary veins.
The left pulmonary veins pass in front of the descending aorta to enter the left atrium.
Anatomic Variations
People often have four pulmonary veins, but variations occur in 38 percent of people.
In some cases, there will be five and other times only three pulmonary veins.
The two left pulmonary veins often fuse, leading to a total of three pulmonary veins.
These vessels may also be affected by conditions in the region of the heart where they empty.
Hypoplasia of the Pulmonary Veins
In some children, the pulmonary veins fail to develop completely (hypoplasia).
This is usually associated with hypoplastic left heart syndrome.
It is an uncommon but serious birth defect and is often combined with other heart abnormalities.
There are several degrees of this condition of varying concern.
In this condition, oxygenated blood from the lungs mixes with deoxygenated blood in the right atrium.
Some congenital heart conditions run in families, but this does not appear to be a significant risk factor.
This condition, along with several types of congenital heart disease, can often be diagnosed with an echocardiogram.
If the opening is large enough, it may be asymptomatic.
However, if the opening is small and restrictive, it can be surgically repaired.
Pulmonary Arteriovenous Malformation
This is a condition in which there is communication between the pulmonary artery and pulmonary vein.
It may be asymptomatic or cause shortness of breath.
When narrowed, angioplasty may be done or stents placed to maintain the caliber of the vein.
Pulmonary vein stenosis sometimes occurs after ablation for atrial fibrillation.
Pulmonary Vein Obstruction
The pulmonary veins may become obstructed in a few conditions such as lung cancer or tuberculosis.
Worsening shortness of breath in someone with lung cancer can be a sign of this complication.
Surgical and Procedural Damage
The pulmonary veins may also be damaged during surgical procedures.
This includes the different types of surgery for lung cancer.
Radiofrequency ablation for arrhythmias may also result in damage.
Pulmonary Venous Hypertension
Pulmonary hypertension is a condition in which the pressure in the pulmonary veins is elevated.
Symptoms can include shortness of breath, swelling of the legs, and fatigue.
It is diagnosed with a right heart angiogram, which finds an increase in capillary wedge pressure.
The primary treatment is to address the underlying cause of the disease.
When it does occur, it is often related to a malignancy such aslung cancer.
Role in Atrial Fibrillation
The science connecting the pulmonary veins with atrial fibrillation is relatively new.
Pulmonary vein isolation is a procedure that is sometimes done to treat atrial fibrillation.
A complication that sometimes occurs with this procedure is pulmonary venous stenosis, which is discussed above.
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