Pulmonary veins
Venae pulmonales
There are usually four pulmonary veins, right and left superior and inferior. They are valveless and return oxygenated blood from the lungs to the left atrium.
Overview
The pulmonary veins begin in the alveolar capillary network and run between the bronchopulmonary segments, where they serve as surgical landmarks. They join to form usually two veins from each lung, which enter the back of the left atrium. At the hilum they are the most anterior and inferior structures. The inferior pulmonary vein is the lowest structure in the hilum and lies at the top of the pulmonary ligament. The pattern varies: a common left trunk or a separate right middle lobe vein is quite frequent.
Sleeves of left atrial muscle extend 1–3 cm along each vein. Cells in these sleeves can fire spontaneously and are the main triggers of atrial fibrillation. This is why electrically isolating the pulmonary veins by catheter ablation is the cornerstone of rhythm-control treatment.
In the adult, the pulmonary veins are the only veins that carry well-oxygenated blood (PO₂ ≈100 mmHg). A small admixture of bronchial venous blood slightly lowers the oxygen content of left atrial blood.
- Location
From the lung hila to the posterior wall of the left atrium, within the middle mediastinum. The oblique pericardial sinus lies between them.
Anatomy
- Tributaries
Intersegmental and intrasegmental veins of the lungs, the visceral pleura and some bronchial veins.
Function
- Return oxygenated blood from the lungs to the left heart.
- Act as a reservoir of blood for the left ventricle.
Clinical significance
Pulmonary vein isolation
Catheter ablation encircles the openings of the pulmonary veins with radiofrequency, cryothermal or pulsed-field energy. This electrically isolates the triggers of atrial fibrillation.
Total anomalous pulmonary venous return
In total anomalous pulmonary venous return, all the pulmonary veins drain into the systemic venous system instead of the left atrium. The baby survives only if there is a right-to-left shunt (an ASD or patent foramen ovale), and presents with cyanosis. The supracardiac type gives a "snowman" heart shadow on chest radiograph.
Pulmonary venous hypertension
Left ventricular failure or mitral stenosis raises pressure in the pulmonary veins and capillaries. This causes upper-lobe venous diversion, interstitial oedema and then alveolar oedema.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.