[2] The right main pulmonary veins (contains oxygenated blood) pass behind the right atrium and superior vena cava; the left in front of the descending thoracic aorta.

[2] The pulmonary veins play an essential role in respiration, by receiving blood that has been oxygenated in the alveoli and returning it to the left atrium.

A groundbreaking study published in 1998 identified the pulmonary vein as the predominant trigger for atrial fibrillation.

[3] Atrial fibrillation frequently results from bursts of tachycardia that originate in muscle bundles extending from the atrium to the pulmonary veins.

[citation needed] This article incorporates text in the public domain from page 642 of the 20th edition of Gray's Anatomy (1918)