Pulmonary Veins: Anatomy, Function, Variations and Care
Updated: 3 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026
Quick Answer: What are the pulmonary veins?
Pulmonary veins are blood vessels that return oxygen-rich blood from the lungs to the left atrium of the heart. They travel toward the heart like other veins, but they are unique because they carry oxygen-rich rather than oxygen-poor blood. Most people (60%–70%) have four; others have three or five. [1]
Core idea | Plain-language meaning |
Blood carried | Oxygen-rich blood. |
Direction | From the lungs toward the heart. |
Destination | The left atrium. |
Typical number | Four in 60%–70% of people; three or five in others. |
Key role | Return freshly oxygenated blood for the heart to pump to the body. |
Important variations | Some are harmless; some congenital connections interfere with heart function. |
Common tests | Chest X-ray, echocardiography, MRI and CT scan. |
What the research says
Variations in pulmonary vein anatomy are common. A cardiac CT study of 1,420 people (710 with atrial fibrillation and 710 matched controls) found pulmonary vein variants in 28.5% of those with atrial fibrillation and 29.0% of controls (p = 0.8153). The authors concluded that knowing these variants gives an anatomical road map before catheter ablation (Chen et al., Eur Radiol, 2017). [2]
A common left ostium was more frequent in one atrial fibrillation study. In a case-control CT study of 166 patients scheduled for atrial fibrillation ablation and age- and sex-matched controls, a left common ostium was found in 33.7% of patients versus 19.9% of controls (P = 0.004; odds ratio 2.1). Findings on whether particular variants raise atrial fibrillation risk are not consistent across studies (Bittner et al., Europace, 2011). [3]
Pulmonary vein isolation works well early, but success declines over time. A systematic review and meta-analysis of 13 studies (1,774 patients with paroxysmal atrial fibrillation) found pooled success after a single ablation procedure of 78% at 12 months and 59% at 62 months (Kis et al., Curr Cardiol Rev, 2017). [4]
What are the pulmonary veins?
Pulmonary veins are blood vessels that carry oxygen-rich blood from the lungs to the heart. They form part of the pulmonary circuit, which moves blood between the heart and lungs. [1]
Their direction of travel follows the general rule for veins: they carry blood toward the heart. Their blood type is the unusual part. Pulmonary veins are the only veins in the body that carry oxygen-rich blood. [1]
How are pulmonary veins different from pulmonary arteries?
Pulmonary veins and pulmonary arteries differ in both blood type and direction.
Vessel | Blood carried | Direction of travel |
Pulmonary veins | Oxygen-rich blood. | From the lungs to the heart. |
Pulmonary arteries | Oxygen-poor blood. | From the heart to the lungs. |
This is why the pulmonary circuit is an exception to the usual pattern. Veins still carry blood toward the heart, and arteries still carry blood away from the heart, but the oxygen content is reversed.
What do the pulmonary veins do?
Pulmonary veins collect oxygen-rich blood from the lungs and carry it to the heart. From the left atrium, blood moves to the left ventricle and then out through the aorta to the body's organs and tissues. [1]
Their role is essential because the heart needs freshly oxygenated blood to pump to the rest of the body.
Step | What happens |
1. Lung gas exchange | Blood becomes oxygen-rich in the lungs. |
2. Pulmonary veins | Collect and carry oxygen-rich blood toward the heart. |
3. Left atrium | Receives the blood through the pulmonary-vein openings. |
4. Left ventricle | Receives blood from the left atrium. |
5. Aorta | Carries blood from the left ventricle to the body. |
Where are the pulmonary veins located?
Pulmonary veins are located between the lungs and the heart. Smaller vessels converge in each lung to form a pair of pulmonary veins. Each pair leaves its lung through the hilum, also called the root, and travels to the heart. [1]
The veins connect with the left atrium, the top-left chamber of the heart. Normally, each vein connects directly to the left atrium through one of four openings, or ostia. [1]
How many pulmonary veins are there?
Most people, or about 60% to 70%, have four pulmonary veins. Other people have three or five. Differences in the number of veins do not cause health problems and are simply anatomical variations some people are born with. [1]
The usual four are a right superior, right inferior, left superior and left inferior pulmonary vein. "Superior" means above, and "inferior" means below. [1]
Pulmonary vein | Drainage area |
Right superior | Upper and middle lobes of the right lung. |
Right inferior | Lower lobe of the right lung. |
Left superior | Upper lobe of the left lung and the lingula. |
Left inferior | Lower lobe of the left lung. |
What harmless anatomical variations can occur?
About 38% of people have harmless variations in pulmonary-vein structure. These can affect the number of veins or how they connect with the left atrium while still allowing oxygen-rich blood to enter the heart normally. [1]
A common left-sided trunk occurs when the two left pulmonary veins merge into a shared trunk before reaching the left atrium. They then drain through one opening instead of two. A short left-sided trunk is the most common variation overall and affects about 15% of people. [1]
An accessory right pulmonary vein is an extra right pulmonary vein that drains separately into the left atrium. Instead of two right pulmonary veins, a person has three. [1]
These variations are considered healthy when they still allow oxygen-rich blood to reach the left atrium and continue through the normal circulation.
Which congenital variations can interfere with heart function?
Some congenital variations prevent pulmonary veins from draining properly into the left atrium. These can interfere with normal heart function and are among the congenital heart defects.
Total anomalous pulmonary venous return
Total anomalous pulmonary venous return, or TAPVR, means that none of the pulmonary veins connects with the left atrium. Instead, the veins connect with the right atrium directly or through other veins. Oxygen-rich blood that should enter the left side mixes with oxygen-poor blood on the right side. [1]
TAPVR is a form of cyanotic heart disease that needs surgery. It is usually diagnosed soon after birth, although diagnosis can occur in adulthood. In the U.S., about 1 in 7,809 babies are diagnosed with TAPVR. [1]
Partial anomalous pulmonary venous return
Partial anomalous pulmonary venous return, or PAPVR, means that at least one pulmonary vein connects with the left atrium. Some oxygen-rich blood can therefore pass through the aorta to the body, and the condition is usually less critical than TAPVR, although treatment may still be needed. [1]
Estimates suggest PAPVR may affect 1 in 143 people and that it can occasionally go unnoticed until adulthood. [1]
Babies with TAPVR or PAPVR usually have an atrial septal defect. The opening can allow blood to travel from the right atrium to the left atrium and then out to the body until treatment, although the blood contains less oxygen than it should. [1]
How large are the pulmonary veins?
The diameter of a healthy pulmonary vein ranges from 9 to 13 millimeters. Diameter varies along the route from the lungs to the heart, and veins generally become wider as they approach the heart. [1]
The left inferior pulmonary vein is an exception: it starts wider as it leaves the left lung and becomes narrower as it approaches the heart. [1]
These measurements describe typical anatomy. They are not personal diagnostic cutoffs.
What are pulmonary veins made of?
Pulmonary veins have the three tissue layers found in veins generally.
Layer | Role |
Tunica adventitia | Outer layer that gives the vein structure and shape. |
Tunica media | Middle layer with smooth muscle cells that allow widening or narrowing. |
Tunica intima | Inner layer lined with smooth endothelial cells that lets blood flow easily. |
Pulmonary veins also differ from other veins because a thin myocardial layer partly covers them near the left atrium. This sleeve of heart muscle has an average length of 9 millimeters, and superior pulmonary veins have longer sleeves than inferior veins. [1]
What conditions can affect the pulmonary veins?
The pulmonary veins can be affected by several conditions, including pulmonary-vein stenosis.
Condition | Description |
PAPVR | One or more pulmonary veins are not connected normally to the left atrium; usually diagnosed in babies but sometimes in adults. |
Pulmonary-vein obstruction | A blockage in a vein, often caused by a tumor in the heart or lungs extending into it. |
Pulmonary-vein stenosis | Narrowing of one or more veins; causes differ by age and context. |
Pulmonary-vein thrombosis | A blood clot in a vein; typically occurs in people with lung cancer or after a lung transplant. |
Pulmonary venous hypertension | Raised blood pressure in the pulmonary veins, usually caused by left-sided heart failure; other causes include cardiac tumors and mitral-valve stenosis. |
TAPVR | None of the pulmonary veins connects to the left atrium; usually diagnosed soon after birth. |
In babies, pulmonary-vein stenosis is often caused by congenital heart defects that affect blood flow. In adults, it can sometimes occur as a complication of catheter radiofrequency ablation used to treat atrial fibrillation. [1]
Related guides on Rinnit: pulmonary hypertension, pulmonary embolism, heart failure and the mitral valve.
What role do pulmonary veins play in atrial fibrillation?
Atrial fibrillation, or A-Fib, is an abnormal heart rhythm that often begins in the pulmonary veins or at their junction with the left atrium. Any pulmonary vein may trigger A-Fib, but the left superior pulmonary vein is most often involved. [1]
Healthcare providers use a catheter-based procedure called pulmonary-vein isolation to treat A-Fib. This article does not provide procedural instructions or determine whether a treatment is appropriate for an individual. [1]
What tests check the pulmonary veins?
Providers use several imaging tests to check the pulmonary veins.
Test | Role in this context |
Chest X-ray | One of the imaging tests providers may use. |
Echocardiography | One of the imaging tests providers may use. |
MRI | One of the imaging tests providers may use. |
CT scan | One of the imaging tests providers may use. |
The right test depends on the suspected condition and a person's clinical context. An imaging test should be ordered and interpreted by a qualified professional.
How should a diagnosed pulmonary-vein condition be managed?
If you have been diagnosed with a pulmonary-vein condition, follow your healthcare provider's guidance. Many pulmonary-vein problems arise from other medical conditions that need careful treatment and monitoring.
Ask a qualified professional what you can do at home to manage the condition and reduce symptoms. Do not change prescribed treatment or interpret an imaging result from this article.
When should you seek professional assessment?
Seek professional assessment for new or concerning breathing, circulation or heart-rhythm symptoms, especially when a heart or lung condition is already known. This guide cannot determine whether symptoms involve a pulmonary vein.
Call 911 or go to the emergency room for severe or sudden shortness of breath, chest discomfort, fainting, coughing up blood, bluish lips or skin, a very fast or irregular heartbeat with dizziness, or rapidly worsening symptoms.
Conclusion: Pulmonary veins return oxygen-rich blood
Pulmonary veins carry oxygen-rich blood from the lungs to the left atrium. Most people have four, but three or five can also be healthy anatomical variations. [1]
Their unusual feature is that they are veins carrying oxygen-rich blood. Their direction is familiar: they travel toward the heart. Together with the pulmonary arteries, they form the pulmonary circuit that links lung gas exchange with heart function. [1]
Some structural variations are harmless, while anomalous connections, obstruction, stenosis, thrombosis, pulmonary venous hypertension and atrial-fibrillation triggers can require professional evaluation and care. Chest X-ray, echocardiography, MRI and CT scan are among the tests used to check them. [1]
Use this guide to prepare questions for a qualified healthcare professional. Understanding pulmonary-vein anatomy is a starting point for informed care—not a diagnosis. [1]
Frequently Asked Questions
What are pulmonary veins?
Pulmonary veins are blood vessels that carry oxygen-rich blood from the lungs to the heart, specifically the left atrium.
Do pulmonary veins carry oxygen-rich or oxygen-poor blood?
Pulmonary veins carry oxygen-rich blood. They are the only veins in the body that carry oxygen-rich blood.
Where do pulmonary veins carry blood?
Pulmonary veins carry blood from the lungs to the left atrium of the heart.
How many pulmonary veins does a person have?
Most people have four. About 60% to 70% have four, while others have three or five. The difference is usually a harmless anatomical variation.
What are the four common pulmonary veins?
The four common pulmonary veins are the right superior, right inferior, left superior and left inferior pulmonary veins.
How are pulmonary veins different from pulmonary arteries?
Pulmonary veins carry oxygen-rich blood from the lungs to the heart. Pulmonary arteries carry oxygen-poor blood from the heart to the lungs.
Where do pulmonary veins enter the heart?
Pulmonary veins normally connect directly with the left atrium through four openings, one for each vein.
What is a common left-sided trunk?
A common left-sided trunk is a harmless variation in which the two left pulmonary veins merge before reaching the left atrium and drain through one opening.
What is TAPVR?
Total anomalous pulmonary venous return is a congenital condition in which none of the pulmonary veins connects with the left atrium. It is a form of cyanotic heart disease that needs surgery.
What is PAPVR?
Partial anomalous pulmonary venous return means that at least one pulmonary vein connects with the left atrium, while another does not. It may need treatment but is usually less critical than TAPVR.
What is pulmonary-vein stenosis?
Pulmonary-vein stenosis is narrowing of one or more pulmonary veins. Causes can differ in babies and adults.
What is pulmonary-vein thrombosis?
Pulmonary-vein thrombosis is a blood clot in a pulmonary vein. It typically occurs in people with lung cancer or after a lung transplant.
What is pulmonary venous hypertension?
Pulmonary venous hypertension is raised blood pressure in the pulmonary veins. It is usually caused by left-sided heart failure; other causes include cardiac tumors and mitral-valve stenosis.
How are pulmonary veins involved in atrial fibrillation?
Atrial fibrillation can begin in the pulmonary veins or where they meet the left atrium. The left superior pulmonary vein is most often involved.
What is pulmonary-vein isolation?
Pulmonary-vein isolation is a catheter-based procedure healthcare providers use to treat atrial fibrillation.
How are pulmonary veins checked?
Imaging tests include chest X-ray, echocardiography, MRI and CT scan.
How large are healthy pulmonary veins?
A healthy pulmonary vein measures 9 to 13 millimeters in diameter. This is an anatomical reference, not a personal diagnostic cutoff.
What are pulmonary veins made of?
Pulmonary veins have tunica adventitia, tunica media and tunica intima. Pulmonary veins are also partly covered by a thin sleeve of heart muscle near the left atrium.
What is the pulmonary circuit?
The pulmonary circuit is the network of blood vessels that moves blood between the heart and lungs. It includes the pulmonary veins and pulmonary arteries.
What does "superior" mean in a pulmonary-vein name?
"Superior" means above. "Inferior" means below.
What is the hilum of the lung?
The hilum of the lung is the spot where each pair of pulmonary veins leaves its lung. It is also called the root of the lung.
What is an accessory right pulmonary vein?
An accessory right pulmonary vein is an extra right pulmonary vein that drains separately into the left atrium.
When should I seek care for a possible pulmonary-vein problem?
Seek professional assessment for new or concerning breathing, chest, circulation or heart-rhythm symptoms. Severe or sudden shortness of breath, chest discomfort, fainting, coughing up blood, bluish lips or skin, rapid or irregular heartbeat or rapidly worsening symptoms need emergency care: call 911.
How should a diagnosed pulmonary-vein condition be managed?
Follow professional guidance. Many pulmonary-vein conditions stem from other medical problems requiring careful treatment and monitoring.
Related Reading
Pulmonary Vein Isolation (PVI): Ablation for Atrial Fibrillation explains pulmonary vein isolation.
References
Cleveland Clinic. Pulmonary Veins: Anatomy and Function. Cleveland Clinic. Updated June 17, 2022. https://my.clevelandclinic.org/health/body/23242-pulmonary-veins
Chen J, Yang ZG, Xu HY, et al. Assessments of pulmonary vein and left atrial anatomical variants in atrial fibrillation patients for catheter ablation with cardiac CT. Eur Radiol. 2017;27(2):660-670. PMID 27229337. https://doi.org/10.1007/s00330-016-4411-6
Bittner A, Mönnig G, Vagt AJ, et al. Pulmonary vein variants predispose to atrial fibrillation: a case-control study using multislice contrast-enhanced computed tomography. Europace. 2011;13(10):1394-1400. PMID 21593040. https://doi.org/10.1093/europace/eur145
Kis Z, Muka T, Franco OH, et al. The Short and Long-Term Efficacy of Pulmonary Vein Isolation as a Sole Treatment Strategy for Paroxysmal Atrial Fibrillation: A Systematic Review and Meta-Analysis. Curr Cardiol Rev. 2017;13(3):199-208. PMID 28124593. https://doi.org/10.2174/1573403X13666170117125124
Disclaimer
This article is for general educational purposes and is not a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare professional with any questions about a medical condition or treatment.
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