Partial anomalous pulmonary venous return, commonly abbreviated PAPVR, is a congenital heart anomaly in which one or more pulmonary veins connect to the wrong chamber of the heart, delivering oxygen-rich blood back to the right side instead of the left atrium where it belongs. Though present from birth, PAPVR often produces no symptoms for decades and is frequently discovered by accident on a chest CT ordered for something else entirely. How much trouble it causes depends largely on how many veins are misrouted and whether other heart defects ride along with it.
What Goes Wrong in PAPVR
Normally, four pulmonary veins carry freshly oxygenated blood from the lungs into the left atrium, where it is pumped out to the body. In PAPVR, at least one of those veins takes a wrong turn and empties into the right atrium, the superior vena cava, or another vein on the right side of the circulation. The remaining veins still drain normally into the left atrium, which distinguishes PAPVR from the more severe total anomalous pulmonary venous connection (TAPVC), where all four veins are misrouted.1PubMed Central. Partial anomalous pulmonary venous connection: state-of-the-art review with assessment using a multidetector computed tomography angiography The result is a left-to-right shunt: some blood that should head out to the body loops back through the lungs instead, forcing the right side of the heart to handle extra volume.
The anomaly arises from a misstep early in fetal development, when the primitive venous plexus surrounding the lung buds is supposed to lose its connections to the systemic veins and reroute entirely to the left atrium. When that remodeling is incomplete, one or more veins retain their original systemic connection. This can happen on either side of the chest, and the specific drainage site varies. One large CT-based study found PAPVR in roughly 0.1% of adult chest scans, with the left upper lobe involved about 47% of the time, the right upper lobe in 38%, and the right lower lobe in 13%.2Journal of Thoracic Imaging. MDCT of Partial Anomalous Pulmonary Venous Return (PAPVR) in Adults
How It Affects the Heart Over Time
When only a single small vein is misrouted, the extra blood flowing through the right heart may be trivial. The shunt fraction, expressed as the ratio of blood flow through the lungs compared to the body (Qp/Qs), stays close to 1.0, and the heart barely notices. But when multiple veins are involved or when an atrial septal defect (ASD) accompanies the anomaly, the shunt grows larger and the right heart has to work harder. Research in adults with PAPVR has shown a strong correlation between the shunt ratio and the size of the right ventricle and right atrium: the bigger the shunt, the more the right heart dilates.3International Journal of Cardiology Congenital Heart Disease. Partial anomalous pulmonary venous return in adults: Insight into pulmonary hypertension Patients who also had an ASD had notably larger shunts and more right-heart enlargement than those with PAPVR alone.
Over years, the chronic volume overload can gradually raise pressures in the pulmonary arteries. This slow-developing pulmonary hypertension is one of the main long-term risks, and it can eventually lead to right-sided heart failure if the condition is never addressed.4PubMed Central. Pulmonary Hypertension Secondary to Partial Anomalous Pulmonary Venous Return in an Elderly Atrial arrhythmias such as atrial fibrillation or flutter are another complication that can emerge in middle age or later, driven by the chronically stretched right atrium.
Why PAPVR Hides in Plain Sight
The classic story of PAPVR is late discovery. Many people carry it through childhood and early adulthood with no symptoms at all, because the shunt is small enough that the heart compensates easily. A person might first notice exercise intolerance, unexplained shortness of breath, or recurrent lung infections in their 40s or 50s. One case report describes a 58-year-old woman whose progressive breathlessness was initially blamed on obstructive lung disease and classified as a form of pulmonary hypertension. It took two more years before imaging revealed that an anomalous left pulmonary vein draining into the innominate vein was the real culprit.5PubMed Central. Delayed Diagnosis of Partial Anomalous Pulmonary Venous Return in an Adult With Pulmonary Hypertension
Misdiagnosis is disturbingly common because the symptoms overlap with everyday conditions like asthma, deconditioning, and chronic obstructive pulmonary disease. Clinicians have flagged the importance of considering PAPVR in anyone with unexplained exertional breathlessness, even when the presentation looks like something mundane.6CHEST. Cardiovascular Disease Case Report Posters The same goes for sinus venosus ASDs, which are strongly associated with right upper lobe PAPVR and can be missed on standard echocardiography, leaving the underlying shunt undetected.7PubMed Central. Sinus Venosus Atrial Septal Defect as an Overlooked Source of Shortness of Breath Among Patients With Pulmonary Arterial Hypertension
The Sinus Venosus ASD Connection
Among the heart defects that tag along with PAPVR, sinus venosus ASDs deserve special attention. Unlike the more common secundum ASD that sits in the center of the atrial septum, a sinus venosus defect is located high up near the junction of the superior vena cava and the right atrium. It almost always comes packaged with anomalous drainage of the right upper lobe pulmonary vein. In the CT-based study mentioned earlier, 42% of right upper lobe PAPVR cases had an associated sinus venosus ASD.8Journal of Thoracic Imaging. MDCT of Partial Anomalous Pulmonary Venous Return (PAPVR) in Adults The combination creates a larger shunt than PAPVR alone would, because blood passes both through the anomalous vein and through the hole in the septum.
Because the defect sits so high, standard transthoracic echocardiography frequently misses it. The sound beam simply does not image that part of the septum well. This is one of the main reasons PAPVR with sinus venosus ASD can elude detection for decades even in people who have had cardiac ultrasounds.
Scimitar Syndrome
Scimitar syndrome is a distinctive variant of PAPVR in which the right pulmonary vein drains into the inferior vena cava rather than the left atrium. The name comes from the curved shadow the anomalous vein casts on a chest X-ray, resembling a Turkish scimitar sword. Beyond the abnormal vein, scimitar syndrome often includes an underdeveloped right lung, abnormal arterial blood supply to the right lung from the aorta, and sometimes an ASD.9PubMed Central. Partial Anomalous Pulmonary Venous Return: Scimitar Vein Adults with scimitar syndrome tend to present with breathlessness and recurrent lung infections, and any pulmonary hypertension that develops is usually mild.
Scimitar syndrome accounted for about 13% of PAPVR cases in one large imaging series.10Journal of Thoracic Imaging. MDCT of Partial Anomalous Pulmonary Venous Return (PAPVR) in Adults It is sometimes picked up incidentally when a characteristic vascular shadow appears on a routine chest X-ray, which makes it one of the more recognizable forms of PAPVR on conventional imaging.
PAPVR and Turner Syndrome
One population in which PAPVR shows up at strikingly high rates is people with Turner syndrome, a chromosomal condition affecting roughly 1 in 2,000 to 2,500 females. While PAPVR occurs in about 0.1% of the general population on CT screening, studies using advanced cardiac imaging in Turner syndrome patients have found the anomaly in roughly one out of four. One study of 96 Turner syndrome patients diagnosed PAPVR in 25% of them, and more than half of those cases had never been identified before.11PubMed. Partial anomalous pulmonary venous return in Turner syndrome Nearly half of the affected patients already showed right-sided heart enlargement. A separate screening study using 4D flow cardiac MRI found PAPVR in 12% of 73 Turner syndrome patients, with those affected showing meaningfully larger right ventricles and higher shunt fractions.12PubMed Central. Use of 4D Flow Cardiac Magnetic Resonance Imaging to Screen for Partial Anomalous Pulmonary Venous Return in Patients with Turner Syndrome
The variation in reported prevalence (12% to 25%) likely reflects differences in imaging technique and how aggressively clinicians look for the anomaly. The takeaway for anyone managing Turner syndrome is that PAPVR should be actively screened for, not assumed absent. The European Journal of Radiology study explicitly recommended that evaluation of pulmonary venous return be included in the standard cardiac imaging protocol for all Turner syndrome patients.13PubMed. Partial anomalous pulmonary venous return in Turner syndrome
How PAPVR Is Diagnosed
Echocardiography (cardiac ultrasound) is the first-line tool for most heart conditions, and it can detect PAPVR with high sensitivity when the examiner is experienced and looking for it. One large single-center review reported 97.6% sensitivity for anomalous pulmonary venous connections overall.14PubMed Central. Echocardiographic diagnosis of anomalous pulmonary venous connections Experience of 84 cases from 1 medical center But those numbers come from a center that was specifically evaluating for the condition. In routine clinical practice, the miss rate is considerably higher. An older but instructive study found that echocardiography missed the diagnosis in a third of confirmed PAPVR cases, with the detection rate improving dramatically when color flow mapping was used.15PubMed. Echocardiographic evaluation of partial anomalous pulmonary venous drainage Transesophageal echocardiography, where the probe goes into the esophagus behind the heart, performs much better for the sinus venosus region and accurately identified the drainage site in every patient it was used on in that study.
Cross-sectional imaging with CT or cardiac MRI has become the reference standard for mapping PAPVR anatomy before any intervention. CT provides excellent spatial resolution and fast scan times, making it ideal for defining exactly where each anomalous vein connects.16PubMed Central. Multidetector Computed Tomography (MDCT) Angiography Evaluation of Total Anomalous Pulmonary Venous Connection Cardiac MRI adds functional data that CT cannot match: it can quantify right ventricular volumes, measure the shunt fraction with flow analysis, and do all of this without radiation exposure.17PubMed. MR imaging and CT evaluation of congenital pulmonary vein abnormalities in neonates and infants For that reason, MRI is often preferred when the goal is to decide whether a patient’s shunt is large enough to warrant repair, since it directly measures the parameters that guide that decision.
When Repair Is Recommended
Not everyone with PAPVR needs surgery. The decision hinges on symptoms, the size of the shunt, and whether the right heart is showing signs of strain. The general consensus is that repair makes sense when the Qp/Qs ratio is around 1.5 or above, symptoms like exercise intolerance or breathlessness are present, and imaging shows meaningful right-heart enlargement. A case report of a 65-year-old woman with isolated PAPVR illustrates the point: she met criteria for surgery because she was symptomatic and had a high shunt ratio, and after repair she remained free of breathlessness, arrhythmia, and blood clot complications.18PubMed Central. Surgical repair of partial anomalous pulmonary venous return with intact atrial septum in a 65-year-old woman: a case report
Encouragingly, recent data suggest that adults with unrepaired PAPVR and an intact atrial septum who do not meet criteria for surgery tend to stay stable over time. A study following 80 such patients found no temporal deterioration in functional status, cardiac biomarkers, or right-heart measurements at three- and five-year follow-up.19PubMed Central. Outcomes of Adults With Unrepaired Partial Anomalous Pulmonary Venous Return and Intact Atrial Septum That is reassuring for the many people who learn about their PAPVR incidentally and wonder whether they face inevitable decline. For those with small shunts and no symptoms, careful monitoring with periodic imaging may be all that is needed.
The clinical predictors that tilt the scales toward repair include the number of anomalous veins, the volume of the right atrium, and the size of the right ventricle at rest. A risk score incorporating these factors was associated with the decision to operate in the same study, providing clinicians with a structured way to assess who is likely to benefit.20Journal of the American Heart Association. Outcomes of Adults With Unrepaired Partial Anomalous Pulmonary Venous Return and Intact Atrial Septum
Surgical and Catheter-Based Repair Options
When repair is warranted, the traditional approach is open-heart surgery. For PAPVR involving the right upper lobe pulmonary vein draining into the superior vena cava, the Warden procedure is one of the most widely used techniques. It involves cutting the superior vena cava above where the anomalous vein enters, reconnecting it to the right atrial appendage, and creating a baffle that redirects the pulmonary venous blood through the existing or surgically created ASD into the left atrium.21PubMed Central. Adult Partial Anomalous Pulmonary Venous Return Repair and Superior Vena Cava Syndrome: A Delayed Complication of the Warden Procedure This reroutes the blood correctly while keeping the superior vena cava functional.
The Warden procedure generally works well, but it carries specific risks. One outcomes study found that about 12% of patients required reoperation or reintervention within five years for stenosis of the systemic or pulmonary venous pathways. The risk was concentrated in very young and small patients, particularly those under two years old and under seven kilograms, who underwent direct reimplantation of the superior vena cava without any augmentation.22European Journal of Cardio-Thoracic Surgery. Partial anomalous pulmonary venous connection to the superior vena cava: the outcome after the Warden procedure Adults undergoing the same procedure generally fare better, though late superior vena cava syndrome has been reported as a delayed complication.
A newer alternative is transcatheter closure, which avoids open-heart surgery entirely. Introduced in 2014 for patients with sinus venosus defects and associated PAPVR, percutaneous repair uses a covered stent placed in the superior vena cava to wall off the defect and redirect pulmonary venous blood to the left atrium.23PubMed. Transcatheter Closure of Superior Sinus Venosus Defects Worldwide experience is still limited, but in carefully selected patients the approach has been safe and effective. One notable case used 3D-printed heart models and image fusion to guide stent placement in a 63-year-old man with cirrhosis and liver cancer who was too high-risk for conventional surgery, achieving successful exclusion of the defect and unobstructed pulmonary venous return.24PubMed Central. Transcatheter closure of a sinus venosus atrial septal defect using 3D printing and image fusion guidance As experience grows and devices improve, catheter-based approaches will likely become an option for a broader range of patients.
PAPVR During Pregnancy
Pregnancy increases cardiac output by roughly 30 to 50 percent, and for someone with PAPVR that extra volume amplifies the existing left-to-right shunt. The combination of higher blood volume, reduced peripheral resistance, and the procoagulant state of pregnancy can unmask previously silent PAPVR or worsen symptoms in someone who was already mildly affected.25Revista Portuguesa de Cardiologia. Anomalous pulmonary venous return in a pregnant woman identified by cardiac magnetic resonance In some cases, PAPVR is first diagnosed during pregnancy precisely because the hemodynamic stress brings out symptoms for the first time.
For someone with known PAPVR who is planning pregnancy, a pre-conception cardiac assessment including MRI-based shunt quantification is reasonable. If the shunt is large enough to warrant repair, doing so before pregnancy removes the risk of decompensation during a time when surgical options are severely constrained. Women with small, well-tolerated shunts can generally carry pregnancies safely with close monitoring, though the decision should be individualized with input from a cardiologist experienced in congenital heart disease.
Incidental Discovery on Chest CT
With the widespread use of chest CT for lung cancer screening, pulmonary embolism workup, and COVID-related imaging, more PAPVR is being found by accident than ever before. The anomalous vein is often visible as an unexpected vessel coursing toward the wrong destination. This can trigger anxiety for the patient and uncertainty for the ordering physician, who may not be familiar with the condition.
When PAPVR is found incidentally and the patient has no symptoms, the evidence supports a reassuring approach. The study of 80 unrepaired adults with intact septa and no surgical indication showed no functional decline over five years of follow-up.26PubMed Central. Outcomes of Adults With Unrepaired Partial Anomalous Pulmonary Venous Return and Intact Atrial Septum The practical recommendation is to get a cardiac MRI to quantify the shunt and assess right heart size, then follow up periodically. If the shunt is small and the right heart looks normal, surveillance alone is typically appropriate. If there is meaningful right-heart dilation or the shunt fraction is elevated, the conversation shifts toward potential repair.
How PAPVR Differs From a Patent Foramen Ovale or Standard ASD
People sometimes confuse PAPVR with a patent foramen ovale (PFO) or a secundum ASD because all three involve abnormal communication between the right and left sides of the heart. The distinction matters because the physiology, detection methods, and treatment approaches are different. A PFO is a flap-like remnant of fetal circulation that lets blood cross between the atria under certain conditions; it is present in about a quarter of adults and rarely causes hemodynamic problems. A secundum ASD is a true hole in the center of the atrial septum that creates a shunt but is usually detectable on standard echocardiography. PAPVR, by contrast, involves a misrouted vein, not a hole in the septum. It can exist with or without an ASD, and when it comes with a sinus venosus defect, the combination is easily missed on transthoracic echo because the defect sits at the upper edge of the septum where the ultrasound beam has poor resolution.
This confusion has real consequences. A patient with unexplained right-heart enlargement may get a standard echocardiogram, be told there is no ASD, and have the workup stop there. But the actual cause, an anomalous pulmonary vein draining into the superior vena cava above where the echo can see, goes undetected. Awareness that PAPVR exists as a distinct entity, separate from a hole in the septum, is one of the biggest gaps in routine clinical practice for this condition.