---
title: Partial anomalous pulmonary venous return
description: What partial anomalous pulmonary venous return is, why some of the blood from the lungs goes to the right side of the heart, how the defect is found, how surgery corrects it and when urgent help is needed.
type: disease
aliases:
  - PAPVR
  - PAPVC
  - Partial anomalous pulmonary venous drainage
  - Partial anomalous pulmonary venous connection
  - Scimitar syndrome
  - Sinus venosus defect with PAPVR
sources:
  - tier: guideline
    org: minzdrav-rf
    title: Частичный аномальный дренаж легочных вен (ЧАДЛВ)
    year: 2024
    url: https://cr.minzdrav.gov.ru/view-cr/861_1
  - tier: guideline
    org: esc
    title: 2020 ESC Guidelines for the management of adult congenital heart disease
    year: 2020
    doi: 10.1093/eurheartj/ehaa554
    url: https://doi.org/10.1093/eurheartj/ehaa554
  - tier: reference
    org: msd-manuals
    title: Atrial Septal Defect (ASD)
    year: 2023
    url: https://www.msdmanuals.com/professional/pediatrics/congenital-cardiovascular-anomalies/atrial-septal-defect-asd
sources_checked: 2026-10-13
review: null
---

Partial anomalous pulmonary venous return (PAPVR) is a congenital heart defect in which one or more, but not all, of the <Structure id="pulmonary-veins">pulmonary veins</Structure> drain not into the <Structure id="left-atrium">left atrium</Structure> but into the <Structure id="right-atrium">right atrium</Structure>, the coronary sinus or the venae cavae.<Cite n={1} /> If all the pulmonary veins drain abnormally, it is a different defect: [total anomalous pulmonary venous return](../total-anomalous-pulmonary-venous-return/).<Cite n={1} />

In PAPVR, some of the oxygen-rich blood from the lungs returns to the right side of the heart and goes back to the lungs, so the right side of the heart is overloaded with extra blood, just as in an [atrial septal defect](../atrial-septal-defect/).<Cite n={[1, 2]} /> If the shunt is significant, the defect is corrected with surgery; the operation is usually planned rather than urgent.<Cite n={1} />

<Diagram name="partial-anomalous-pulmonary-venous-return">
  <p slot="normal">
    Normally four pulmonary veins, two right and two left, carry blood from the lungs into the left
    atrium.<Cite n={1} />
  </p>
  <p slot="disease">
    The diagram shows one form of PAPVR, with a sinus venosus defect.<Cite n={1} />
    The right upper pulmonary vein drains not into the left atrium but into the superior vena cava, close to where it joins the right atrium.<Cite n={[1, 2]} /> There is an opening high in the wall between the atria, near where the superior vena cava enters the right atrium.<Cite n={[1, 2, 3]} /> Through this opening and through the
    abnormally draining vein, blood from the lungs passes to the right side of the heart, a
    left-to-right shunt.<Cite n={1} /> The right atrium and right ventricle are overloaded with extra
    blood and become enlarged.<Cite n={[1, 2]} />
  </p>
</Diagram>

## Why it happens

<Patient>

The defect forms before birth: in the embryo, some of the pulmonary veins keep a connection with the veins that carry blood from the organs of the body and do not connect to the left atrium.<Cite n={1} /> It is a rare defect: according to post-mortem (autopsy) studies, it is found in 0.6–0.9% of cases.<Cite n={1} />

As a rule, PAPVR comes with an opening between the atria, but occasionally the wall between them is intact.<Cite n={1} /> Most often it is the right pulmonary veins that drain abnormally, in up to 90% of cases.<Cite n={1} /> The most common variant is the right upper pulmonary vein draining into the superior vena cava.<Cite n={2} /> Doctors describe the defect by stating which veins drain abnormally and where, and whether there is an opening between the atria.<Cite n={1} />

A special rare variant is **scimitar syndrome**: the right pulmonary veins run downwards and drain into the inferior vena cava.<Cite n={[1, 2]} /> Without treatment it takes a much more severe course and has a poor outlook, so in this case surgery is recommended as soon as the diagnosis is made.<Cite n={1} />

</Patient>

<Student>

When embryonic development is disturbed, the pulmonary veins may partly retain a haemodynamic connection with the cardinal veins and/or the developing portal system, having lost their connection with the LA.<Cite n={1} /> Mixed drainage of several pulmonary veins is possible.<Cite n={1} />

According to the Russian Ministry of Health guideline, about 65% of all cases of PAPVR are the form with a sinus venosus ASD: the right upper lobe and, less often, middle lobe veins drain into the ostial part of the superior vena cava, and a sinus venosus ASD is an obligatory component of the defect.<Cite n={1} /> This is a defect in the posterior part of the septum adjacent to the superior or inferior vena cava, frequently associated with anomalous return of the right upper or lower pulmonary veins.<Cite n={3} /> The ESC guideline for adults gives a different share, among all ASDs: the superior sinus venosus defect accounts for 5% of ASDs.<Cite n={2} /> Anomalous pulmonary venous connection can also be isolated, without an ASD; in that case, according to the ESC, there is no potential for a right-to-left shunt.<Cite n={2} />

The size of the left-to-right shunt at the venoatrial level depends on the number and size of the anomalously draining veins.<Cite n={1} /> The physiological effect of right heart volume overload is similar to that of an ASD.<Cite n={2} />

Scimitar syndrome is the infracardiac form: the right pulmonary veins drain into the inferior vena cava.<Cite n={1} /> It is characterised by dextrocardia, hypoplasia of the right lung and of the right pulmonary artery system, and large aortopulmonary collaterals to the lower lobe of the right lung, which lead to secondary changes in the pulmonary arterioles, that is, [pulmonary hypertension](../pulmonary-hypertension/); 70% of patients have an ASD or a patent foramen ovale.<Cite n={1} />

</Student>

<HeartModel highlight={['pulmonary-veins', 'superior-vena-cava', 'right-atrium', 'left-atrium', 'interatrial-septum']} />

The 3D model shows a normal heart: highlighted are the pulmonary veins, which normally drain into the left atrium, the <Structure id="superior-vena-cava">superior vena cava</Structure>, both atria and the <Structure id="interatrial-septum">wall between them</Structure>.<Cite n={1} />

## Symptoms

<Patient>

How the defect shows itself depends on how much blood goes to the right side of the heart, and that depends on the number and size of the abnormally draining veins.<Cite n={1} /> If one or two veins drain abnormally, the defect develops slowly and shows itself in later childhood.<Cite n={1} /> It is often found by chance during a routine check-up of "healthy" children or when heart rhythm problems appear.<Cite n={1} />

Most babies with PAPVR grow and develop normally.<Cite n={1} /> Parents should be alert to frequent colds that turn into bronchitis or pneumonia.<Cite n={1} /> Complaints about the heart usually appear in adolescence.<Cite n={1} />

Possible signs of the defect:<Cite n={1} />

- a child or adult copes less well with exercise and becomes breathless on exertion;
- frequent respiratory infections;
- signs of [heart failure](../heart-failure/), usually mild or moderate;
- heart rhythm problems caused by stretching of the right atrium;
- in babies, sweating, feeding difficulties and slow physical development.

If more than two veins drain abnormally, there is almost no wall between the atria, or the child has scimitar syndrome, the defect may show itself as early as the first year of life.<Cite n={1} /> These children lag behind in development and may have breathlessness, bluish skin on exertion and marked heart failure.<Cite n={1} />

</Patient>

<Student>

In adults, according to the ESC, the long-term sequelae of anomalous pulmonary venous connection reflect right heart volume overload and are similar to the sequelae of ASDs.<Cite n={2} /> In ASD, the majority develop symptoms beyond the fourth decade: reduced functional capacity, exertional dyspnoea and palpitations due to supraventricular tachyarrhythmias.<Cite n={2} />

On auscultation there is a systolic murmur, loudest in the second to third intercostal space at the left sternal border; the second heart sound over the pulmonary artery is widely split regardless of the phase of respiration.<Cite n={1} /> The ECG shows RV hypertrophy, incomplete right bundle branch block and signs of right atrial overload.<Cite n={1} />

</Student>

## How it is diagnosed

<Patient>

The diagnosis is based on an [ECG](../../diagnostic/ecg/), a heart ultrasound ([echocardiography](../../diagnostic/echocardiography/)), a contrast CT or MRI scan and, if needed, cardiac catheterisation.<Cite n={1} /> The main method is echocardiography.<Cite n={[1, 2]} />

A sinus venosus defect is hard to see clearly on a standard ultrasound scan through the chest: an accurate diagnosis usually needs transoesophageal echocardiography, in which the probe is passed into the oesophagus (gullet); an MRI or CT scan is an alternative.<Cite n={[1, 2]} /> A contrast CT or MRI scan shows exactly where the veins drain.<Cite n={1} />

</Patient>

<Student>

PAPVR is suspected on echocardiography when the characteristic flow from the right or left pulmonary veins into the left atrium is absent on colour Doppler.<Cite n={1} /> The ratio of pulmonary to systemic blood flow (Qp/Qs) must be determined; a ratio above 1.5 is considered significant.<Cite n={1} />

For most patients, contrast CT or MRI is enough for additional imaging; in scimitar syndrome, angiography is needed to plan the surgical approach.<Cite n={1} /> Most patients have no specific radiographic picture; in scimitar syndrome, the shadow of the descending dilated pulmonary veins is seen, resembling a Turkish sabre (scimitar), hence the name.<Cite n={1} />

</Student>

## How it is treated

<Patient>

If one or two veins drain abnormally, the defect usually causes few or no symptoms, and medicines are not needed.<Cite n={1} /> Medicines are prescribed for heart failure, heart rhythm problems, pulmonary hypertension or if the operation has to be postponed; the doctor decides which ones.<Cite n={1} />

The defect is corrected with surgery; it is recommended if the shunt is significant.<Cite n={1} /> The Russian Ministry of Health guideline advises doing it in childhood, before complications develop.<Cite n={1} /> The operation is usually not urgent, but it is done earlier if bronchitis and pneumonia become more frequent and the right chambers of the heart are enlarging.<Cite n={1} />

During the operation, the opening in the wall between the atria is closed with a patch, and the blood from the abnormally draining veins is directed into the left atrium through a patch tunnel inside the right atrium.<Cite n={1} /> There are several ways of doing this operation; which one is chosen depends on where and how high the veins drain.<Cite n={1} /> A sinus venosus defect does not close on its own and cannot be closed with a device passed through a blood vessel (an occluder).<Cite n={3} /> The operation should be done by a surgeon who specialises in congenital heart defects.<Cite n={2} />

After timely surgery, the outlook is good.<Cite n={1} /> But narrowing of the operated veins, a residual shunt between the atria and heart rhythm problems can occur, so lifelong follow-up is needed after the operation: with a paediatric cardiologist until the age of 18, then with a cardiologist or general physician, with an ECG, heart ultrasound and [Holter monitoring](../../diagnostic/holter-monitoring/).<Cite n={[1, 2]} /> For the first 6 months after the operation, or longer if a shunt remains, prevention of [endocarditis](../infective-endocarditis/) is needed before dental and other procedures that damage the skin or mucous membranes; it is agreed with the cardiologist.<Cite n={1} />

</Patient>

<Student>

Surgical treatment is recommended when Qp/Qs is above 1.5 (class I, level C); correction in childhood, before supraventricular tachyarrhythmias, dysfunction of both ventricles and PH develop, is preferred (class IIa, level C).<Cite n={1} /> According to the ESC, indications in adults follow the principles for ASD closure, with technical suitability for repair and operative risk taken into account; anomalous drainage of the vein of only one lobe rarely causes a volume load sufficient to justify surgery.<Cite n={2} />

For drainage of the right veins into the SVC or RA, three options for repair are described: intra-atrial patch tunnelling, its combination with patch enlargement of the SVC orifice, and the Warden procedure, used when the veins enter the SVC relatively high and tunnelling is not possible.<Cite n={1} /> Low-velocity flow increases the risk of thrombosis of the operated veins, particularly in scimitar syndrome.<Cite n={[1, 2]} />

In scimitar syndrome, surgical treatment is recommended as soon as the diagnosis is made, regardless of age and the severity of symptoms.<Cite n={1} /> The collaterals are closed by embolisation or surgically ligated; whether to preserve or resect the affected lobe of the right lung is decided separately.<Cite n={1} />

After repair, a residual interatrial shunt occurs in 5% of cases.<Cite n={1} /> After repair of a sinus venosus defect, SVC stenosis and stenoses of the redirected pulmonary veins can occur.<Cite n={2} /> Rhythm and conduction disturbances (supraventricular tachyarrhythmias, sick sinus syndrome, sudden cardiac death) occur both immediately after surgery and in the long term.<Cite n={1} /> Post-pericardiotomy syndrome and cardiac tamponade can occur a few weeks after surgery.<Cite n={1} />

</Student>

## When to call an ambulance

PAPVR does not usually need emergency care, but the Russian Ministry of Health guideline names conditions that require emergency hospital admission.<Cite n={1} /> Call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK) if an attack of palpitations or an irregular heartbeat comes with fainting or near-fainting, if breathlessness and swelling get rapidly worse, or if there are signs of a stroke: sudden weakness or numbness of an arm or leg, or problems with speech or vision, even if they are brief.<Cite n={1} /> As with any heart condition, call an ambulance for fainting, chest pain or severe breathlessness: this is the site's general safety rule, repeated at the bottom of every page.

<Quiz />