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Introduction

Background

Partial anomalous pulmonary venous connection (PAPVC) is a rare congenital cardiac defect. As the name suggests, in PAPVC, the blood flow from a few of the pulmonary veins return to the right atrium instead of the left atrium. Usually, a single pulmonary vein is anomalous. Rarely, all the veins from one lung are anomalous. Thus, some of the pulmonary venous flow enters the systemic venous circulation.

Embryologically, PAPVC is similar to total anomalous pulmonary venous connection (TAPVC); however, TAPVC differs in that all or most pulmonary venous vessels connect to the right side of the heart in TAPVC. Knowledge of the variation patterns of normal pulmonary venous drainage is necessary in order to diagnose PAPVC.

PAPVC from the right lung is twice as common as PAPVC from the left lung. The most common form of PAPVC is one in which a right upper pulmonary vein connects to the right atrium or the superior vena cava. This form is almost always associated with a sinus venosus type of atrial septal defect (ASD).

The right pulmonary veins can also drain into the inferior vena cava. The left pulmonary veins can drain into the innominate vein, the coronary sinus, and, rarely, the cavae, right atrium, or left subclavian vein.

Anatomically, PAPVC can involve a wide variety of connections, and can be subdivided into the following categories:

• PAPVC with ASD (80-90% cases): This is the most common type of PAPVC. The ASD is usually the sinus venosus type. Approximately 10% have a secundum ASD associated with this anomaly. The anomalous pulmonary vein, usually the right upper or middle pulmonary vein can either override the intra atrial septum (anomalous drainage) or can drain separately into the superior vena cava (true anomalous connection). Usually, the connection is unobstructed.
• PAPVC with intact atrial septum (isolated PAPVC): This is a very rare finding and mostly involves the anomalous drainage of the right upper pulmonary vein into the superior vena cava. Only 3% of patients had PAPVC from the left lung to the innominate vein.
• PAPVC with complex congenital heart disease (heterotaxia): This is usually seen with heterotaxia syndromes (polysplenia). Left atrial isomerism with a common atrium is observed. Because of the abnormal positioning of the intra-atrial septum, the right-sided pulmonary veins anastomose to the anatomically right-sided atrium, which is the atrium that also receives the inferior vena cava. About half of the cases may involve some degree of obstruction, either due to narrowing of a discrete area or due to diffuse hypoplasia of that vein. This condition is associated with presence of ipsilateral pulmonary arterial hypoplasia.
• Scimitar syndrome (right pulmonary vein to inferior vena cava with lung sequestration)
  • This syndrome is also known as Halasz syndrome, mirror-image lung syndrome, hypogenetic lung syndrome, epibronchial right pulmonary artery syndrome, vena cava bronchovascular syndrome, or congenital pulmonary venolobar syndrome.
  • It is more common in females and can be familial.
  • Usually, the anomaly involves the right lung; the left lung is very rarely involved.
  • In this syndrome, a venous anomaly, an arterial anomaly, and pulmonary anomaly are all observed.
  • The pulmonary abnormality includes a sequestered lobe of the lung that is separated from the bronchial tree and has nonfunctioning lung tissue. It is associated with hypoplastic or aplastic right pulmonary artery segments, hypoplastic or absent bronchi, hypoplasia of the right lung, horseshoe lung, and eventration of the hemidiaphragm.
  • The venous anomaly is PAPVC, usually with the right pulmonary veins draining into the inferior vena cava.
  • The arterial anomaly is a collateral arterial vessel (aberrant vessel) with blood supply of the right lower lobe from the abdominal aorta.
  • Dextropositioning of the heart due to right lung hypoplasia may be observed.
  • Usually, the atrial septum is intact.
  • About 25% cases have other associated congenital heart defects.

Pathophysiology

Numerous factors determine the ratio of pulmonary blood flow (Qp) to systemic flow (Qs). The shunt magnitude, expressed as the Qp:Qs ratio, and other factors determine development of symptoms and complications.

The most important factor is the number of pulmonary veins that drain into the systemic circulation. The more veins that anomalously drain, the more blood returns to the right side of the heart. Some authors have suggested that this defect becomes clinically significant when 50% or more of the pulmonary veins anomalously return.

In addition, the source of the returning blood plays a role in determining the clinical effect of the defect. In an individual who is upright, blood flow to the lungs is primarily directed to the lower and middle lobes. Therefore, more blood returns to the systemic venous circulation in individuals in whom the anomalous connection drains into either the right middle and lower lobes or the left lower lobe of the lung.

An associated cardiac defect, such as an ASD, may add to the left-to-right shunting.

In scimitar syndrome, the flow from the PAPVC causes a left-to-right shunt. Again, the number of anomalous veins involved determines the symptoms and signs. The aberrant artery may cause additional left-to-right shunt.

Over many years, excessive pulmonary venous return to the right side of the heart causes right atrial and ventricular dilation. This has numerous consequences, including risk of arrhythmia development, right-sided heart failure, and development of pulmonary hypertension.

A native PAPVC usually does not have any associated obstruction to venous drainage. However, obstruction may occur postoperatively due to baffle obstruction.

Frequency

United States

Most data regarding prevalence of this condition have been garnered from autopsy series that estimate an incidence of 0.4-0.7%. However, autopsy series may overestimate the clinical significance of this condition because many of these cases were asymptomatic; thus, the true incidence of patients who present antemortem with this condition is lower. Clinical diagnosis of isolated PAPVC is quite rare. PAPVC occurs in approximately 10% of patients with a proven ASD.

Mortality/Morbidity

Few data are available regarding mortality due to this lesion because mortality credited to the defect occurs only in adults and the diagnosis has historically been made at autopsy. Major morbidity, including arrhythmias, right-sided cardiac failure, and, rarely, pulmonary vascular disease, also primarily occurs in adults.

Race

No data regarding racial predilection are available.

Sex

The incidence is higher in the female population.

Age

PAPVC is a congenital defect. Clinical evidence of this congenital defect may not be apparent until the patient reaches middle age.

Clinical

History

Children with partial anomalous pulmonary venous connection (PAPVC) usually remain asymptomatic and are referred based on an incidentally noted cardiac murmur. Symptoms may occur in older patients and may be secondary to right-sided volume overload or pulmonary vascular obstructive disease.

Determining the natural history of this condition was difficult before the era of direct cardiac imaging (ie, echocardiography, cardiac catheterization) because the diagnosis was made only postmortem.

The development of complications from PAPVC clearly depends on how many pulmonary veins abnormally return to the right heart. A single anomalous vein is not usually hemodynamically significant and, hence, does not produce any symptoms.

About 10% of patients with an atrial septal defect (ASD) also have PAPVC and may have symptoms of right-sided overload.

• Dyspnea may occur in adults but is rare in children. A child may experience exercise intolerance as a symptom in cases in which more than 50% of pulmonary veins anomalously drain.
• Palpitations may reflect cardiac arrhythmias, which are almost always supraventricular in origin. These arrhythmias may be due to right atrial dilatation and, hence, may present at older age. They can also occur postoperatively due to atriotomy.
• Hemoptysis is a rare symptom that reflects either chest infection or the development of pulmonary vascular disease.
• Chest pain may be evidence of right-heart ischemia but does not occur in childhood. More commonly, chest pain may be a manifestation of recurrent bronchitis.
• Associated defects (either cardiac or extracardiac) can produce symptoms.
• Peripheral edema can occur in adults with cardiac failure.

The severity of symptoms in scimitar syndrome depends on several factors, including degree of pulmonary hypertension and the severity and frequency of chest infections. Scimitar syndrome can present in neonates, children, and adults and is related to the degree of pulmonary hypoplasia.

Physical

Physical examination findings are usually more revealing than the history, but positive findings depend on the volume of abnormal pulmonary venous return to the right heart. If only a single vein is anomalous, the physical examination findings may be normal. In a patient with a larger volume of abnormal veins, physical examination findings are similar to those of an uncomplicated ASD. These findings include the following:

• Left parasternal lift reflects right ventricular dilation. Impulse in the second left intercostal space reflects pulmonary artery dilation.
• A soft systolic ejection murmur is heard over the pulmonary area, reflecting turbulence in the pulmonary trunk due to increased right ventricular ejection volume. The second heart sound is always widely split but may have normal respiratory variation.
• In healthy individuals, inspiration increases systemic venous return to the right heart, causing a delay in the pulmonic closure component of the second sound. This phenomenon also occurs in patients with PAPVC who have an intact atrial septum. However, in patients with PAPVC and ASD, volume flow into the right heart is always increased, and respiration further augments that flow. Therefore, splitting of S2 proceeds from wide during expiration to wider during inspiration. This does not occur in patients with a significant ASD, in whom second heart spitting is wide and fixed. In the presence of an ASD, variations in systemic venous return during respiration are counterbalanced by reciprocal changes in flow through the ASD, maintaining total right ventricular flow more or less constant. A mid-diastolic murmur due to increased transtricuspid right ventricular filling may be heard over the tricuspid valve area at the lower left sternal border.
• Cyanosis does not occur, even in older patients in whom pulmonary hypertension develops, because a right-to-left shunt cannot develop in the absence of an atrial septal communication.
• Right-sided heart failure signs in adults include hepatomegaly, jugular venous distension, ascites, and peripheral edema.
• Pulmonary vascular disease may occur in older adults, although this is rare. Clinical signs of pulmonary hypertension include a right ventricular parasternal lift, absence of systolic murmur, narrowly split S2 with a loud pulmonic component, and, occasionally, an early, high-frequency murmur of pulmonic regurgitation. Cyanosis does not occur in the presence of an intact atrial septum.

Causes

No causes of this condition are known. No evidence has implicated common teratogens (eg, drugs, infections) in the genesis of PAPVC. No evidence for a genetic predisposition has been reported.

Workup

Imaging Studies

Imaging studies in partial anomalous pulmonary venous connection (PAPVC) include the following:

• Chest radiography
• Cardiomegaly noted on chest radiography may be the initial reason for referral of a child with PAPVC. Other findings may include a dilated main pulmonary artery and increased pulmonary arterial vascular markings. However, chest radiography findings may be grossly normal.
• Anomalous connection of one or more veins from the left lung into a left vertical vein that drains into the left innominate vein can create widening of the left upper mediastinal shadow. Rarely, the increased flow volume may also be sufficient to dilate the superior vena cava (SVC), widening the upper right mediastinal shadow. This can simulate the so-called "snowman" heart shape described in total anomalous pulmonary venous return to a left vertical vein.
• In its classic appearance, scimitar syndrome causes the "scimitar sign." This sign is a linear opacity, usually (but not always) found at the base of the right lung, that widens as it courses inferiorly and ends in the inferior vena cava. It is associated with dextroposition of the heart due to right lung hypoplasia. The scimitar sign can be obscured by a significant dextropositioning of the heart.
• Echocardiography
• PAPVC has been diagnosed in utero. In children, echocardiography is the study of choice; however, the lesion can be easily missed if routine echocardiography does not incorporate definition of the entire pulmonary venous return. The size or the diameter of the pulmonary veins should be determined by 2-dimensional (2D) echocardiography. Spectral Doppler study of the individual pulmonary veins is also important to determine obstruction to the flow
• In most patients, transthoracic echocardiography can be performed to diagnose PAPVC and obviate the need for cardiac catheterization. A high index of suspicion for the presence of the lesion is helpful to properly diagnose the condition.
• In adults, contrast echocardiography can help with the diagnosis. Agitated saline in a left arm vein can reveal a negative contrast in the innominate vein at the side of the anomalous venous drainage from a left pulmonary vein.
• Transesophageal echocardiography is also performed for better delineation of the veins, especially in the adult population.
• Right ventricular dilation may be the first observation that indicates the presence of abnormal venous drainage. The sonographer must identify all 4 pulmonary veins and visualize their connections to the heart. The atrial septum also needs to be evaluated for defects.
• MRI
• MRI is rapidly becoming the procedure of choice for further investigation of PAPVC.¹ Although echocardiography findings suggest the PAPVC, all the pulmonary veins may not be identified, especially in adults. With refinements in technology rapidly improving the quality of images obtained, fewer children require invasive angiography. Cardiac catheterization may be a more preferable diagnostic tool in infants with complex congenital heart conditions in whom PAPVC is one component.
• Julsrud and Ehman (1985) reported that use of MRI in the imaging of PAPVC revealed a characteristic sign termed the "broken ring sign."² In individuals with normal anatomy, a transverse MRI demonstrates a ringlike structure derived from mediastinal fat that surrounds the SVC. In healthy individuals, this ring is broken only at the point of entry of the azygous vein into the SVC. In some patients with partial anomalous pulmonary venous return, the ring of fat also appears to be breached or broken at the site of entry of the anomalous vein.
• CT scanning: Contrast-enhanced CT scanning is an alternative imaging modality to detect PAPVC when transthoracic images are limited, especially in older children and adults.

Other Tests

• Electrocardiography (ECG) findings may be normal. They may demonstrate right ventricular dilation manifested by an rSR pattern in right chest leads or right ventricular hypertrophy.
• Right atrial dilatation may be observed with a P pulmonale on ECG.
• Postoperative sinus node dysfunction can occur due to damage to the sinus node or its blood supply. This can manifest as significant bradycardia or junctional rhythm or sinus pauses of 3 seconds or more in duration.
• Arrhythmias, typically supraventricular tachycardia, atrial flutter, and fibrillation, may be observed, either due to right atrial enlargement at older age or secondary to atriotomy and sutures.

Procedures

• Cardiac catheterization is rarely necessary for precise anatomic diagnosis and hemodynamic evaluation.
• Right heart pressures are normal in the pediatric patient.
• Oxygen sampling may identify the location of an anomalous vein. Oxygen saturation in the right atrium that is higher than that found in the SVC strongly indicates PAPVC to the right atrium, provided that an atrial septal defect (ASD) has been ruled out.
• Qp:Qs can be calculated.
• Entering the anomalous vein with a catheter and injecting contrast confirms the diagnosis.
• Selective right and left pulmonary artery angiography that reveals pulmonary venous return for each lobe from each lung provides definitive anatomic diagnosis.
• Complications of catheterization include bleeding at the vascular entry site, infection, decreased pulses distal to an arterial entry site, and arrhythmia induction.

• Treatment

  Medical Care

  Medical therapy of partial anomalous pulmonary venous connection (PAPVC) is not indicated for asymptomatic patients. Heart failure in adults can be managed with diuretics, cardiac glycosides, afterload reduction, and beta blockade. Arrhythmias should be appropriately treated.

  Surgical Care

  Definitive treatment for PAPVC is surgical repair. Indications for surgical repair are controversial.

  One school of thought claims that all children should undergo repair because of the exceptionally low morbidity and mortality following this surgical procedure. Others suggest that appropriate criteria include a significant left-to-right shunt (Qp:Qs of about 2:1 or more) or such as an entire lung that anomalously drains, before recommending surgery.

  Operative technique depends on the site of the anomalous vein or veins. The usual approach is a midline sternotomy and cardiopulmonary bypass. Surgical treatment of associated lesions may be necessary.

  For the PAPVC to the superior vena cava (SVC), the repair techniques may include internal patch technique, with or without SVC enlargement, or the caval division technique with atriocaval anastomosis (Warden technique). Children with internal patch technique must be observed for obstruction of the SVC with SVC syndrome, sick sinus syndrome, obstruction of the pulmonary veins, and supraventricular tachyarrhythmias.

  Consultations

  • Cardiologist
  • Cardiothoracic surgeon

  Diet

  No specific diet is recommended or prohibited.

  Activity

  No limitation on activity is necessary in the pediatric patient.

  Medication

  Medication is not currently a component of care in this condition. See Treatment.

  Further Inpatient Care

  • Routine postoperative care of the patient who has undergone cardiac surgery for partial anomalous pulmonary venous connection (PAPVC) should be performed.
  • Pain control should be optimal to reduce the risk of atelectasis.
  • Anticipate early extubation unless contraindications are recognized; these include excessive chest tube drainage, hemodynamic instability, and oversedation.
  • Encourage early mobilization.
  • Monitor for atrial flutter, atrial fibrillation, and sinus node dysfunction.

  Further Outpatient Care

  • Intermittent follow-up to assess right heart size and pressures and cardiac function and rhythm is necessary in patients who did not undergo surgical treatment. With a significant shunt, the pulmonary artery pressures can be elevated, and pulmonary vascular resistance can increase with age.
  • Postoperatively, possible obstruction of the pulmonary veins and superior vena cava (SVC) should be evaluated with echocardiography.
  • Regular electrocardiography (ECG) and 24-hour ambulatory ECG are also indicated to monitor for atrial arrhythmias.

  Transfer

  • Patients should be transferred to an institution skilled in pediatric cardiology and pediatric cardiac surgery for assessment and treatment.

  Deterrence/Prevention

  • PAPVC is a congenital cardiac defect with no known cause and possibly has a multifactorial origin, including a genetic component. It is also seen with Turner syndrome.

  Complications

  • No significant complications develop in pediatric patients who do not undergo surgery for a sinus venosus atrial septal defect (ASD) repair with internal patch technique to include the right upper pulmonary vein in the left atrium. However, other types of repair may be associated with complications such as SVC syndrome, pulmonary venous obstruction, atrial arrhythmias, and sick sinus syndrome.
  • Arrhythmias may occur in adults with unrepaired PAPVC secondary to chronic right atrial enlargement due to volume overload.
  • Cardiac failure and, very rarely, pulmonary hypertension may develop in adults.
  • Patients with scimitar syndrome may be asymptomatic or may have symptoms related to lung pathology, including recurrent pneumonias.

  Prognosis

  • Prognosis is excellent for patients with PAPVC. The perioperative mortality rate is comparable to that for ASD repair (<0.1%).
  • Prognosis becomes more guarded if the lesion is undetected for a long period and if complications, particularly pulmonary hypertension, develop.
  • The only postoperative death in the series by Gustafson et al involved a woman with pulmonary hypertension.³

  Patient Education

  • Advise patient and parents regarding long-term risks if a large shunt remains unrepaired.
  • If pulmonary hypertension has developed, outline the risks of pregnancy, including death.

  Miscellaneous

  Medicolegal Pitfalls

  • Failure to diagnose partial anomalous pulmonary venous connection (PAPVC)⁴
  • Late diagnosis of PAPVC
  • Risk of pulmonary hypertension