eMedicine Specialties > Pediatrics: Cardiac Disease and Critical Care Medicine > Cardiology

Pulmonary Artery Sling

Updated: Aug 26, 2008

Introduction

Background

Pulmonary artery sling is created by anomalous origin of the left pulmonary artery from the posterior aspect of the right pulmonary artery. The anomalous left pulmonary artery courses over the right mainstem bronchus and then from right to left, posterior to the trachea or carina and anterior to the esophagus, to reach the hilum of the left lung. This compresses the lower trachea and right mainstem bronchus, producing upper airway symptoms. Compression caused by the sling can produce obstructive emphysema, atelectasis of the right and left lungs, or both.

Associated tracheobronchial abnormalities may occur, especially complete tracheal rings and tracheomalacia. Hypoplasia and stenosis of tracheal segments occur and can potentiate the airway obstruction. Congenital heart defects are found in 50% of pulmonary artery sling cases, most commonly atrial septal defect, patent ductus arteriosus, ventricular septal defect, and left superior vena cava.

Other organ system abnormalities may occur. These include imperforate anus, Hirschsprung disease, biliary atresia, and genitourinary defects. Abnormalities of ovaries, vertebrae, thyroid gland, and pulmonary parenchyma have been reported.

Pathophysiology

As the left pulmonary artery passes posteriorly and caudally to the right main-stem bronchus and to the left behind the trachea, tracheal and bronchial compression occurs. The course of the anomalous left pulmonary artery to the right of the trachea produces deviation of the lower trachea to the left with resulting compression of the right mainstem bronchus and lower trachea. This results in airway obstruction that primarily affects the right lung, although compression of the lower trachea and left mainstem bronchus can result in bilateral obstruction.

Other abnormalities in the arterial supply to one or both lungs can be seen in association with this abnormality. On occasion, the anomalous pulmonary artery may supply only the left upper lobe with normal pulmonary arterial supply to the left lower lobe. In addition, partial anomalous supply of the right upper lobe of the lung from the anomalous left pulmonary artery has been described.

Frequency

United States

This is a rare defect, and frequency is not determined.

International

The international frequency is unknown.

Mortality/Morbidity

In severely affected infants, death can occur in the early months of life. Survival is unlikely without surgical intervention. Mortality varies and has been reported to be relatively high in previous studies. The major contributor to postoperative mortality is the high frequency of bronchial and tracheal abnormalities in this group of patients. Early, aggressive intervention may minimize the mortality caused by these associated lesions.¹

Morbidity includes frequent episodes of stridor and respiratory distress with or without wheezing and cyanosis. Recurrent pneumonia can occur.

Race

No racial predilection is known.

Sex

No sex predilection is apparent.

Age

Symptoms, including respiratory distress manifested by stridor, recurrent pneumonia, wheezing, and cyanosis, typically occur within the first month of life. Dysphagia is rare, but obstructive apnea may occur. These patients tend to be more symptomatic and to present even earlier than those with a vascular ring due to a double aortic arch.

Clinical

History

In patients with pulmonary artery sling, the history is predictable and usually not subtle. Most infants are affected within the first few weeks of life and present with stridor, respiratory distress, cyanosis, wheezing, and/or pneumonia.

Physical

Physical examination demonstrates respiratory distress with stridor, dyspnea, and wheezing. When tracheal obstruction is present, the infant may have constant retractions and tachypnea. If a congenital heart defect is associated, its typical physical findings can be identified.

Causes

The specific etiology of the pulmonary artery sling is unknown.

Differential Diagnoses

Stridor
Vascular Ring, Double Aortic Arch
Vascular Ring, Right Aortic Arch

Workup

Imaging Studies

In pulmonary artery sling, the following imaging studies may be indicated:

Chest radiography: The lower trachea is deviated to the left and may appear compressed on its right side. Hyperinflation of the right lung may be seen because of impingement on and compression of the right main stem bronchus. The left lung also may appear hyperinflated because of obstruction at the level of the carina and the left main stem bronchus. In patients with severe obstruction, atelectasis of a single lung or single lobe may be observed. The lateral view may reveal a density anterior to the esophagus and posterior to the trachea just above the carina. This is the left pulmonary artery viewed on end.
Barium swallow: The barium swallow is the diagnostic procedure of choice. An anterior indentation of the esophagus on the lateral projection is diagnostic of pulmonary artery sling. The esophagus is usually displaced to the right in the frontal projection and demonstrates an oblique impression immediately posterior to the carina.
Echocardiography: In the usual coronal-plane suprasternal-notch images, absence of normal bifurcation of the main pulmonary artery into right and left pulmonary arteries is visible. The left pulmonary artery appears to be absent. However, examination of the right pulmonary artery reveals the left pulmonary artery arising from its posterior surface. The left pulmonary artery can be followed posterior to the trachea and anterior to the esophagus. It passes anterior to the descending aorta and enters the hilum of the left lung. Echocardiography also reveals any associated congenital heart defects.

Bronchoscopy is generally not recommended. If performed, tracheal compression is noted, and accompanying tracheomalacia, tracheal stenosis, or both is common.² Some recommend bronchoscopic evaluation of selected surgical candidates because surgical reconstruction of the trachea or bronchi may be necessary if the airway compromise is severe.

Currently, MRI or magnetic resonance angiography, CT scanning, or a combination can be helpful in delineating the details of the anatomy, as well as in 3-dimensional reconstruction of the anatomy of the sling as it relates to the airway anatomy.

Procedures

Cardiac catheterization and angiography: Diagnosis can usually be noninvasively established. Pulmonary artery angiography may be advisable to delineate anatomic details prior to surgical correction. This permits diagnosis of variations in right and left pulmonary artery anatomy that may not be apparent from noninvasive studies and that can alter the surgical approach. Origin and course of the anomalous left pulmonary artery is best revealed by contrast injection into the main pulmonary artery filming in an oblique view with steep cranial angulation of 60-70 º.

Treatment

Medical Care

In patients with pulmonary artery sling, medical care is supportive until the patient can undergo definitive surgical correction. Hypoxemia and respiratory distress should be treated with supplemental oxygen and endotracheal (ET) intubation if indicated. Treat pneumonia with appropriate antibiotics. Stabilize the patient and make arrangements for surgery as soon as possible. Infants without airway obstruction and with minimal symptoms may not require surgical intervention. However, this scenario is the rare exception.

Surgical Care

Survival of symptomatic infants is unlikely without early surgical intervention. In 1954, Potts and Hollinger reported the first description of surgical repair of this lesion.³ Surgery involves division of the anomalous left pulmonary artery and reanastomosis to the main pulmonary artery anterior to the trachea. Although this can be performed from a left thoracotomy, approach from a midline sternotomy with cardiopulmonary bypass may offer more control.

Mortality varies and has been reported to be relatively high in previous studies. The major contributor to postoperative mortality is the high frequency of bronchial and tracheal abnormalities in this group of patients. Early, aggressive intervention may minimize the mortality caused by these associated lesions. If airway stenosis is severe, patients may require surgical reconstruction of the obstructed bronchi or trachea at the time of reimplantation of the anomalous left pulmonary artery.

Surgical survivors are usually free of significant symptoms at long-term follow-up. However, some degree of airway obstruction may persist in as many as 45% of patients.

Consultations

Pediatric cardiologist
Cardiovascular surgeon experienced in congenital heart defect surgery
Radiologist

Diet

No specific dietary considerations are needed.

Activity

Normal activity is indicated after surgical repair unless significant airway obstruction persists.

Medication

No specific medications directly influence this abnormality. Pneumonia requires appropriate antibiotics.

Follow-up

Further Inpatient Care

Inpatient care in patients with pulmonary artery sling may be required for symptoms of airway obstruction and/or pneumonia.
After surgical repair, these same symptoms may persist, although they should improve over time.

Further Outpatient Care

Close follow-up care after surgery is required.
Although airway symptoms should improve, follow patients closely, especially during times of upper respiratory infections.
Similarly, monitor this group of patients closely for the possibility of left pulmonary artery stenosis after reimplantation of the vessel. This can be noninvasively assessed with echocardiography but rarely may require follow-up pulmonary artery angiography.

Transfer

Patients hospitalized with significant stridor, in whom a vascular ring or pulmonary artery sling is suspected, should be transferred to a facility that can provide pediatric cardiology and pediatric cardiovascular surgery services.

Deterrence/Prevention

No preventive measures are known.

Complications

Because of associated tracheomalacia, tracheal stenosis, and/or bronchial stenosis, postoperative symptoms of airway obstruction are common. Left pulmonary artery stenosis may occur and can be progressive.

Prognosis

With early diagnosis and surgical correction, prognosis is good.
Surgical mortality is increased by coexisting tracheal or bronchial stenosis.
Surgical survivors may be free of significant symptoms at long-term follow-up; however, because many demonstrate some persistent airway obstruction, they should be closely observed for both airway as well as pulmonary artery complications.

Patient Education

Parents should be educated about issues with regard to airway obstruction and tracheobronchial toilet. Patients in the immediate postoperative period still may be at risk during respiratory illnesses because of increased secretions. Over time, with healing and improvement of the tracheomalacia/tracheal stenosis, these symptoms should improve.

Miscellaneous

Medicolegal Pitfalls

Failure to diagnose stridor in a young infant
Late diagnosis of pulmonary artery sling
Failure to monitor patients postoperatively for persistent airway obstruction

References

Sade RM, Rosenthal A, Fellows K, et al. Pulmonary artery sling. J Thorac Cardiovasc Surg. Mar 1975;69(3):333-46. [Medline].
Loukanov T, Sebening C, Springer W, et al. Simultaneous management of congenital tracheal stenosis and cardiac anomalies in infants. J Thorac Cardiovasc Surg. Dec 2005;130(6):1537-41. [Medline].
Potts W, Holinger P. Anomalous left pulmonary artery causing obstruction to the right main stem bronchus. JAMA. 1954;155:1409.
Freedom R, Culham J. The Angiography of Congenital Heart Disease. 1998.
Grover FL, Norton JB Jr, Webb GE, et al. Pulmonary sling. Case report and collective review. J Thorac Cardiovasc Surg. Feb 1975;69(2):295-300. [Medline].
Morrow R, Huhta J. Aortic arch and pulmonary artery anomalies. In: The Science and Practice of Pediatric Cardiology. 1990:1444-7.
Niwayama G. Unusual vascular ring formed by the anomalous left pulmonary artery, with tracheal compression. Am Heart J. Mar 1960;59:454-61. [Medline].
Semple MG, Bricker L, Shaw BN, Pilling DW. Left pulmonary artery sling presenting as unilateral echogenic lung on 20-week detailed antenatal ultrasound examination. Pediatr Radiol. Aug 2003;33(8):567-9. [Medline].
Tesler UF, Balsara RH, Niguidula FN. Aberrant left pulmonary artery (vascular sling): report of five cases. Chest. Oct 1974;66(4):402-7. [Medline].

Keywords

pulmonary artery sling, vascular ring, vascular sling, emphysema, atelectasis, atrial septal defect, patent ductus arteriosus, ventricular septal defect, left superior vena cava, imperforate anus, Hirschsprung disease, biliary atresia, genitourinary defects, airway obstruction, stridor, respiratory distress, cyanosis, pneumonia

Contributor Information and Disclosures

Author

Stuart Berger, MD, Professor of Pediatrics, Division of Cardiology, Medical College of Wisconsin; Chief of Pediatric Cardiology, Medical Director of Pediatric Heart Transplant Program, Medical Director of The Heart Center, Children's Hospital of Wisconsin
Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, and Society for Cardiac Angiography and Interventions
Disclosure: Nothing to disclose.

Medical Editor

Ira H Gessner, MD, Professor Emeritus, Pediatric Cardiology
Ira H Gessner, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, American Pediatric Society, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation

Managing Editor

Hugh D Allen, MD, Professor, Department of Pediatrics, Division of Pediatric Cardiology and Department of Internal Medicine, Ohio State University College of Medicine
Hugh D Allen, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American Heart Association, American Pediatric Society, American Society of Echocardiography, Society for Pediatric Research, Society of Pediatric Echocardiography, and Western Society for Pediatric Research
Disclosure: Nothing to disclose.

CME Editor

Gilbert Herzberg, MD, Assistant Professor, Department of Pediatrics, Section of Pediatric Cardiology, New York Medical College
Gilbert Herzberg, MD is a member of the following medical societies: American Academy of Pediatrics
Disclosure: Nothing to disclose.

Chief Editor

Steven R Neish, MD, SM, Director of Pediatric Cardiology Fellowship Program, Associate Professor, Department of Pediatrics, Baylor College of Medicine
Steven R Neish, MD, SM is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, and American Heart Association
Disclosure: Nothing to disclose.

Further Reading