A left pulmonary artery sling, or LPAS, is a rare congenital condition involving the blood vessels connected to the heart and lungs. In this condition, the left pulmonary artery, which is supposed to carry blood from the heart to the left lung, originates from an unusual location. Instead of branching off the main pulmonary artery, it arises from the right pulmonary artery.
This forces the left pulmonary artery to follow an atypical path to reach the left lung. It travels between the trachea (windpipe) and the esophagus (the tube that carries food to the stomach). This course creates a “sling” of vascular tissue that wraps around the airway, which can put pressure on these structures.
Anatomical Formation and Associated Conditions
A left pulmonary artery sling develops very early in fetal life. It stems from an abnormality in the formation of the sixth aortic arch, a primitive structure that develops into the pulmonary arteries. Normally, this arch system evolves in a way that allows the left pulmonary artery to connect directly to the main pulmonary artery, anterior to the trachea.
In LPAS, a failure in this process leads to the left pulmonary artery budding off the right pulmonary artery instead. This misplaced vessel then travels from right to left, passing behind the trachea and in front of the esophagus. This path can compress the lower part of the trachea and the right main bronchus, which is the airway passage into the right lung. While it is often grouped with vascular rings, it does not form a complete circle around both the trachea and esophagus.
Many infants with LPAS also have other congenital conditions. The most common of these is congenital tracheal stenosis, which involves a narrowing of the windpipe due to the presence of complete, O-shaped cartilage rings instead of the usual C-shaped rings. Other associated issues can include intracardiac defects, such as an atrial septal defect or a ventricular septal defect. The presence and severity of these associated anomalies often influence the clinical outcome.
Symptoms and Diagnostic Process
Symptoms of a left pulmonary artery sling are driven by airway compression and often appear in infancy, within the first year of life. Common symptoms include:
- Biphasic stridor, a high-pitched, noisy breathing sound audible during both inhalation and exhalation
- Persistent wheezing
- Episodes of respiratory distress
- Recurrent lung infections
- Cyanosis, a bluish discoloration of the skin, particularly during periods of increased distress
- Dysphagia, or difficulties with feeding, due to esophageal compression
Confirming the diagnosis involves advanced imaging tests. An echocardiogram, an ultrasound of the heart, is often one of the first tests performed to visualize the abnormal origin of the left pulmonary artery and assess for any co-existing cardiac defects. For a more detailed view, a computed tomography (CT) scan or magnetic resonance imaging (MRI) is used. These scans provide a clear, three-dimensional picture of the artery’s path and its relationship to the trachea and esophagus.
A bronchoscopy, where a small camera is inserted into the airway, may also be performed. This allows for direct visualization of the external compression on the trachea and helps to evaluate the presence and extent of tracheal stenosis.
Surgical Correction
The standard treatment for symptomatic left pulmonary artery sling is surgical repair to relieve airway compression. The operation is performed during infancy to prevent long-term damage to the lungs and trachea. The goal is to move the misplaced artery so it no longer passes between the trachea and esophagus, while ensuring blood flow to the left lung remains durable.
The most common surgical procedure involves dividing the anomalous left pulmonary artery at its origin from the right pulmonary artery. The surgeon then moves the vessel to the front of the trachea and reattaches it to the main pulmonary artery. This re-implantation places the artery in its correct anatomical position, relieving the compression on the airway. The procedure is performed through an incision in the chest, and the patient is placed on a heart-lung bypass machine during the repair.
In many cases, the patient also has associated tracheal stenosis. When this is present, a second procedure called a slide tracheoplasty may be performed during the same operation. This airway reconstruction involves making incisions in the narrowed segment of the trachea and sliding the two pieces together to create a wider, more stable airway. Combining the arterial re-implantation with the tracheal repair addresses both issues in a single surgical event.
Recovery and Long-Term Outlook
Following surgery, the infant is transferred to a pediatric intensive care unit (ICU) for close monitoring. The post-operative period often requires mechanical ventilation to support breathing while the airway heals and the lungs recover. The length of the ICU stay can vary depending on the complexity of the surgery, particularly if a tracheal repair was also performed. Patients who required ICU care before their surgery may face a higher likelihood of future interventions.
The long-term prognosis after a successful LPAS repair is very good. The survival rate for isolated LPAS repair is high. However, the outlook can be more complex for children who required simultaneous repair of intracardiac defects or severe tracheal stenosis, with survival rates being lower in these groups.
Long-term follow-up care is a part of post-operative management. Patients will have regular appointments with cardiology and pulmonology specialists to monitor their progress. These check-ups involve imaging studies to ensure the reimplanted artery remains open and that blood flow to the left lung is adequate. Follow-up is also needed to monitor for any residual narrowing of the airway, especially in children who underwent tracheal reconstruction.