INTRODUCTION: Pulmonary artery sling is a congenital vascular anomaly in which the pulmonary arterial circulation to the lung arises from the pulmonary artery (PA) of the contralateral lung rather than a mainstem PA. Tracheal compression occurs as the anomalous pulmonary artery traverses the mediastinum posterior to the airway. This anomaly, while often seen in children, rarely remains undiagnosed into adulthood. We describe a case of PA sling presenting with respiratory symptoms in an adult.
CASE PRESENTATION: A 29 year old female developed severe dyspnea, cough and wheezing following caesarean section for the delivery of her third child. She had a history of quiescent asthma and seasonal allergies. The patient resides in a rented house with some mold, but endorses no recent travel or exposure history. She was treated with empiric corticosteroids and underwent bronchoscopy for broncho-alveolar lavage. Cultures grew Klebsiella and she was treated with a course of antibiotic therapy. Despite an appropriate anti-infective regimen, her symptoms worsened, with a persistent ‘barking’ cough and exertional dyspnea with exercise limitation. She underwent thorough allergy testing which revealed allergy to grasses, trees and mold. However, IgE levels, aspergillus specific antigens, ANCA and CRP were all negative, arguing against chronic allergic reaction, allergic broncopulmonary aspergillosis or Churg-Strauss vasulitis. A repeat dynamic bronchoscopy was performed to assess for a possible component of tracheobronchial malacia. This study revealed a focal collapse in the membranous wall of the distal trachea and proximal left mainstem bronchus. An airway computed tomography scan identified a vascular sling. The anomalous left PA originates from the proximal right PA then passes between the trachea and esophagus, resulting in extrinsic compression of the distal trachea. The patient underwent surgical resection of the vascular sling with re-anastomosis to the main PA. She has recovered well without persistent respiratory symptoms.
DISCUSSIONS: Vascular rings are rare and usually diagnosed early in life. Symptoms range from absent to significant respiratory distress, especially in the newborn. Airway symptoms predominate early in life while dysphagia may be the primary symptom in older patients. PA slings are among the least common of the vascular rings, comprising only 10% of diagnosed cases in large series (insert ref from CMH series here). This anomaly is created by formation of the left PA from the right sixth vascular arch (rather than the left), resulting in a left PA arising from the posterior aspect of the right PA. There is also a strong embryologic association between pulmonary artery sling and development of complete tracheal rings, accentuating the tracheal stenosis. Surgical repair is focused on the restoration of the normal anatomic relationship between the airway and pulmonary vasculature. Exposure is obtained by median sternotomy and cardiopulmonary bypass is usually required. The left PA is disconnected from the right and anastomosed to the proximal main PA. Careful examination of the trachea is required as segmental resection and reconstruction by slide tracheoplasty is often required due to the significant airway stenosis which often accompanies these anomalies (1). Routine transthoracic echocardiography is recommended to exclude associated congenital heart defects (2).
CONCLUSION: Diagnosis of vascular rings requires a high index of suspicion with typical symptoms of noisy breathing and respiratory distress. CT imaging with contrast is the preferred diagnostic modality to indentify the anomaly and define the anatomy. Surgical correction is the treatment of choice, often requiring tracheal reconstruction. The rare presentation of our patient in adulthood illustrates the spectrum of age and delay in symptoms that are possible.
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