Pulmonary artery (PA) sling is an uncommon form of vascular ring, which results from an aberrant division of the main PA. PA slings may produce a combination of symptoms related to focal compression of the airway or esophagus with diagnosis of the condition typically made in childhood. Rarely, adult presentations with symptoms of dysphagia have been reported. We present a case of PA sling in the adult resulting in focal tracheomalacia and significant respiratory symptoms.
A 29-year-old woman experienced acute onset of severe dyspnea, intractable “barking” cough, and wheezing after the cesarean section delivery of her third child. She had a history of seasonal pollen allergies and quiescent asthma, diagnosed in childhood and treated with inhaled steroids, and a life-long pattern of exertional dyspnea attributed to the same. She had a 20 pack-year smoking history, but was a nonsmoker for 10 years. She denied recent travel or other exposures and had no similar problems after the birth of her first 2 children, also by cesarean section.
The patient was treated with bronchodilators and oral corticosteroids without improvement. Chest radiography revealed no specific abnormality, and subsequent bronchoscopy with bronchoalveolar lavage was positive for Klebsiella pneumoniae (>10,000 colonies). Despite an appropriate antiinfective regimen, she had persistent cough and exertional dyspnea, limiting activity. IgE levels were normal and Aspergillus-specific antigens ANCA and CRP were all negative, arguing against vasculitis or allergic etiology. Pulmonary function testing demonstrated a mild restrictive pattern. Chest computed tomographic scan without contrast showed narrowing of the distal trachea pertaining to focal malacia and the patient was referred to our institution for further evaluation.
Following a standard protocol for the evaluation of tracheobronchomalacia, she underwent a dynamic airway computed tomography with images acquired during both inspiration and expiration. This study identified a PA sling, resulting in extrinsic compression and collapse of the membranous wall of the distal trachea and proximal left mainstem bronchus (Fig. 1). Dynamic flexible bronchoscopy revealed a pulsatile extraluminal mass causing extrinsic airway compression, without complete tracheal rings or areas of fixed stenosis (Fig. 2). A magnetic resonance angiography study was carried out to further delineate the vascular anatomy (Fig. 3). The anomalous left PA originated from the proximal right PA, passing between the trachea and esophagus and compressing the distal trachea. Surgical resection of the vascular sling was accomplished with reanastomosis to the main PA through median sternotomy on cardiopulmonary bypass. No airway reconstruction was required. She recovered well, with complete resolution of respiratory symptoms.
Vascular rings are unusual congenital anomalies that occur early in the development of the aortic arch and great vessels. Symptoms associated with vascular rings relate to the structures that are encircled by the ring, mainly the trachea and esophagus. These anomalies are uncommon, accounting for <1% of congenital cardiac defects. The 2 most common forms are the double aortic arch and the right aortic arch with a left ligamentum arteriosum, accounting for 85% of cases.1–3 The anomalous left PA, or PA sling, accounts for approximately 10% of cases.
PA sling was first described at autopsy by Laevecke in 1897.4 Symptoms range from absent-to-severe respiratory distress, with airway symptoms predominating in infants, whereas dysphagia may be the primary complaint of older patients.5 The 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. A strong embryologic association exists between PA slings and development of complete tracheal rings, accentuating tracheal stenosis.6
Surgical repair is focused on restoration of the normal anatomic relationship between the airway and pulmonary vasculature. Exposure is obtained by median sternotomy, typically under cardiopulmonary bypass.7 The left PA is disconnected from the right PA trunk and anastomosed to the proximal main PA. Careful examination of the trachea is required as >50% of patients have associated severe tracheobronchial anomalies such as tracheomalacia, stenosis, webs, or complete tracheal rings. In the presence of complete tracheal rings and concomitant tracheal stenosis, segmental resection and reconstruction by slide tracheoplasty are often necessitated.5 Routine preoperative transthoracic echocardiography is recommended to exclude associated congenital heart defects, which are present in approximately 10% to 15% of the cases.5
Adult presentation of PA sling is rare, with only 22 reported in the literature. Of these, only 1 patient required surgical correction for symptoms of dysphagia.8 This is the first report of the need for surgical correction of a PA sling in adulthood due to respiratory symptoms. Interestingly, the sharp anterior angulation of the anomalous left PA resulted in compression of the distal trachea and proximal left mainstem bronchus in our patient, rather than the typical right-sided compression, although it is unclear whether this conformation affected the severity of respiratory symptoms. Although rarely required, this case demonstrates that isolated surgical correction of PA sling in an adult can ameliorate respiratory symptoms secondary to focal tracheomalacia, even without airway reconstruction.
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