Concerned over her extreme poor performance status and the risk for general anesthesia, surgical decompression of the vascular anomaly was not considered. Insertion of a SEMS was instead chosen. On January 8, 2002, insertion with a 12 × 20-mm proximal-released uncovered Ultraflex nitinol SEMS (Boston Scientific, Natick, MA) using a flexible bronchovideoscope (BF type P240, Olympus Corp., Tokyo, Japan) under fluoroscopic guidance was tried first. However, the SEMS was quickly ejected as a result of the elasticity of the stenotic bronchus proximally into the trachea on deployment. A second 12 × 40-mm Ultraflex was attempted with a similar outcome. Fortunately, the distal end of SEMS could be anchored to the segment of the stenosis and permitted us to finally place the SEMS in the proper position using biopsy forceps. The right lung expanded successfully after this procedure. On surveillance bronchoscopy 1 week later, complete expansion of the SEMS resumed the patency of the RMB (Fig. 1B). Concurrent with the regular use of bronchodilators, the improved respiratory status allowed her to undergo implantation of a ventricular–peritoneal shunt on January 18, 2002. Accompanied by the improvement of nutrition and relief of bronchospasm, her endotracheal tube was removed 4 weeks later. She was discharged from the ICU and remained well at 6-month follow up.
Tracheobronchial compression from congenital vascular anomalies is a rare but treatable cause of respiratory distress and cyanosis, frequently occurring in infants and neonates. 1,2 Well-known lesions include pulmonary artery sling, ring-sling complex, anomalous innominate artery, and dilated (aneurysmal) great arteries. Airway chondromalacia is a frequent complication of these lesions. Early diagnosis requires a high index of suspicion and a prompt, thorough clinical and radiologic evaluation. Magnetic resonance imaging, multiplanar reformatted image of CT angiography, and respiratory dynamic CT scan had been reported to be excellent aids in delineation of the pathoanatomy. 3–5 We report an adult patient in whom an anomalous right pulmonary artery caused a short-segment RMB stenosis, which had not been described in the previous literature. Abnormal embryologic differentiation of the right sixth branchial arch could have led to the anomaly. Abrupt rise of the pulmonary artery pressure during acute exacerbation of COPD aggravated the chronic dynamic compression of the RMB by the congenital vascular anomaly and weakening of the bronchial cartilage secondary to the aging and malnutrition, which finally led to the critical stenosis of the compressed airway segment and the delay-onset of respiratory insufficiency.
Surgical correction is usually indicated for vascular tracheobronchial compression syndromes with respiratory insufficiency. In inoperable patients or those who decline surgery, internal stenting of the airway is an alternative. Insertion of a silicone stent necessitates rigid bronchoscopy under general anesthesia, which was risky in our patient. Lack of sufficient radial expansion force also precluded its use under the situation. Easy migration and mucus plugging were the other considerations. Endoscopic placement of expandable metallic stents, Gianturco Z stent (Cook Group Europe, Bjaeverskoo, Denmark) and Wallstent (Schneider Inc., Minneapolis, MN) had been reported sporadically for relief of tracheobronchial obstruction caused by vascular anomalies in infants. 6–8 However, the long-term outcome of the metallic stents in the pediatric population is currently unknown. Even for the expandable stents, the maximum expandable diameter might not be large enough to ensure the patency in adult life. The high pressures exerted by the Gianturco Z stent over the airway mucosa could lead to mucosa ischemia and perforation, which is dangerous when the extrinsic compression is vascular in origin (eg, aneurysm). 9
The newer SEMS, Ultraflex, made from single-strand nickel–titanium (nitinol) alloy, exhibits properties of “shape memory.”10 In stress–strain tests of all materials currently in use for tracheobronchial stenting, only nitinol shows a hysteresis curve that is very similar to elastic tissue such as cartilages. It exerts a constant, uniform radial pressure at the force required to maintain patency while minimizing traumatic tissue compression. Unlike the Wallstent, its looped ends provide an atraumatic interface with the mucosa, which could reduce the formation of granulation tissue. Grasping the knots over it with biopsy forceps also allows us to reposition the stent after deployment, like in our patient.
To our knowledge, this is the first patient who underwent insertion of Ultraflex for the extrinsic bronchial compression of vascular origin in adulthood in the literature. With adequate follow up, such a novel use of SEMS seemed to hold promise. Freedom from obstructive symptoms, liberation from a mechanical ventilator, and reduction in the duration of ICU stay justified the use of this approach. Similar to the few published reports of experience with this stent, longer follow-up evaluation is needed to determine the eventual tissue tolerance.
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Keywords:© 2003 Lippincott Williams & Wilkins, Inc.
adult; airway compression; bronchoscopy; pulmonary artery; stents