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MMCTS
(January 23, 2009). doi:10.1510/mmcts.2008.003343 Copyright © 2009 European Association for Cardio-thoracic Surgery Procedure Pulmonary artery sling with tracheal stenosis ka*Department of Pediatric Cardiac Surgery, German Pediatric Heart Centre, Asklepios Clinic Sankt Augustin, Arnold Janssen Str. 29, 53757 Sankt Augustin, Germany * Corresponding author: Tel.: +49 2241-249 603; fax: +49 2241-249 602 v.hraska{at}asklepios.com
Pulmonary artery sling (PAS) is a rare congenital heart disease in which the left pulmonary artery (LPA) originates from the right pulmonary artery (RPA) and encircles the distal trachea and right mainstem bronchus as it courses between the trachea and esophagus. Typically, patients with PAS have some respiratory symptoms, either due to external tracheal compression that can be corrected by relief of the sling mechanism, or due to severe diffuse tracheal stenosis with complete rings (ring-sling complex). The diagnosis of PAS is optimally made by echocardiography, while bronchoscopy is the key to the assessment of tracheal stenosis. Diagnosis is indication for surgery. Repair using a strategy of median sternotomy, cardiopulmonary bypass, division of the LPA and reimplantation into the main pulmonary artery (MPA), and simultaneous tracheal repair takes preference. Tracheal repair should be considered only in clinically symptomatic patients. The techniques of free tracheal autograft plasty or slide tracheoplasty offer promising results, and the choice of tracheal reconstruction should be guided by the clinical experience of the surgeon. Coexisting intracardiac pathologies are repaired at the same time. Postoperative care requires close multidisciplinary effort to achieve the best long-term result.
Key Words: Congenital heart disease • Pulmonary artery sling • Ring-sling complex • Tracheal stenosis • Vascular ring
Pulmonary artery sling (PAS) is a rare congenital condition in which the left pulmonary artery (LPA) originates from the right pulmonary artery (RPA) and encircles the distal trachea and right mainstem bronchus as it courses between the trachea and esophagus to reach the hilum of the left lung [1]. The ligamentum arteriosum or the ductus arteriosus originates from the main pulmonary artery (MPA), and passes anteriorly and superior to the left mainstem bronchus to join the descending thoracic aorta to complete the vascular ring [2, 3]. The clinical outcome of patients with PAS depends on the associated tracheal lesions and complex cardiac anomalies. Coexisting diffuse tracheal stenosis, creating a ring-sling complex, is identified in up to 65% of patients with PAS [4]. Typically, stenosis of the trachea is due to complete tracheal rings and ranges from a profound degree of hypoplasia of the entire tracheobronchial tree to a discrete stenosis. Interestingly, despite compression of the tracheobronchial tree by the sling, tracheomalacia is usually not a feature. Congenital heart defects are found in 50% of PAS cases, the most common being atrial and ventricular septal defects, patent ductus arteriosus, left superior vena cava, and tetralogy of Fallot [5].
Current treatment protocol
Repair of PAS with resection of the trachea and closure of the VSD in an infant In this specific symptomatic infant, the diagnosis was established by ECHO and confirmed by angiography and tracheography (Video 1). Intraoperative bronchoscopy demonstrated short-segment tracheal stenosis with complete tracheal rings involving the distal part of the trachea.
Median sternotomy is performed. The thymus is completely resected, and the pericardium is harvested, and pretreated in glutaraldehyde for further use. The aorta and the pulmonary artery are dissected free, and the ductus arteriosus (or ligamentum) is ligated and divided. The LPA is identified as originating from the superior aspect of the RPA (Video 2).
Exposure of the stenotic trachea is performed by dissecting the space between the aorta and superior vena cava (SVC) (Videos 3 and 4).
CPB is commenced (Video 5). Being on CPB provides complete freedom to manipulate the pulmonary arteries and respiratory support for the tracheal repair. During this time frame the endotracheal tube might be removed, and then either rigid or fiberoptic bronchoscopy is performed to confirm the extent and degree of stenosis. Needles can be placed through the trachea, using bronchoscopic visualization, to delineate the extent of stenosis externally.
During cooling, the stenotic segment of the trachea is transected (Video 6). The short segment stenosis of the trachea (in this case 4 rings) is resected (Video 7).
Subsequently, the LPA is translocated anterior to the trachea, and the trachea is reconstructed (Video 8).
Intraoperative bronchoscopy is then performed to assess the repair and confirm airway patency. The pericardial flap created is used to wrap the tracheal anastomosis. Subsequently, the endotracheal tube is reinserted and the tracheal airway pressure is temporarily increased to confirm an airtight anastomosis (Video 9).
The possibility of kinking of the LPA and compression of the trachea by the LPA are evaluated. Usually the takeoff of the LPA is at an angle of nearly 180°, and that may cause proximal kinking. The decision is made in favor of translocation of the LPA (Video 10).
The aorta is cross-clamped, and the heart is arrested with crystalloid cardioplegia. Working through the tricuspid valve, the ventricular septal defect is closed with the patch using a continuous suture technique (Video 11).
The LPA is transected and anastomosed to the opening created in the MPA at a site that approximates the usual anatomic configuration. The opening in the RPA is closed with a running suture (Video 12).
After rewarming, the patient is weaned from bypass and the final outcome of the operation is evaluated (Video 13).
The strategy of median sternotomy, CPB, and LPA division and reimplantation into the MPA, with simultaneous tracheal repair and repair of intracardiac anomalies, provides encouraging results. Using the reimplantation technique, early mortality in repair of the PAS alone approaches zero, with a 100% LPA patency rate [3, 5]. Results of the repair of short segment tracheal stenosis using resection and end-to-end anastomosis are excellent [5, 8, 9, 10]. Surgical repair of long-segment congenital tracheal stenosis exhibits higher mortality and morbidity rates. Improved results were achieved with the use of the slide tracheoplasty and the free tracheal autograft technique (Table 1).
Virtually all patients with PAS have some respiratory symptoms, either due to external tracheal compression that can be corrected by relief of the sling mechanism, or due to severe diffuse tracheal stenosis with complete rings (ring-sling complex) [4]. Currently there is agreement about methods of establishing the diagnosis and sling surgery. The controversy persists regarding the optimal management strategy of long-segment congenital tracheal stenosis [3, 5, 6, 7].
Clincal status and diagnosis
Surgical considerations of the pulmonary artery sling repair The reimplantation technique [3, 5] takes preference over translocation [8] with distal tracheal resection. There are concerns about translocation, such as the possibility of LPA kinking and anterior compression of the trachea by the LPA [5, 16] (Video 10). In addition, translocation could result in compression of the LPA against the trachea, with a risk of LPA occlusion [16]. Several reports have described excellent long-term patency of implanted left pulmonary arteries [3, 5, 15].
Surgical considerations of tracheal reconstructions If tracheal surgery is indicated, the perioperative bronchoscopy is essential to precisely define the degree and length of tracheal stenosis, as the extent of stenosis is not always apparent when viewing the trachea externally. If the stenosed segment is short, it is best treated with resection and end-to-end anastomosis. Resection is generally applied when a stenosis involves <30% to 40% (<8 rings) of the total tracheal length; otherwise excessive anastomotic tension might lead to recurrent stenosis or fatal separation [3, 5, 6, 8, 9, 10]. For patients with long segment congenital tracheal stenosis (>8 rings) several surgical techniques have been suggested, but the optimal approach remains controversial. These techniques include rib cartilage tracheoplasty, pericardial patch tracheoplasty, tracheal autograft plasty, and slide tracheoplasty. The primary concerns include the growth potential of the reconstructed trachea, the incidence of early and late granulation tissue at the repair site, and the long-term functional outcome [3, 5]. Good results were reported with pericardium and with rib cartilage grafts for tracheal repair [5, 6]. Autologous pericardial patch tracheoplasty has the advantage that minimal dissection is required to expose the anterior trachea, thus preserving the lateral blood supply. The pericardial patch is simple to construct, and it can enlarge the entire trachea [6]. The major disadvantage is the potential for patch collapse, the need for prolonged periods of paralysis with ventilatory support, and the formation of obstructing granulation tissue along the suture line that requires repeated endoscopic laser resection [3]. The frequency of postoperative complications requiring reoperation, especially in the presence of pulmonary artery sling, is as high as 50% [5]. The main advantage of the rib cartilage graft technique is its rigidity, which allows the avoidance of prolonged postoperative airway splinting by the endotracheal tube, in contrast to the pericardial patch technique, in which airway splinting is mandatory [18]. However, it is not easy to achieve an airtight suture line using this rigid material. Favorable results for rib cartilage tracheoplasty, with a low rate of postoperative problems and without operative mortality, have been demonstrated [18]. Development of troublesome granulation tissue is frequent [6, 19]. Several surgeons [3, 11, 12, 13, 14, 15, 19] have supported the superiority of slide tracheoplasty for long segment stenosis. Slide tracheoplasty doubles the circumference of the trachea, creating a nearly four-fold increase in cross-sectional area. The advantages of this technique are the avoidance of graft materials, tension-free sutures, anatomic and functional trachea, and shorter intensive care unit or hospital stay. Since the trachea is lined with normal ciliated tracheal epithelium, there is little tendency to develop granulation tissue. This technique is even suitable for infants with long-segment tracheal stenosis [3, 15, 19]. For slide tracheoplasty, satisfactory subsequent growth has been experimentally and clinically demonstrated [19]. Excellent results for infants with long segment congenital tracheal stenosis were reported with the free tracheal autograft technique [6, 7]. This technique uses only autologous material for the repair. It is technically easy to perform and is architecturally sound; the autograft is already lined with respiratory epithelium; the cartilage intrinsically maintains its contour; there is potential for growth, and it is readily available. If necessary, this technique can be combined with pericardial augmentation [6].
Repair using a strategy of median sternotomy, CPB, division of the LPA and reimplantation into the MPA, and simultaneous tracheal repair is preferable. However, only patients with significant respiratory symptoms should be considered for simultaneous repair of complete tracheal rings. Symptoms are a more important factor than the degree of stenosis itself, when deciding whether to perform tracheal surgery. The choice of tracheal reconstruction should be guided by the clinical experience of the surgeon. Coexisting intracardiac pathology should be repaired at the same time.
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