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Ann Thorac Surg 1999;68:989-994
© 1999 The Society of Thoracic Surgeons
a Herzzentrum, University of Leipzig, Leipzig, Germany
Address reprint requests to Dr van Son, Herzzentrum, University of Leipzig, Russenstrasse 19, D-04289, Leipzig, Germany
| Abstract |
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Methods. Five symptomatic infants (3 boys and 2 girls; median age 5 months; range, 3 weeks to 11 months) with pulmonary artery sling were operated on through a median sternotomy with aid of cardiopulmonary bypass. In 3 patients, the left pulmonary artery was transected from the right pulmonary artery and implanted into the main pulmonary artery. In addition, the anterior trachea was augmented with a pericardial patch (n = 2). In the remaining 2 patients, associated tracheal stenosis was resected, the left pulmonary artery was translocated anterior to the trachea, and the trachea was reconstructed.
Results. All 5 infants survived the operation. The 3 patients in whom the left pulmonary artery was implanted into the main pulmonary artery had an uncomplicated postoperative course. All 3 patients, at a follow-up of 10 months to 7.9 years, were free of symptoms; the left pulmonary artery was documented to be widely patent. The remaining 2 patients in whom the left pulmonary artery was translocated anterior to the trachea could not be extubated. In both patients the distal trachea was compressed anteriorly by the left pulmonary artery. One of these patients died at 1 week postoperatively secondary to tracheal dehiscence. In the other patient, the left pulmonary artery was implanted into the main pulmonary artery with good result; at a follow-up of 3.9 years, mild residual stridor has persisted.
Conclusions. In pulmonary artery sling, implantation of the aberrant left pulmonary artery into the main pulmonary artery, if necessary combined with anterior tracheoplasty, reliably eliminates tracheal and esophageal compression and maintains antegrade flow into the left pulmonary artery. Translocation of the left pulmonary artery anterior to the trachea without implanting it into the main pulmonary artery is not favored because that might result in anterior compression of the trachea. In addition, we are concerned about growth of the circumferential tracheal anastomosis in neonates and infants.
| Introduction |
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Most patients with PAS have clinical symptoms secondary to tracheal compression and, to a lesser degree, esophageal compression [214]. The most common presentation consists of wheezing and stridor, often with prolongation of the expiratory phase. Pneumonitis, atelectasis, or emphysema of the lung might be present, secondary to compression of either main bronchus (right more than left). Acute episodes of dyspnea and cyanosis are common and can result in unconsciousness, convulsions, or even death. Usually, symptoms present in neonates or infants. Failure to recognize a symptomatic PAS results in a high likelihood of death, usually during the first year of life [4, 7].
Potts and colleagues [15] first reported successful reconstruction of this anomaly. The evolution of their technique resulted in the currently most applied technique, namely, detachment of the aberrant LPA, translocation of the vessel to the left of the trachea, and its implantation into the main pulmonary artery [16]. To address the problem of structural tracheal stenosis, Jonas and associates [14] resected the stenosed tracheal segment, translocated the LPA anterior to the trachea (without implanting it into the main pulmonary artery), and reconstructed the trachea. We review our experience with PAS, which includes both operative techniques.
In PAS the LPA originates extrapericardially from the posterosuperior aspect of the right pulmonary artery (Fig 1). The right pulmonary artery is a direct extension of the main pulmonary artery. The LPA is considerably smaller than the right pulmonary artery. It curves upward and backward over the proximal right main bronchus and then to the left behind the trachea, the carina, and the left main bronchus, thereby indenting these structures and displacing the distal trachea and carina toward the left. The right main bronchus is usually compressed anteriorly. The LPA passes in front of the esophagus, which is usually indented across its entire anterior aspect or less often on its leftward anterior surface only [4, 7]. The ligamentum arteriosum (or ductus arteriosus) originates from the point of origin of the right pulmonary artery, passes backward superior to the left main bronchus and the anomalous LPA, and connects to the descending aorta. It usually participates in forming a vascular ring around the trachea.
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| Patients and methods |
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Of the remaining 2 patients with PAS, one had associated tetralogy of Fallot with a moderate short-segment stenosis of the trachea, and the other had a stovepipe trachea. In both patients, the ligamentum arteriosum was divided and 2 or 3 tracheal rings were resected, respectively. Subsequently, the LPA was translocated anterior to the trachea, and the trachea was reconstructed with a continuous 6-0 polyglyconate suture, thereby avoiding the placement of suture material in the tracheal mucosa (Fig 3). In addition, in the first patient, associated tetralogy of Fallot was repaired. Intraoperative bronchoscopy verified an adequate luminal diameter of the trachea in both patients and absence of anterior compression of the trachea. In the patient with stovepipe trachea there was mild residual posterior tracheomalacia.
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| Results |
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Both patients in whom the LPA was translocated without implanting it into the main pulmonary artery could not be extubated. The patient with a stovepipe trachea, after an initially uncomplicated postoperative course, developed tracheal dehiscence on the fifth postoperative day. He died 2 days later secondary to sepsis. At autopsy the tracheal anastomosis was dehiscent at the anterior suture line, which was compressed by the proximal LPA. The second patient, in whom associated tetralogy of Fallot had also been repaired, could not be extubated because of clinical evidence of airway obstruction. Bronchoscopy after 12 days of ventilatory support demonstrated a pulsatile anterior indentation of the distal trachea. At reoperation, the tracheal anastomosis was found to be intact. The anterior aspect of the distal trachea, however, was compressed by the proximal segment of the anomalously coursing LPA (Fig 3). Without the use of cardiopulmonary bypass, the right pulmonary artery was partially clamped at the origin of the anomalous LPA, the LPA was detached from the right pulmonary artery, the right pulmonary artery was oversewn, and the LPA was shortened and implanted into the left side of the main pulmonary artery using a continuous 6-0 polyglyconate suture (Fig 4). After an additional 9 days of ventilatory support, the patient was weaned off the ventilator. At a follow-up of 3.9 years, residual mild stridor has persisted in this patient. Bronchoscopically there was mild tracheomalacia immediately proximal to the tracheal anastomosis with a moderate stenosis at the site of the tracheal anastomosis. Echocardiography demonstrated a patent LPA.
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| Comment |
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Several surgical strategies for repair of PAS have evolved during the past 4 decades, which vary in approach (left thoracotomy versus median sternotomy); technique of repair of the LPA, the trachea, or both; use versus nonuse of cardiopulmonary bypass; and type of suture material (absorbable versus nonabsorbable) [2, 5, 816]. The classic repair of PAS consists of detachment of the LPA, translocation of the vessel to the left of the trachea, and implantation of it into the main pulmonary artery [16]. Although this operation traditionally has been done through a left thoracotomy, we prefer a median sternotomy because it allows more precise and thorough dissection and mobilization of the main pulmonary artery, the right pulmonary artery, the LPA, and the trachea. Mobilization of these structures decreases the potential for tension on the anastomosis between the LPA and the main pulmonary artery. In addition, with aid of cardiopulmonary bypass, associated tracheal stenosis can be corrected. Pawade and coworkers [9] treated 18 patients with PAS in whom the anomalous LPA was implanted into the main pulmonary artery. One patient (6%) died late. The LPA was patent in all 14 patients investigated postoperatively. Two of the 4 patients with stovepipe trachea, all of whom had tracheal resection with end-to-end anastomosis, had residual tracheal stenosis with recurrent respiratory infections. Backer and associates [11] treated 12 patients in whom the anomalous LPA was implanted into the main pulmonary artery, with no early deaths. Two patients (17%) died late after tracheoplasty because of extensive narrowing of the trachea from complete tracheal rings. On the basis of these reports and our own experience, we believe that implantation of the anomalous LPA into the main pulmonary artery with the aid of cardiopulmonary bypass is an effective operation for treatment of symptomatic PAS because it reliably eliminates tracheal and esophageal compression and maintains antegrade flow in the LPA. It is important to shorten the LPA to avoid redundancy of the vessel and its potential complications, such as kinking and lateral compression of the trachea or left main bronchus. To facilitate growth of the translocated LPA, we use a fine absorbable suture.
In our opinion tracheal stenosis should be treated surgically only in the presence of severe obstruction. The presence of complete tracheal rings per se is not an indication for tracheoplasty. Generally, stenosis of the trachea in the neonate or infant does not become critical until the minimal diameter is less than 2 mm. Although there is a direct relationship between the length of the stenotic segment and airway resistance, the relationship to luminal diameter is to the fourth power. This relationship should be the overriding factor in determining the need for tracheoplasty. The course of most airway problems, such as tracheomalacia and mild to moderate compression from a vascular structure, is improvement with age, especially if compression by the aberrant LPA or other type of vascular ring is resolved surgically. For these reasons we believe that conservative treatment is preferable in mild or moderate tracheal stenosis. In case of severe short-segment tracheal stenosis or stovepipe trachea, a tracheoplasty using pericardium or a section of rib cartilage as an augmentation patch onto the anterior surface of the trachea has had excellent results [2124]. We believe that suspension of the tracheal augmentation patch to the surrounding mediastinal tissues with sutures is important to prevent prolapse of the pliable patch into the tracheal lumen during inspiration. The advantage of the anterior tracheoplasty technique, as opposed to tracheal resection and end-to-end anastomosis, is the avoidance of a circumferential tracheal anastomosis with limited tendency for growth [9, 2124]. In addition, there is no limitation on the length or location of the stenosis (such as extension of the stenosis into the left or right main bronchus) that needs to be repaired. Despite the encouraging results using pericardium or rib cartilage for augmentation of the trachea, remaining concerns regarding these techniques include the growth potential of the reconstructed trachea, the incidence of late granulation tissue growth at the repair site, the fate of the luminal surface of the patch, and the long-term outcomes of the various types of repair. Although the novel technique of slide tracheoplasty can be an excellent technique for augmentation of the tracheal lumen in older children and adults [25, 26], the feasibility of this technique in neonates and infants and the growth potential of the long suture line remain to be determined.
Jonas and associates [14] reported an alternative technique for repair of PAS, consisting of partial resection of the trachea at the level of the LPA, translocation of the LPA anterior to the trachea, and end-to-end tracheal reconstruction. Castañeda and colleagues [13] reported use of this technique in 5 patients with PAS, in 2 of whom this procedure resulted in kinking of the proximal LPA, necessitating implantation of this vessel into the main pulmonary artery. One patient with absence of the right lung and other extracardiac anomalies died (20%). For the following reasons we do not favor translocation of the LPA anterior to the trachea: (1) in the presence of mild to moderate tracheal obstruction there might be no need for tracheal resection; (2) in the presence of marked tracheal stenosis we favor an anterior tracheoplasty as opposed to tracheal resection with end-to-end anastomosis for the reasons outlined earlier; and (3) translocation of the LPA could convert compression of the right main bronchus or posterior compression of the trachea into anterior compression of the trachea or left main bronchus. This phenomenon was observed in both patients in this series in whom this technique was applied. Such potential for anterior compression of the trachea, often superimposed upon tracheomalacia of the distal trachea, may be most explicit in patients who undergo concomitant repair of obstructive lesions of the right heart (such as pulmonary stenosis or tetralogy of Fallot). Increased pulmonary arterial blood flow postoperatively could exacerbate anterior compression of the trachea. In addition, because the origin and proximal course of the LPA is left intact, this operation could result in compression of the LPA against the trachea with the potential for occlusion of this vessel [11].
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