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ORIGINAL CONTRIBUTION |
Department of Cardiac Surgery, Royal Hospital for Sick Children, Scotland, UK
For reprint information contact: James Pollock, FRCS Tel: 44 141 201 0269 Fax: 44 141 201 9204 Email: jim.pollock{at}yorkhill.scot.nhs.uk, Department of Cardiac Surgery, Royal Hospital for Sick Children, Dalnair Street, Glasgow G3 8SJ, Scotland, UK.
| ABSTRACT |
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| INTRODUCTION |
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| PATIENTS AND METHODS |
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Table 3
lists the associated cardiac and non-cardiac anomalies.
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Cardiopulmonary bypass was used for simultaneous correction of an associated intracardiac malformation in 2 patients ventricular septal defect (VSD) with atrial septal defect (ASD) and patent ductus arteriosus (PDA) in 1 patient, and VSD and anomalous origin of the left coronary artery from the pulmonary artery in the other. Concurrent coarctation repair was performed in 1 child. Four patients underwent an aortopexy, in addition to arch division.
All survivors had 6 monthly reviews for 2 years and then yearly. Follow-up data from 6 months to 16 years (mean 7.1 years) were available for 28 patients. For patients with persistent respiratory symptoms and those with a history of obstructive pulmonary disease, pulmonary function tests were obtained.
| RESULTS |
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Complete symptom resolution occurred in 22/29 patients (75.9%) and partial improvement in 6 patients (persistent wheeze, 3; stridor, 3). The 3 asthmatic children continued to be symptomatic. All 3 patients who had residual stridor had preoperative tracheomalacia. Patients with partial improvement (bronchial asthma, 3; residual stridor, 3) were submitted to lung function tests. Those with asthma had abnormal flow volume loops indicative of significant central airway obstruction; others had normal studies.
Of the 9 patients with tracheomalacia, 3 (33.3%) had residual stridor while 5 (55.6%) had complete resolution. On serial follow-up, all 3 patients with residual stridor improved over time, and no further surgery was required.
| DISCUSSION |
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One patient had a DiGeorge syndrome, and 1 had a VACTERL (Vertebral, Anal, Cardiovascular, Tracheo-Esophageal, Renal, and Limb) association. Brzezinska-Kolarz et al3 reported familial recurrence of DAA, supporting a genetic etiology. Cytogenetic examination of their patients disclosed pericentric inversion of chromosome 9. Symptomatic tracheobronchial compression varies inversely with the severity of compression.4 Tracheal compression causes airflow obstruction and decreased mucociliary clearance of secretions, leading to recurrent bronchopulmonary infections.4 Reflex apnea is hypothesized to be a type of respiratory arrest that occurs when vagal afferent nerves are stimulated. Esophageal compression by the DAA causes it to bulge forward, indenting the membranous trachea and exacerbating respiratory distress. Esophageal compression also leads to regurgitation and aspiration pneumonia.4
The ascending aorta divides into two arches, which encircle the trachea and the esophagus and join posteriorly to form the DTA. The right arch gives rise to the right carotid and right subclavian arteries. The left carotid and left subclavian arteries arise from the left anterior arch (Figure 1
). Both arches may be patent, or an atretic segment may exist at any location on either arch.
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This is important to plan the site of operative division of the vascular ring.
In patients with left arch dominance, the minor right arch typically is patent. More commonly, the DTA is on the left side rather than the right. In patients with a right DTA, the arches are right anterior and left posterior. Of the 4 patients who had right DTAs in our series, 2 had codominant arches and 2 had left arch dominance. Tracheobronchial anomalies,7 found in patients with DAAs include severe dyskinesia, tracheomalacia (9 patients in our series) or tracheobronchial hypoplasia.
The most frequently associated lesions are tetralogy, VSD, coarctation, PDA, and esophageal atresia. An undiagnosed arch may complicate repair of esophageal atresia.8 Two patients had repair of esophageal atresia prior to arch division. One patient also had a Nissens fundoplication for severe gastroesophageal reflux.
The severity of compression and the onset of symptoms are determined by the space between the tracheoesophageal axis and the components of the ring, and tracheoesophageal dimensions. Fleenor et al9 showed that patients with symptomatic vascular rings have significantly altered tracheal geometry. Patients with early symptoms of tracheal compression tend to have very tight rings, while those with loose rings present later in life. McLaughlin et al4 reported that only 34% were correctly diagnosed by 6 months of age. Apparent life-threatening events or death spells were present in 7 patients. Co-existent chronic pulmonary disease should be carefully documented as some patients may have persistent postoperative wheeze. We have found pre and postoperative lung function tests useful in such patients. Esophageal symptoms such as emesis, choking, or dysphagia predominate in older children and adults.
The chest radiograph establishes arch location. An ill-defined arch is often observed in patients with DAA.10 Lateral indentation of the tracheal air column may be revealed on frontal films (Figure 3A
). Lateral views are evaluated for retrotracheal opacity, anterior tracheal bowing, and posterior indentation.
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Barium esophagography reliably diagnosed a DAA in 19/20 patients in our series. Bilateral esophageal indentation (Figure 3B
) is observed on the anteroposterior view, forming a reverse S sign with the right-sided indentation being superior, while a posterior indentation is observed on the lateral view (Figure 3C
). However, the extant anatomy of a vascular ring that many authors think necessary for accurate preoperative planning, cannot always be delineated by esophagography. Doppler echocardiography depicts the great vessels, but structures without a lumen, such as a ligamentum arteriosum or an atretic arch, and compressed midline structures are difficult to identify. Fourteen patients in our series had echocardiograms; revealing associated intracardiac problems in 7 of them. Echocardiography was non-diagnostic in 4/14 patients.
Aortography provides detailed information but cannot distinguish between an atretic arch and complete interruption. It was used earlier in our series, but is no longer used solely for this indication.
Computed tomography (CT) reveals vascular, tracheobronchial (Figure 4A
), and esophageal anatomy. In patients with a DAA there are four separate brachiocephalic vessels (instead of the normal three) in the superior mediastinum grouped around the trachea. This is called the "four vessel" sign (Figure 4B
). Spiral CT (Figure 5
) provides images of even greater detail, especially for showing the dominant arch.11
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Achiron et al13 described a novel, sonographic approach for in-utero aortic arch evaluation. The normal left aortic arch was defined by the V-shaped appearance of the junction between the ductus arteriosus and aortic arch, with the trachea situated posteriorly. DAAs were diagnosed when the great vessels appeared U-shaped, with an intermediate location of the trachea.
Reported complications from unrepaired DAA include aortic dissection.14 McKeating et al15 reported fatal hematemesis due to erosion by a nasogastric tube into the right component of an unrecognized DAA.
Non-surgical management is variably effective for patients with loose vascular rings who are mildly symptomatic. Asymptomatic patients may become symptomatic when a respiratory infection supervenes and causes tracheal edema.11 Most patients however are symptomatic at presentation. An increased incidence of persistent postoperative symptoms, secondary to longstanding tracheal compression has been reported. We therefore recommend surgical division in all patients with DAA.
A left thoracotomy provides the best access to the middle and posterior mediastina in most patients, especially those with a dominant right arch. The recurrent laryngeal and vagus nerves are identified and avoided. Division of the smaller arch is performed while adequate flow in the arch vessels and the DTA are maintained. Simple ligation and division can cause ligature slippage and catastrophic hemorrhage. Aortopexy is necessary if the two ends of the divided ring do not spring apart naturally to relieve the compression.16 The threshold to perform aortopexy should be low, especially in those with preoperative tracheomalacia or laryngomalacia. The remnant arch is tacked to the anterior chest wall or the back of the sternum, by interrupted pledgetted mattress sutures through the adventitia of the vessel. Aortopexy is performed in conjunction with intraoperative bronchoscopy to confirm airway relief. The ligamentum arteriosum is always divided. The trachea and esophagus are freed from potentially constrictive bands and fibrous tissue. Closure of the mediastinal pleura is not performed to avoid adhesive scarring in the affected area around the trachea and esophagus. These mechanisms help to avoid residual tracheoesophageal narrowing and persistent symptoms. Tracheal damage due to excessive manipulation should be avoided since it can be fatal and will not be reversed immediately. When associated intracardiac anomalies require surgery through a median sternotomy, division of the double arch is performed during the same procedure.
Complications include bleeding, pleural effusion, and chylothorax. Chun et al17 reported a 10.3% incidence of chylothorax in their series of patients with vascular rings. Phrenic, vagus, or recurrent laryngeal nerve injury may occur. We previously reported18 two patients with respiratory distress due to persistent tracheomalacia despite vascular decompression. They subsequently underwent tracheal resection with symptomatic relief. Cardiopulmonary bypass can be a useful adjunct in these cases.
Video-assisted thoracoscopic surgery is applicable in patients with non-patent ring segments.19 The development of endoscopic vascular clamps will allow proximal and distal vascular control thereby extending the technique to patients with patent arches.
Tracheomalacia led to death in 1 patient and delayed extubation in 3. About 30% of patients may have persistent airway symptoms postoperatively. This may be related to tracheomalacia, persistent extrinsic airway compression or both. Other causes include an undivided ligamentum arteriosum and/or adhesive bands. In a series of 204 children with tracheoesophageal compression reported by Backer et al,10 almost 10% experienced residual tracheomalacia. These patients may benefit from an aortopexy, resection of a severely malacic tracheal segment or more complex tracheoplasty. Other techniques include tracheostomy, stenting, and external support devices. Fleck et al20 found two discrete patterns of airway narrowing and extrinsic compression in patients with persisting symptoms: (1) airway narrowing immediately abutting the intact arch; (2) narrowing of the left main bronchus; the DTA was in an abnormal midline position immediately anterior to the spine instead of being paraspinal. This leads to compression of the left main bronchus between the DTA posteriorly, and the pulmonary arteries anteriorly. Patients with DAA are prone to have midline DTAs related to the dual sidedness of their bilateral arches. This pattern of airway compression is independent of the dominant arch. Our current protocol is to evaluate patients with persistent airway symptoms with bronchoscopy and cross-sectional imaging like MRI or helical CT, to delineate extrinsic structures causing compression and to determine the airway caliber.
Based on our experience we stratified patients into three categories: (1) low risk DAA; (2A) intermediate risk DAA with chronic obstructive pulmonary disease; (2B) intermediate risk DAA with tracheomalacia; (3) high risk DAA with asthma and severe tracheobrochial abnormalities.
The rarity of these anomalies denies us sufficient numbers to draw strong conclusions. This is a retrospective study and consequently has limitations. Associated cardiovascular anomalies might have been confounding factors with respect to the respiratory complaints.
Early diagnosis and surgery are imperative to reduce the long-term sequelae of tracheobronchial compression in children. Symptoms may take longer to regress after repair in patients with longstanding preoperative symptoms. When associated cardiac lesions are present, cardiopulmonary bypass can be used to allow concomitant correction of both lesions. Postoperative care is uncomplicated, if no tracheal trauma is inflicted at surgery. Surgery affords excellent long-term resolution of symptoms. However, they may not be relieved immediately or completely, especially in those with tracheomalacia and co-existing obstructive pulmonary disease, and hence long-term follow-up is necessary.
| REFERENCES |
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This article has been cited by other articles:
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C. Iida, M. Shiota, and D. Hata Dying spell caused by vascular ring BMJ Case Reports, April 29, 2010; 2010(apr29_1): bcr1020092341 - bcr1020092341. [Full Text] |
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