Original Report. Imaging Findings in Pediatric Patients with Persistent Airway Symptoms After Surgery for Double Aortic Arch

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1 Robert J. Fleck 1,2 Preeyacha Pacharn 1,3 Bradley L. Fricke 1 Matthew A. Ziegler 1 Robin T. Cotton 4 Lane F. Donnelly 1 Received August 30, 2001; accepted after revision October 22, Department of Radiology, Children s Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH Address correspondence to L. F. Donnelly. 2 Present address: Department of Radiology, Naval Medical Center, San Diego, CA Present address: Department of Radiology, Mahidol University, Bangkok, Thailand Division of Otolaryngology, Children s Hospital Medical Center, Cincinnati, OH AJR 2002;178: X/02/ American Roentgen Ray Society Original Report Imaging Findings in Pediatric Patients with Persistent Airway Symptoms After Surgery for Double Aortic Arch OBJECTIVE. The purpose of this study was to review the imaging findings of children referred for cross-sectional imaging to evaluate persistent airway symptoms after surgical therapy for double aortic arch. CONCLUSION. Airway narrowing is clearly shown on cross-sectional imaging in patients with persistent airway symptoms after surgical therapy for double aortic arch. Two patterns of airway compression are typically seen: narrowing of the trachea at the level of the postsurgical arch and narrowing of the left main bronchus as a result of compression from a midline descending aorta. Both patterns may be seen in patients regardless of whether the left or the right arch has been ligated. E xtrinsic tracheal compression caused by vascular rings, such as double aortic arch, can present with lifethreatening episodes of stridor, cyanosis, or apnea. Surgical correction of the underlying vascular ring has been shown to be an effective treatment for such patients, with 70 86% of patients having complete resolution of symptoms after the surgery [1 5]. However, as many as 30% of pediatric patients may have persistent airway symptoms after initial surgical relief of the vascular ring [1 5]. These symptoms may be related to tracheomalacia, persistent extrinsic airway compression, or a combination of the two. Some of these patients who have persistent symptoms may benefit from a second operation, such as aortopexy, other vascular suspension procedures, or airway resection or reconstruction [1, 2, 4]. In one series, 11% of patients required a second operation to relieve airway symptoms [1]. It has been suggested that the patient with persistent airway symptoms after surgical therapy of a vascular ring be evaluated with both bronchoscopy and cross-sectional imaging, such as MR imaging or helical CT [1, 2]. The purpose of our study was to review the imaging findings of children referred for cross-sectional imaging who had persistent airway symptoms after surgical therapy for double aortic arch. Materials and Methods We reviewed the records of CT and MR imaging examinations in pediatric patients referred to our institution to evaluate for extrinsic airway compression for persistent airway symptoms after surgery for double aortic arch. MR imaging studies from a 5-year period ( ) were reviewed. All MR imaging studies were performed on a 1.5-T scanner (General Electric Medical Systems, Milwaukee, WI) with sequences including, at minimum, T1-weighted images in the axial, sagittal, and coronal planes. CT examinations were reviewed from a 1-year period ( ) after the installation of a multidetector CT scanner (Light- Speed; General Electric Medical Systems). CT studies were performed after the administration of IV contrast material. CT parameters included 2.5- mm slice thickness; 120 kv; and weight-based, low-dose tube current [6]. Patient charts and imaging studies were reviewed in identified cases. Parameters recorded AJR:178, May

2 Fleck et al. TABLE 1 Summary of Findings in Four Patients with Persistent Airway Symptoms After Surgery for Double Aortic Arch Patient Age at Diagnosis Sex Arch Ligated Interval a CT or MR Imaging Findings Bronchoscopy Findings 1 2 days Male Left 13 years LMB compression at MDA b Fixed, pulsatile compression LMB 2 1 week Male Left 4 months Narrowing trachea at right arch; LMB compression at MDA b 3 1 week Male Right 1 year 5 months Narrowing trachea at left arch; LMB compression at MDA b Note. LMB = left main bronchus, MDA = midline descending aorta. a Time between surgical repair of the double aortic arch and time of reimaging. b MR imaging findings. c CT finding. included the age of the patient at the time of diagnosis of double aortic arch by imaging, the type of imaging performed (CT or MR imaging), the aortic arch ligated at surgery (left vs right), the duration of time between surgical repair of the double aortic arch and the time of reimaging, symptoms leading to reimaging, and treatment after imaging was performed. The imaging studies were reviewed for abnormal caliber of the airway and extrinsic structures causing compression at the level of airway narrowing. Patterns of extrinsic compression were reviewed between patients. Imaging findings were compared with findings seen at bronchoscopy. The retrospective review of this material was approved by our institutional review board. Results Our review of these studies yielded four patients (three males and one female, whose ages at diagnosis ranged from 2 days to 1 year) who had been referred for imaging because of persistent airway symptoms after surgical treatment for double aortic arch (Table 1). All patients had stridor or other noisy breathing. Two also experienced symptoms of obstructive sleep apnea. Two of the patients had poor growth and failure to thrive. Concerning the initial surgery, two of the patients had ligation of the left and two had ligation of the right aortic arch. The interval from the initial diagnosis and treatment of the double aortic arch and the request for reimaging ranged from 1 month to 13 years. All patients referred for imaging were evaluated with bronchoscopy during the same time period. MR imaging was used to evaluate the persistent symptoms in three patients and CT was used in one patient. All patients showed at least one area of abnormal airway caliber, and two patients had two discrete areas of abnormality. We found two discrete patterns of airway narrowing and extrinsic compression. Three patients had narrowing of the airway at the level of the remaining aortic arch. The airway narrowing was immediately abutting the intact aortic arch and the remaining anterior portion of the ligated arch that was retained to connect to the ipsilateral subclavian and common carotid arteries (Fig. 1). In two patients, the left arch was present, and in two patients the right arch was present. Three patients had narrowing of the left main bronchus. In all three patients, the descending aorta was in an abnormal midline position, immediately anterior to the spine, instead of in the typical paraspinal location. In such patients, the abnormal position of the descending aorta caused abnormal stacking of structures in the confined space between the spine and the manubrium, which led to compression of the left main bronchus between the abnormally positioned descending aorta posteriorly and the pulmonary arteries anteriorly (Fig. 2). Two of the patients required tracheotomy to treat their airway symptoms. Two patients were treated without surgery, but they did require continuous positive-pressure ventilation during sleep for treatment of their obstructive sleep apnea. Discussion Cross-sectional imaging has an important role in the evaluation of children with potential extrinsic airway compression, and MR imaging has traditionally been the imaging modality of choice in evaluating these patients [7, 8]. However, with the recent increases in speed of acquisition and multiplanar reformat capability, helical CT has begun to play an increasingly larger role Fixed, pulsatile compression trachea; fixed, pulsatile compression LMB Fixed, pulsatile compression trachea; fixed, pulsatile compression LMB 4 1 year Female Right 1 month Narrowing trachea at left arch c Fixed, pulsatile compression trachea in the evaluation of these patients [7]. CT now can usually provide all of the needed anatomic information on the potential of extrinsic airway compression that is provided by MR imaging but with a lower incidence of examinations in which sedation is required [9]. The choice of which modality is used CT or MR imaging is often made on an institutional basis. Cross-sectional imaging has also been shown to be helpful in the evaluation of potential extrinsic airway compression after surgical procedures [10]. As many as 30% of pediatric patients who undergo surgical therapy for vascular rings may have persistent airway symptoms [2]. In one review specifically of patients with double aortic arch, 24% had persistent airway symptoms after surgery. Cross-sectional imaging plays an important role in the evaluation of such patients [1, 2]. We have described the cross-sectional imaging findings in four patients who had persistent airway symptoms and were referred for cross-sectional imaging. All four of these patients had at least one area of airway narrowing seen on imaging and two of the patients had two discrete areas of narrowing shown. Two patterns of airway compression were identified, and these were not mutually exclusive. One pattern was extrinsic compression of the trachea at the level of the aortic arch. The intact arch and remaining anterior portion of the ligated arch were immediately abutting the airway at the level of narrowing consistent with extrinsic airway compression. The endoscopic evaluation also revealed fixed, pulsatile compression of the airway consistent with extrinsic compression, rather than tracheomalacia. We define tracheomalacia as an underlying weakness of the trachea, in the absence of extrinsic compression, that results in dynamic decrease in the airway caliber. A component of malacia, 1276 AJR:178, May 2002

3 Imaging Findings in Pediatric Patients After Surgery for Double Aortic Arch or airway wall weakening, is often associated with long-standing extrinsic airway compression. We are not able to exclude the presence of a concurrent component of airway wall weakening in addition to the extrinsic compression. It has been reported that patients with extrinsic airway compression after initial repair for double aortic arch do benefit from aortopexy, also suggesting that persistent extrinsic compression does play some role [1, 2, 4]. This pattern was seen both in patients who had the right arch ligated surgically and in those who had the left arch ligated, suggesting that the arch ligated is not a predisposing factor to developing this type of airway narrowing. The other pattern of airway narrowing identified was that of left main bronchus narrowing associated with a midline positioned descending aorta. Midline descending aorta was first described as a cause of airway compression in 1995 [11]. Other investigators then showed that a midline position of the descending aorta was more often present in children with left main bronchus compression than in nonsymptomatic patients [12]. Normally, the descending aorta sits in a paraspinal location. When the descending aorta lies immediately anterior to the spine, there is abnormal stacking of structures in the confined space between the A spine and the anterior chest wall. In such patients, the airway most typically the left main bronchus is extrinsically compressed between the abnormally positioned descending aorta posteriorly and the pulmonary arteries anteriorly [11]. Midline descending aorta airway compression syndrome has been described as an isolated lesion [11], but it has also been reported to occur as a phenomenon associated with hypoplastic right lung and resultant mediastinal shift or with a right arch and left-sided descending aorta [8]. Anatomically, patients with double aortic arch are probably prone to have a midline position of the descending aorta related to B C D Fig. 1. Airway compression at level of trachea in 1-year-old girl after repair of double aortic arch. A, Contrast-enhanced CT image obtained at time of initial diagnosis shows double aortic arch (arrowheads) with marked airway compression (arrow). B, Contrast-enhanced CT image obtained at time of reimaging 1 month after surgery shows trachea (large arrow) to be narrowed between left arch (small arrows) and persistent portion of right arch (arrowhead), which was retained to connect to right subclavian and common carotid arteries. C, Surface-rendered three-dimensional CT image shows narrowing (arrows) of caliber of trachea (T) at level of arch. Esophagus (E) is also dilated and air-filled above this level. Some aerated lung is also present. D, Endoscopic image shows narrowing of trachea (arrows) that is both fixed and pulsatile. AJR:178, May

4 Fleck et al. dual-sidedness of their bilateral arches. This pattern of airway compression was seen in patients with the left aortic arch ligated and in those with the right aortic arch ligated, suggesting that the pattern is independent of the dominant arch. In conclusion, we found that airway narrowing is clearly shown on cross-sectional imaging in patients with persistent airway symptoms after surgical therapy for double aortic arch. Such patients typically show two patterns of airway compression: narrowing of A the trachea at the level of the postoperative arch and narrowing of the left main bronchus caused by compression from a midline descending aorta. These patterns may be seen in patients regardless of whether the left or right arch was ligated. B C D Fig. 2. Airway compression at level of trachea and left main bronchus in 17month-old boy after repair of double aortic arch. A, CT image from time of initial diagnosis at 1 week of life shows double aortic arch compressing trachea. Left arch (arrows) is larger than right arch (arrowheads). Endotracheal tube is in trachea. Patient underwent surgical ligation of smaller, right arch. B, Axial T1-weighted MR image obtained after surgery at level of persistent left arch (A) and anterior segment of right arch (arrowhead) shows trachea (arrow) to be oblong and slightly narrowed. C, Endoscopic image shows fixed, pulsatile narrowing of trachea. D, Axial T1-weighted MR image obtained at lower level shows descending aorta (D) to be in midline position, immediately anterior to spine. Left main bronchus (arrow) is compressed between abnormally positioned descending aorta and right pulmonary artery (P) and is much narrower in diameter than right main bronchus (arrowhead). E, Endoscopic image, oriented as MR images in B and D, shows compression of left main bronchus (arrows), which is much smaller in diameter than right main bronchus (arrowheads). Narrowing was fixed and pulsatile. E 1278 AJR:178, May 2002

5 Imaging Findings in Pediatric Patients After Surgery for Double Aortic Arch References 1. Erwin EA, Gerber ME, Cotton RT. Vascular compression of the airway: indications for and results of surgical management. Int J Pediatr Otorhinolaryngol 1997;40: Anand R, Dooley KJ, Williams WH. Vincent RN. Follow-up of surgical correction of vascular anomalies causing tracheobronchial compression. Pediatr Cardiol 1994;15: Horvath P, Hucin B, Hruda J, et al. Intermediate to late results of surgical relief of vascular tracheobronchial compression. Eur J Cardiothorac Surg 1992;6: Han MT, Hall DG, Manche A, Rittenhouse EA. Double aortic arch causing tracheoesophageal compression. Am J Surg 1993;165: Sebening C, Jakob H, Tochtermann U, et al. Vascular tracheobronchial compression syndromes: experience in surgical treatment and literature review. Thorac Cardiovasc Surg 2000;48: Donnelly LF, Emery KH, Brody AS, et al. Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large children s hospital. AJR 2001;176: Katz M, Konen E, Rozenman J, Szeinberg A, Itzchak Y. Spiral CT and 3D image reconstruction of vascular rings and associated tracheobronchial anomalies. J Comput Assist Tomogr 1995;19: Donnelly LF, Strife JL, Bisset GS III. The spectrum of extrinsic lower airway compression in children: MR imaging. AJR 1997;168: Pappas JN, Donnelly LF, Frush DP. Reduced frequency of sedation of young children with multisection helical CT. Radiology 2000;215: Donnelly LF, Strife JL, Bailey WW. Extrinsic airway compression secondary to pulmonary arterial conduits: MR findings. Pediatr Radiol 1997;27: Donnelly LF, Bisset GS III, McDermott B. Anomalous midline location of the descending aorta: a cause of compression of the carina and left mainstem bronchus in infants. AJR 1995;164: Hungate RG, Newman B, Meza MP. Left mainstem bronchial narrowing: a vascular compression syndrome? Evaluation by magnetic resonance imaging. Pediatr Radiol 1998;28: Applications and papers for the ARRS Residents in Radiology Awards are now being accepted; the deadline is February Log on to for details. AJR:178, May