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Year : 2008  |  Volume : 18  |  Issue : 2  |  Page : 119-123
Pictorial essay: The utility of multi-detector computed tomography angiography post-repair of truncus arteriosus


Department of Pediatric Radiology, Arkansas Children's Hospital, University of Arkansas for Medical Sciences, 800 Marshall Street, Little Rock, Arkansas, 72202, USA

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How to cite this article:
Greenberg S B, Shah CC, Bhutta ST. Pictorial essay: The utility of multi-detector computed tomography angiography post-repair of truncus arteriosus. Indian J Radiol Imaging 2008;18:119-23

How to cite this URL:
Greenberg S B, Shah CC, Bhutta ST. Pictorial essay: The utility of multi-detector computed tomography angiography post-repair of truncus arteriosus. Indian J Radiol Imaging [serial online] 2008 [cited 2019 Aug 21];18:119-23. Available from: http://www.ijri.org/text.asp?2008/18/2/119/40291
Truncus arteriosus surgery includes ventricle septal defect (VSD) patch closure and removal of the pulmonary vasculature from the truncus. A conduit or homograft [1] connects the right ventricle to the pulmonary artery or branch pulmonary arteries. Stents are frequently placed in hypoplastic branch pulmonary arteries. Complications include outflow obstruction, branch pulmonary artery stenosis, and pulmonary regurgitation.

Echocardiography and magnetic resonance imaging (MRI) have established roles in the follow-up of patients following surgery for congenital heart disease. Echocardiography is the primary imaging modality for follow-up, but it has a limited role in the evaluation of conduits, prosthetic valves, and stents. The branch pulmonary arteries are frequently not well visualized. [2] MRI can evaluate morphology and function. However, its role is often limited by metal artifact. [2] MRI, unlike computed tomography, [3] is also insensitive in detecting conduit calcification.

Multi-detector computed tomography angiography (MDCTA) [4] is easier to perform than magnetic resonance angiography (MRA) and has better spatial resolution. [5],[6] Metal artifacts are less severe than with MRI. Our aim is to illustrate the utility of CTA in the follow-up of patients following surgery for truncus arteriosus.


   Subjects and Methods Top


This essay is based on a retrospective study that was approved by the university institutional review board. The study included eight consecutive patients with truncus arteriosus repair who underwent MDCTA examination at a tertiary children's hospital between April 2004 and August 2006. Echocardiography was performed in all these patients. None of them underwent MRI. Seven patients had type I truncus arteriosus and one patient had type II truncus arteriosus. The indications for choosing MDCTA over MRA are noted in [Table - 1]. Indications included presence of metallic stents or conduits, a prosthetic valve, or pacemaker wires in six patients. Respiratory distress and acute illness were the indications in the other two patients. Patients ranged in age from 1 month to 24 years, with a mean age of 8.2 years.

All scans were performed using a Toshiba Aquillion 16-slice scanner (Otawara, Japan). A dual-head power injector was used for all studies. The route of injection for contrast injection was an upper limb vein in all cases. Iohexol intravenous contrast (Omnipaque; Amersham, Cork, Republic of Ireland) was used in two concentrations. Omnipaque 320 was used in six patients who received a total dose of 2 ml/kg. Omnipaque 240 was used in two infants to allow for an increased contrast volume. These children received 3 ml/kg. The injection rate used was 1 to 3 ml/s, depending on the size of the patient. Saline flush was used to advance the contrast bolus in all patients. Scanning was initiated using bolus tracking in the descending thoracic aorta since it was easily identified in all our patients, as compared to the unopacified ascending aorta, which is often difficult to identify due to the complex anatomy. The scan technique allowed for opacification of the pulmonary arteries and aorta. Scans were performed using 0.5 or 1.0 mm collimation and 0.4 s tube rotation. Four patients had gated studies and four had ungated studies. The decision to cardiac-gate was based on the clinical needs of the particular patient. If aortic or conduit root anatomy, coronary artery anatomy, or cardiac function were a high priority, cardiac gating was used. If the region of interest was a branch pulmonary artery, no cardiac gating was used. Age and heart rate were not determining factors for gating. Breath-hold was used for patients who were old enough to cooperate. Intubation was used for younger children who could not cooperate. The kVp ranged from 80 to 120 and the mAs ranged from 80 to 160, depending on patient size. Age and technique for each patient are summarized in [Table - 1].

Axial images were reconstructed at 0.5-1 mm slice thickness without a gap. A soft tissue computer reconstruction algorithm was used (Toshiba FC 12). All patients had additional multiplanar reformations and three-dimensional volume renderings created using Vitrea (VITAL Images, Inc. Minnetonka, Minnesota, USA) and CAW GE (GE Healthcare, Milwaukee, WI, USA) workstations. The image quality was evaluated by two pediatric radiologists with respect to metal-related motion or streak artifacts. The studies were evaluated for their ability to detect normal post-operative anatomy, abnormal calcifications, stenoses, stents, prosthetic valves, or associated abnormalities. Each scan was categorized as nondiagnostic, degraded but diagnostic, or of excellent quality.


   Results Top


Seven of eight studies had excellent quality imaging. One examination was diagnostic but had degraded image quality due to poor bolus timing. Scanning was delayed due to human error, leading to suboptimal vascular opacification. The presence of calcification, metal clips, stents, and a prosthetic valve did not cause image degradation to an extent that could impede interpretation in any of the patients.

The findings are summarized in [Table - 2]. Branch pulmonary artery stenosis was identified in five patients; there was right pulmonary stenosis in three patients and left pulmonary stenosis in three patients [Figure - 1],[Figure - 2]. Three branch pulmonary stents were identified. A left branch pulmonary stent was outgrown with the branch pulmonary artery diameter proximal and distal to the stent being greater [Figure - 3]. Proximal stenosis in a right branch pulmonary artery stent was identified [Figure - 4]. No intimal thickening or complete obstruction of the stents was present. Pulmonary conduit or graft stenosis was identified in two patients. Two patients also had graft calcification [Figure - 5]A, B. One prosthetic St. Jude valve in the aortic valve position was small, relative to the subaortic area and aortic root [Figure - 5]C, D. Coronary artery anomalies were detected in two patients [Figure - 5]E. Bilateral main stem bronchus stenosis was detected in one patient [Figure - 6].


   Discussion Top


Truncus arteriosus surgery includes creation of a neoaorta by closing the VSD and isolating the pulmonary artery or branch pulmonary arteries from the truncus. A conduit or graft is sewn to the right ventricle free wall and the pulmonary artery or branch pulmonary arteries. Complications include valve insufficiency, stenosis, and obstruction. Artificial valves, homografts, conduits, and metal stents can become stenotic due to patient growth. Identification of intimal thickening and stenosis of stents is important for patient management. [7]

Following repair, the branch pulmonary arteries are often difficult to visualize on echocardiography. Conventional angiography requires ionizing radiation and is invasive. MRI is the preferred modality if there is no stent. In the presence of stents, artifacts limit evaluation on MRI. Stents, however, do not produce artifacts on MDCT. Patients with contraindications to MRI, such as those with pacemakers, can also safely undergo MDCT examination. MDCT examinations are faster and provide higher spatial resolution than MRI.

Ionizing radiation is a significant concern in MDCTA. Therefore, MDCTA was performed only in patients who were not good candidates for MRI due to the presence of metal that would create unacceptable artifacts, cardiac pacemaker leads, acute illness, or the need for simultaneous evaluation of the airway.

Our study demonstrates the utility of MDCTA in the follow-up of truncus arteriosus. No significant image degradation resulted from the presence of a prosthetic valve, metal stent, or graft calcification. The study successfully detected conduit and branch pulmonary artery stenosis and mental stents. A prosthetic valve was well seen, too. Coronary artery anomalies were detected in two of our patients and these are better evaluated by MDCTA than by echocardiography or MRA. [8] One patient had bilateral bronchial stenosis. Multiplanar reformations and 3D volume renderings of the same dataset as the CTA allow for excellent depiction of the trachea and bronchi.


   Conclusion Top


MDCTA is effective for the evaluation of patients following repair of truncus arteriosus. MDCTA allows evaluation of the post-operative anatomy, prosthetic valves, branch pulmonary artery stents, coronary artery anomalies, and airway stenoses.

 
   References Top

1.Brown JW, Ruzmetov M, Rodefeld, Vijay P, Darragh RK. Valved bovine jugular vein conduits for right ventricular outflow tract reconstruction in children: An attractive alternative to pulmonary homograft. Ann Thorac Surg 2006;82:909-16.  Back to cited text no. 1    
2.Eichhorn JG, Long FR, Hill SL, O'Donovan J, Chisolm JL, ­Fernandez SA, et al . Assessment of in-stent stenosis in small children with congenital heart disease using multi-detector computed tomography: A validation study. Catheter Cardiovasc Interv 2006;68:11-20.  Back to cited text no. 2    
3.Leschka S, Oechslin E, Husman L, Desbiolles L, Marincek B, ­Genoni M, et al . Pre- and postoperative evaluation of congenital heart disease in children and adults with 64-Section CT. Radiographics 2007;27:829-46.  Back to cited text no. 3    
4.Lee T, Tsai I, Fu Y, Jan S, Wang C, Chang Y, et al . Using multidetector-row CT in neonates with complex congenital heart disease to replace diagnostic cardiac catheterization for anatomical investigation: Initial experiences in technical and clinical feasibility. Pediatr Radiol 2006;36:1273-82.  Back to cited text no. 4    
5.Ley S, Zaporozhan J, Arnold R, Eichhorn J, Schenk J, Ulmer H, et al . Preoperative assessment and follow-up of congenital abnormalities of the pulmonary arteries using CT and MRI. Eur Radiol 2007;17:151-62.  Back to cited text no. 5    
6.Bean MJ, Pannu H, Fishman EK. Three-dimensional computed tomographic imaging of complex congenital cardiovascular abnormalities. J Comput Assist Tomogr 2005;29:721-4.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]
7.Sato Y, Matsumoto N, Komatsu S, Kunimasa T, Yoda S, Kunimoto S, et al . MDCT evaluation of the right ventricle-pulmonary artery bypass stenosis in corrected tetralogy of Fallot. Int J Cardiol 2007;115:267-9.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Kantarci M, Koplay M, Bayraktutan U, Gundogdu F, Ceviz N. Congenitally corrected transposition of the great arteries: MDCT angiography findings and interpretation of complex coronary anatomy. Int J Cardiovasc Imaging 2007;23:405-10.  Back to cited text no. 8  [PUBMED]  [FULLTEXT]

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Correspondence Address:
Chetan Chandulal Shah
Pediatric Radiology, Arkansas Children's Hospital, University of Arkansas for Medical Sciences, 800 Marshall Street, Little Rock, Arkansas 72202
USA
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.40291

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  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]
 
 
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